Category: Precision Oncology

FDA Approves ENHERTU® for Neoadjuvant Therapy in High-Risk HER2-Positive Early Breast Cancer

RR

SUMMARY: The FDA on May 15, 2026, approved fam-Trastuzumab deruxtecan-nxki (T-DXd, ENHERTU®), followed by a taxane, Trastuzumab, and Pertuzumab (THP) for the neoadjuvant treatment of adult patients with HER2-positive (IHC 3+ or ISH+) Stage II or III breast cancer, as determined by an FDA-authorized test. FDA also approved two companion diagnostic devices, the PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody and the VENTANA HER2 Dual ISH DNA Probe Cocktail, both for identifying HER2-positive (IHC3+ or ISH+) patients for treatment with T-DXd, consistent with the approved drug labeling.

Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

Human Epidermal growth factor Receptor 2–positive (HER2+) breast cancer accounts for approximately 15%-20% of all breast malignancies and historically has been associated with aggressive disease biology. Over the past decade, the integration of dual HER2 blockade with Trastuzumab (HERCEPTIN®) and Pertuzumab (PERJETA®) alongside cytotoxic chemotherapy has substantially improved outcomes. In patients with Stage II–III disease, neoadjuvant therapy has become the standard treatment approach, enabling early assessment of treatment response and guiding postoperative therapy.

The present FDA approval was based on DESTINY-Breast11 trial, which explored whether Antibody-Drug Conjugate (ADC)-based therapy, could improve efficacy, while reducing the toxicity burden associated with traditional Anthracycline and Carboplatin containing regimens.

Trial Design and Patient Population

DESTINY-Breast11 was a global, multicentre, open-label Phase III study conducted across 147 sites in 18 countries. The trial enrolled patients with high-risk, locally advanced, or inflammatory HER2-positive early-stage breast cancer, defined by lymph node-positive disease (N1-3) or primary tumors staged T3-4.

A total of 927 female patients were randomized across three treatment arms:

Patients assigned to the investigational combination arm received T-DXd 5.4 mg/kg intravenously every 3 weeks for four cycles followed by Paclitaxel 80 mg/m² weekly, Trastuzumab 6 mg/kg every 3 weeks and Pertuzumab 840 mg loading dose followed by 420 mg every 3 weeks for 4 cycles (T-DXd followed by THP; N=321)

The comparator arm received Dose-dense Doxorubicin 60 mg/m² every 2 weeks, Cyclophosphamide 600 mg/m² every 2 weeks for four cycles, followed by Paclitaxel 80 mg/m² weekly with concurrent Trastuzumab 8 mg/kg loading dose followed by 6 mg/kg every 3 weeks Pertuzumab 840 mg loading dose, followed by 420 mg every 3 weeks for 4 cycles. (Dose-dense AC followed by THP (ddAC-THP; N=320)

The T-DXd monotherapy arm evaluated eight cycles of T-DXd at 5.4 mg/kg every 3 weeks; however, enrollment into this cohort was discontinued early following an Independent Data Monitoring Committee (IDMC) review (T-DXd monotherapy; N=286)

Median patient age was 50 years, 88% had an ECOG performance status of 0, and approximately 72% had Hormone Receptor (HR)-positive disease. HER2 expression was strongly positive in most patients, with 88% classified as IHC 3+.

Primary Endpoint Met with Significant pCR Improvement

The Primary endpoint was centrally assessed pathological Complete Response (pCR), defined as ypT0/is ypN0 following surgery.

Results demonstrated 67.3% pCR rate with T-DXd-THP vs 56.3% with ddAC-THP. This translated into an absolute improvement of 11% (95% CI: 4.0%-18.3%; P=0.003). Importantly, benefit was observed across hormone receptor subgroups:

  • HR-positive disease: 61.4% vs 52.3%
  • HR-negative disease: 83.1% vs 67.1%

The magnitude of benefit in the HR-negative cohort was particularly notable, with an absolute pCR improvement exceeding 16%. Investigators also reported improved Residual Cancer Burden (RCB) outcomes with T-DXd-THP, with RCB-0/I rates reaching 81.3% compared with 69.1% for the standard regimen.

Early EFS Signal and Safety Advantages

While Event-Free Survival (EFS) data remain immature, early findings favored the investigational approach. At 4.5% maturity, the Hazard Ratio for EFS comparing T-DXd-THP with ddAC-THP was 0.56 (95% CI: 0.26-1.17). Equally important for clinical practice, the ADC-based regimen demonstrated a more favorable toxicity profile than the anthracycline-containing comparator.

Grade ≥3 adverse events occurred in 37.5% of patients receiving T-DXd-THP vs 55.8% with ddAC-THP. Serious adverse events were also reduced and occurred in 10.6% with T-DXd-THP vs 20.2% with ddAC-THP. Cardiac toxicity rates were lower with the investigational regimen, with all-grade left ventricular dysfunction reported in only 1.3% of patients receiving T-DXd-THP compared with 6.1% in the ddAC-THP arm.

Given ongoing concerns regarding anthracycline-associated cardiotoxicity, these findings may be particularly relevant when selecting therapy for patients with baseline cardiovascular risk factors.

Interstitial lung disease (ILD)/pneumonitis, an established toxicity associated with T-DXd, was infrequent and comparable across treatment groups, occurring in approximately 4%-5% of patients. Three treatment-related deaths were reported overall.

Closure of the T-DXd Monotherapy Arm

Although the T-DXd monotherapy arm passed a predefined futility analysis, enrollment was halted early after IDMC review. Investigators cited multiple contributing factors, including lower pCR rates, reduced likelihood of superiority over standard therapy, and timing considerations surrounding surgery. Observed pCR rates were 43.0% with T-DXd alone, 67.3% with T-DXd-THP, and 56.3% with ddAC-THP. Interpretation of the monotherapy cohort was further complicated by protocol-directed transitions to local standard-of-care therapy after enrollment closure.

Clinical Implications

DESTINY-Breast11 introduces compelling evidence supporting ADC-based neoadjuvant therapy in high-risk HER2-positive early breast cancer. The combination of T-DXd followed by THP not only improved pCR rates compared with an anthracycline-based standard but also reduced severe toxicities and cardiac adverse events.

The findings are especially notable given the trial’s predominantly HR-positive and high-risk patient population, where pCR rates are historically more difficult to achieve. As clinicians continue to balance efficacy against long-term toxicity risks, DESTINY-Breast11 raises the possibility that Anthracycline- and Carboplatin-free regimens may emerge as a new treatment paradigm for selected patients with HER2-positive early-stage disease. Longer follow-up will be essential to determine whether the substantial pCR gains observed in DESTINY-Breast11 ultimately translate into durable improvements in Event-Free and Overall Survival.

Neoadjuvant trastuzumab deruxtecan alone or followed by paclitaxel, trastuzumab, and pertuzumab for high-risk HER2-positive early breast cancer (DESTINY-Breast11): a randomised, open-label, multicentre, phase III trial. Harbeck N, Modi S, Pusztai L, et al., for the DESTINY-Breast11 Trial Investigators. Annals of Oncology, 2025; 37:166-179.

FDA Approves ENHERTU® in Postneoadjuvant Care for High-Risk HER2-Positive Early Breast Cancer

RR

SUMMARY: The FDA on May 15, 2026, approved fam-Trastuzumab deruxtecan-nxki (T-DXd, ENHERTU®) for the adjuvant treatment of adult patients with HER2-positive (IHC 3+ or ISH+) breast cancer who have residual invasive disease following neoadjuvant treatment with Trastuzumab (with or without Pertuzumab) and taxane-based treatment.

FDA also approved two companion diagnostic devices, the PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody and the VENTANA HER2 Dual ISH DNA Probe Cocktail, both for identifying HER2-positive (IHC3+ or ISH+) patients for treatment with T-DXd, consistent with the approved drug labeling.

Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

Background: Escalation Strategies in Residual Disease

The management of HER2-positive early breast cancer has undergone a profound transformation over the past two decades, driven by the integration of HER2-directed therapies across disease stages. In patients with Stage II–III disease, neoadjuvant therapy has become the standard treatment approach, enabling early assessment of treatment response and guiding postoperative therapy. Despite high rates of pathologic Complete Response (pCR) with contemporary neoadjuvant regimens, a clinically significant subset of patients exhibits residual invasive disease at surgery, an established marker of elevated recurrence risk.

The paradigm of risk-adapted postneoadjuvant therapy was firmly established by the KATHERINE trial, in which Trastuzumab emtansine (T-DM1-KADCYLA®) demonstrated a substantial improvement in Invasive Disease–Free Survival (IDFS) and Overall Survival (OS), compared with Trastuzumab alone. However, outcomes in higher-risk subgroups, particularly those with node-positive or extensive residual disease remain suboptimal, and CNS relapses continue to represent an unmet need.

Trastuzumab deruxtecan (T-DXd-ENHERTU®), a next-generation HER2-directed antibody–drug conjugate, has consistently demonstrated superior efficacy over T-DM1 in the metastatic setting, including activity in CNS disease. These data provided a strong rationale to evaluate whether T-DXd could further improve outcomes in the curative-intent, postneoadjuvant setting.

Trial Design and Patient Population

The present FDA approval was based on DESTINY-Breast05, which is a global, Phase III, open-label, randomized trial evaluating T-DXd versus T-DM1 in patients with HER2-positive early breast cancer and residual invasive disease following neoadjuvant therapy, enriched for high-risk features.

Eligible patients had:

  • Residual invasive disease in breast and/or axillary nodes
  • Either inoperable disease at presentation or node-positive disease after neoadjuvant therapy
  • Prior receipt of standard neoadjuvant systemic therapy, including taxane-based chemotherapy and HER2-targeted therapy

A total of 1635 patients were randomized 1:1 to receive T-DXd (5.4 mg/kg) every 3 weeks (N=818) or T-DM1 (3.6 mg/kg) every 3 weeks (N=817) for up to 14 cycles. The Primary endpoint was invasive DFS (IDFS), with key Secondary endpoints including DFS, distant recurrence, CNS outcomes, and Overall Survival (OS). Notably, this trial enrolled a higher-risk population than prior studies: About 52% presented with inoperable disease at disease presentation, about 81% had node-positive disease after neoadjuvant therapy and approximately 79% received dual HER2 blockade preoperatively.

Efficacy: A New Benchmark for Invasive Disease–Free Survival

At a median follow-up of approximately 30 months, T-DXd demonstrated a clinically and statistically significant improvement in outcomes compared with T-DM1:

    • IDFS events or death: 6.2% (T-DXd) vs. 12.5% (T-DM1); Hazard ratio (HR): 0.47 (P<0.001)
    • 3-year IDFS: 92.4% vs. 83.7%
    • 3-year DFS: 92.3% vs. 83.5% (HR: 0.47)

The benefit was consistent across prespecified subgroups, including hormone receptor–positive disease driven largely by a reduction in distant recurrences, the dominant mode of failure. Importantly, the distant recurrence: 5.1% vs. 9.9% and CNS recurrence was numerically lower with T-DXd (2.1% vs. 3.1%)

Although Overall Survival data remain immature, the magnitude of IDFS improvement strongly supports a meaningful long-term benefit.

Safety Profile: Balancing Efficacy with Toxicity

The safety profiles of both agents were consistent with prior experience, though distinct in nature. The common adverse events with T-DXd included nausea (71%), neutropenia, vomiting and alopecia. Approximately 50% of patients had grade ≥3 adverse events. T-DM1 was associated with hepatotoxicity (elevated transaminases) and thrombocytopenia.

Key Safety Signal: Interstitial Lung Disease (ILD)

The most clinically significant toxicity associated with T-DXd remains ILD. The incidence was 9.6% (T-DXd) vs. 1.6% (T-DM1). They were mostly grade 1–2, but grade ≥3 events occurred and two treatment-related deaths reported. The trial incorporated proactive ILD monitoring, including serial low-dose chest CT imaging, enabling early detection. Importantly no increased ILD risk was observed with concurrent radiotherapy. Multidisciplinary evaluation is critical to distinguish ILD from radiation pneumonitis.

Clinical Context: Positioning Within Current Practice

These findings represent a clear evolution beyond the KATHERINE standard, particularly in a more contemporary, higher-risk population treated with modern neoadjuvant regimens.

Implications for Clinical Practice

  • T-DXd emerges as the preferred postneoadjuvant therapy for patients with:
    • Residual invasive disease
    • Node-positive or otherwise high-risk features
  • T-DM1 remains relevant for:
    • Lower-risk residual disease
    • Patients unable to tolerate T-DXd

Conclusions

DESTINY-Breast05 establishes Trastuzumab deruxtecan as a new standard of care in the postneoadjuvant management of high-risk HER2-positive early breast cancer with residual disease. The trial demonstrates a substantial and clinically meaningful improvement in Invasive Disease–Free Survival, a reduction in distant recurrence and manageable but clinically significant toxicity, particularly interstitial lung disease.

As the field moves toward increasingly personalized, response-adapted strategies, T-DXd represents a major advance, while underscoring the need for vigilant toxicity monitoring and multidisciplinary care in the curative setting.

Trastuzumab Deruxtecan in Residual HER2-Positive Early Breast Cancer. Loibl S, Park YH, Shao Z, et al. for the DESTINY-Breast05 Trial Investigators. N Engl J Med 2026;394:845-857.

FDA Approves Next Generation Vepdegestrant for ER-positive, HER2-negative, ESR1-Mutated Advanced Breast Cancer

RR

SUMMARY: The FDA on May 1, 2026, approved Vepdegestrant (VEPPANU®), a heterobifunctional protein degrader, for adults with Estrogen Receptor (ER)-positive, Human Epidermal growth factor Receptor 2 (HER2)-negative, ESR1-mutated advanced or metastatic breast cancer, as detected by an FDA-authorized test, with disease progression following at least one line of endocrine therapy. FDA also approved the Guardant360 CDx as a companion diagnostic device to identify patients with breast cancer with ESR1 mutations for treatment with Vepdegestrant.

Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 316,950 new cases of female breast cancer will be diagnosed in 2025, and about 42,170 women will die of the disease, largely due to metastatic recurrence.

Background and Clinical Unmet Need
Approximately 70% of breast tumors express Estrogen Receptors and/or Progesterone Receptors. The most common subtype of metastatic breast cancer is Hormone Receptor-positive (HR-positive), HER2-negative breast cancer (65% of all metastatic breast tumors), and these patients are often treated with anti-estrogen therapy as first line treatment. However, resistance to hormonal therapy occurs in a majority of the patients, with a median Overall Survival (OS) of 36 months. With the development of Cyclin Dependent Kinases (CDK) 4/6 inhibitors, endocrine therapy plus a CDK4/6 inhibitor is the mainstay, for the management of ER+/HER2-negative metastatic breast cancer, as first line therapy. Even with this therapeutic combination, most patients will eventually experience disease progression, with up to 50% of patients acquiring ESR1 (Estrogen Receptor gene alpha) mutations after exposure to prior endocrine therapy in combination with CDK4/6 inhibitors. These mutations enable constitutive activation of the estrogen receptor, rendering tumors less responsive to traditional endocrine agents. Although Selective Estrogen Receptor Degraders (SERDs) such as Fulvestrant and Elacestrant are often used in this setting, their clinical activity is modest and limited by pharmacokinetic and mechanistic constraints, especially in heavily pretreated, endocrine-resistant disease.

A Novel Approach: Vepdegestrant and the PROTAC Platform
Vepdegestrant represents a first-in-class, oral PROteolysis TArgeting Chimera (PROTAC) designed to degrade the ER through direct engagement of the ubiquitin-proteasome system. Unlike traditional SERDs, which bind to and inactivate the ER before relying on indirect degradation pathways, Vepdegestrant forms a ternary complex between the ER and an E3 ubiquitin ligase. This results in efficient and targeted ubiquitination and subsequent degradation of the ER protein. Early-phase trials demonstrated that Vepdegestrant was well tolerated and exhibited promising antitumor activity in patients with heavily pretreated ER+/HER2-negative advanced breast cancer. This laid the foundation for VERITAC-2, the first Phase 3 study evaluating a PROTAC agent in oncology.

VERITAC-2: Study Design and Patient Population
Study Overview:
VERITAC-2 is a global, randomized Phase 3 trial comparing oral Vepdegestrant 200 mg once-daily continuously with Fulvestrant 500 mg intramuscularly days 1 and 15 of cycle 1 and day 1 of subsequent cycles, in postmenopausal women and men with ER+/HER2-negative advanced breast cancer, previously treated with a CDK4/6 inhibitor plus endocrine therapy. An additional line of endocrine therapy was permitted. However, patients previously exposed to SERDs or chemotherapy in the metastatic setting were excluded. A total of 624 patients (median age 60 years; 43%; N=270 with ESR1mutation tumors) were randomized 1:1 to receive Vepdegestrant (N=313) or Fulvestrant (N=311). Approximately 80% were postmenopausal, and 20% had received two prior lines of therapy in the advanced setting. Patients were stratified by ESR1 mutation status and presence of visceral disease. ESR1 mutational status was determined by blood circulating tumor DeoxyriboNucleic Acid (ctDNA) using central or local testing.

The Primary endpoint was Progression-Free Survival (PFS) as assessed by Blinded Independent Central Review (BICR), first in the ESR1mutations subgroup and then in the overall population contingent on statistical assumptions. Secondary endpoints included Overall Survival (OS), Objective Response Rate (ORR), Clinical Benefit Rate (CBR), and Safety.

Key Efficacy Findings

In the ESR1-Mutant Population:

  • Median PFS: 5.0 months with Vepdegestrant vs 2.1 months with Fulvestrant
  • Hazard Ratio: 0.57 (95% CI, 0.42–0.77); P=0.0001
  • 6-Month PFS Rate: 45.2% with Vepdegestrant vs 22.7% with Fulvestrant
  • Objective Response Rate: 18.6% vs 4.0% (P=0.001)
  • Clinical Benefit Rate: 42.1% vs 20.2% (P<0.001)

There was a 43% relative reduction in the risk of disease progression or death with Vepdegestrant compared with Fulvestrant. These results represent a statistically significant and clinically meaningful improvement in PFS and response outcomes among ESR1mutated patients, reinforcing the hypothesis that targeted ER degradation via PROTAC technology can overcome a key mechanism of endocrine resistance.

In the Overall Population:

  • Median PFS: 3.7 months (Vepdegestrant) vs 3.6 months (Fulvestrant)
  • HR: 0.83 (95% CI, 0.68–1.02); P=0.07

Although trends favored Vepdegestrant, the PFS difference in the unselected population did not reach statistical significance, underscoring the critical role of ESR1 mutation status as a biomarker of response to this agent.

Safety and Tolerability
Vepdegestrant was generally well tolerated, with most Adverse Events (AEs) being Grade 1 or 2. Grade 3 or more Treatment-Emergent AEs occurred in 23.4% receiving Vepdegestrant versus 17.6% with Fulvestrant. The most toxicities with Vepdegestrant were fatigue, elevated ALT/AST, nausea, vomiting and diarrhea. Discontinuation due to AEs occurred in only 2.9% of patients receiving Vepdegestrant. Importantly, gastrointestinal side effects, often limiting with oral SERDs, were infrequent and generally low-grade, reflecting the favorable tolerability of this novel agent.

Clinical Implications and Future Directions
The VERITAC-2 trial offers a landmark clinical validation for PROTACs in oncology. For patients with ER+/HER2-negative advanced breast cancer harboring ESR1 mutations, Vepdegestrant offers a statistically significant and clinically relevant advantage in Progression-Free Survival over Fulvestrant. The favorable safety profile, oral dosing convenience, and mechanistic novelty support its development as a next-generation standard of care in this biomarker-defined subgroup.

Although benefit was not observed in the all-comer population, the compelling results in ESR1mutated disease position Vepdegestrant as a precision endocrine therapy option that could reshape the treatment landscape. Ongoing investigations will clarify its role in earlier lines of therapy and in combination strategies, including with targeted or immunotherapeutic agents.

Conclusion
Vepdegestrant has emerged as a promising, targeted therapy for patients with ESR1-mutated ER+/HER2-negative advanced breast cancer who have progressed on prior CDK4/6 inhibitor plus endocrine therapy. As the first PROTAC to reach Phase 3, its success in VERITAC-2 signals the clinical viability of targeted protein degradation platforms in hormone receptor–driven malignancies.

Vepdegestrant, a PROTAC Estrogen Receptor Degrader, in Advanced Breast Cancer. Campone M, De Laurentiis M, Jhaveri K, et al. for the VERITAC-2 Study Group. N Engl J Med. 2025;393:556-568.

Reconsidering Menopausal Hormone Therapy in BRCA1/2 Carriers: Emerging Evidence Challenges Longstanding Concerns

RR

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

The tumor suppressor genes such as BRCA1 and BRCA2 help repair damaged DNA and thus play an important role in maintaining cellular genetic integrity, failing which these genetic aberrations can result in malignancies. Mutations in BRCA1 and BRCA2 account for about 20 to 25 percent of hereditary breast cancers and about 5 to 10 percent of all breast cancers. These mutations can be inherited from either of the parents and a child has a 50 percent chance of inheriting this mutation, and the deleterious effects of the mutations are seen even when a second copy of the gene in an individual is normal. Women with germline BRCA1 or BRCA2 mutations face markedly elevated lifetime risks of breast cancer, estimated at up to 70%. More than half of these cancers occur before the age of 50, underscoring the importance of informed counseling regarding risk-modifying exposures. 

For much of the latter half of the 20th century, Hormone Replacement Therapy (HRT) was widely prescribed to alleviate menopausal symptoms and protect against long-term complications such as osteoporosis. This practice shifted dramatically in 2002, when the Women’s Health Initiative reported increased risks of cardiovascular events and breast cancer associated with hormone therapy in older, postmenopausal women. In the aftermath, both patients and clinicians largely retreated from Menopausal Hormone Therapy (MHT), and its use declined sharply.

While those findings reshaped care in the general population, their applicability to women with hereditary cancer predisposition, particularly carriers of pathogenic BRCA1 or BRCA2 variants, has remained uncertain. These women face markedly elevated risks of ovarian and fallopian tube cancers and are therefore advised to undergo risk-reducing bilateral salpingo-oophorectomy at relatively young ages. The procedure is effective for cancer prevention but induces abrupt surgical menopause, often decades earlier than natural menopause, with well-documented short- and long-term consequences including vasomotor symptoms, sexual dysfunction, bone loss, and adverse cardiovascular and cognitive effects.

Menopausal Hormone Therapy (MHT) is the most effective intervention for mitigating these outcomes of early menopause. However, concerns that hormone exposure could further increase breast cancer risk in BRCA carriers have led to substantial hesitation, misinformation, and, in many cases, prolonged untreated symptoms. Researchers have emphasized, recommending premenopausal oophorectomy without offering a safe strategy to manage its consequences creates an untenable clinical dilemma.

Study Design: Emulating a Trial in a High-Risk Population

To address this evidence gap, investigators conducted the largest prospective matched analysis to date examining MHT use and breast cancer risk in BRCA1 and BRCA2 carriers. Using data from a longitudinal cohort, the study sought to emulate a randomized clinical trial by carefully matching women who initiated MHT after menopause, predominantly surgical menopause, to those who did not.

Eligible participants had no prior cancer history, no bilateral mastectomy, and had entered menopause. A total of 676 matched pairs were created, matched one-to-one by gene mutation (BRCA1 or BRCA2), year of birth, and age at menopause. Participants ranged in age from 22 to 76 years, with a mean age of 43.8 years. MHT formulations initiated after menopause included estrogen-only therapy, combined estrogen–progestogen therapy, progestogen alone, tibolone, and conjugated equine estrogen plus bazedoxifene. Cox proportional hazards models were used to estimate breast cancer risk.

Results: No Signal of Increased Breast Cancer Risk

After a mean follow-up of 5.6 years from the date of first MHT use, breast cancer incidence was significantly lower among women who used MHT compared with their matched, unexposed counterparts. Incident breast cancer occurred in 12.9% of MHT users versus 18.9% of non-users (P = 0.002).

Notably, estrogen-only therapy was associated with a substantial reduction in breast cancer risk, corresponding to a 63% relative decrease compared with non-users (HR=0·37; 95%: CI 0·24-0·57). In contrast, no increased or decreased risk was observed with combined estrogen–progestogen therapy, progestogen monotherapy, or tibolone. Among the 43 women who received conjugated equine estrogen plus bazedoxifene, no breast cancer diagnoses were reported during follow-up, an exploratory finding that warrants further investigation. Importantly, risk estimates were consistent across BRCA1 and BRCA2 carriers, underscoring the relevance of these findings across mutation subtypes.

Clinical Implications

These data provide critical reassurance for clinicians managing young women with hereditary breast and ovarian cancer syndromes. In contrast to earlier studies conducted in the general population, MHT use in BRCA1/2 carriers was not associated with an increased risk of breast cancer, regardless of formulation. Estrogen-only regimens, in particular, appeared protective, although causality cannot be inferred.

While limitations include a relatively modest follow-up duration and small numbers in certain subgroups, this prospective analysis offers the strongest evidence to date supporting the safety of MHT in this high-risk population. The findings reinforce the need for individualized, evidence-based counseling that balances cancer risk reduction with quality-of-life preservation.

Moving Forward

As MHT formulations continue to evolve, ongoing research will be essential to refine risk stratification and optimize menopause management strategies in BRCA mutation carriers. For now, these results support a personalized approach to MHT use in women experiencing surgical or natural menopause after risk-reducing oophorectomy, provided there are no contraindications. For many patients, informed use of MHT may offer not only symptom relief, but also a path toward improved long-term health and wellbeing without compromising breast cancer risk.

Menopausal Hormone Therapy and the Risk of Breast Cancer in Women with a Pathogenic Variant in BRCA1 or BRCA2. Kotsopoulos J, Seca M, Gronwald J, et al. J Natl Cancer Inst. 2025 Dec 17:djaf363. doi: 10.1093/jnci/djaf363. Epub ahead of print. PMID: 41403285.

DESTINY-Breast05: A New Direction in Postneoadjuvant Care for High-Risk HER2-Positive Early Breast Cancer

RR

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

Background: Escalation Strategies in Residual Disease

The management of HER2-positive early breast cancer has undergone a profound transformation over the past two decades, driven by the integration of HER2-directed therapies across disease stages. In patients with Stage II–III disease, neoadjuvant therapy has become the standard treatment approach, enabling early assessment of treatment response and guiding postoperative therapy. Despite high rates of pathologic Complete Response (pCR) with contemporary neoadjuvant regimens, a clinically significant subset of patients exhibits residual invasive disease at surgery, an established marker of elevated recurrence risk.

The paradigm of risk-adapted postneoadjuvant therapy was firmly established by the KATHERINE trial, in which Trastuzumab emtansine (T-DM1-KADCYLA&reg;) demonstrated a substantial improvement in Invasive Disease–Free Survival (IDFS) and Overall Survival (OS), compared with Trastuzumab alone. However, outcomes in higher-risk subgroups, particularly those with node-positive or extensive residual disease remain suboptimal, and CNS relapses continue to represent an unmet need.

Trastuzumab deruxtecan (T-DXd-ENHERTU&reg;), a next-generation HER2-directed antibody–drug conjugate, has consistently demonstrated superior efficacy over T-DM1 in the metastatic setting, including activity in CNS disease. These data provided a strong rationale to evaluate whether T-DXd could further improve outcomes in the curative-intent, postneoadjuvant setting.

Trial Design and Patient Population

DESTINY-Breast05 is a global, Phase III, open-label, randomized trial evaluating T-DXd versus T-DM1 in patients with HER2-positive early breast cancer and residual invasive disease following neoadjuvant therapy, enriched for high-risk features.

Eligible patients had:

  • Residual invasive disease in breast and/or axillary nodes
  • Either inoperable disease at presentation or node-positive disease after neoadjuvant therapy
  • Prior receipt of standard neoadjuvant systemic therapy, including taxane-based chemotherapy and HER2-targeted therapy

A total of 1635 patients were randomized 1:1 to:

  • T-DXd (5.4 mg/kg) every 3 weeks (N=818)
  • T-DM1 (3.6 mg/kg) every 3 weeks (N=817)
    for up to 14 cycles.

The Primary endpoint was invasive DFS, with key Secondary endpoints including DFS, distant recurrence, CNS outcomes, and Overall Survival (OS). Notably, this trial enrolled a higher-risk population than prior studies:

  • ~52% presented with inoperable disease at disease presentation
  • ~81% had node-positive disease after neoadjuvant therapy
  • ~79% received dual HER2 blockade preoperatively


Efficacy: A New Benchmark for Invasive Disease–Free Survival

At a median follow-up of approximately 30 months, T-DXd demonstrated a clinically and statistically significant improvement in outcomes compared with T-DM1:

    • IDFS events or death: 6.2% (T-DXd) vs. 12.5% (T-DM1); Hazard ratio (HR): 0.47 (P<0.001)
    • 3-year IDFS: 92.4% vs. 83.7%
    • 3-year DFS: 92.3% vs. 83.5% (HR: 0.47)

The benefit was consistent across prespecified subgroups, including hormone receptor–positive disease driven largely by a reduction in distant recurrences, the dominant mode of failure. Importantly, the distant recurrence: 5.1% vs. 9.9% and CNS recurrence was numerically lower with T-DXd (2.1% vs. 3.1%)

Although Overall Survival data remain immature, the magnitude of IDFS improvement strongly supports a meaningful long-term benefit.

Safety Profile: Balancing Efficacy with Toxicity

The safety profiles of both agents were consistent with prior experience, though distinct in nature. The common adverse events with T-DXd included nausea (71%), neutropenia, vomiting and alopecia. Approximately 50% of patients had grade ≥3 adverse events. T-DM1 was associated with hepatotoxicity (elevated transaminases) and thrombocytopenia.

Key Safety Signal: Interstitial Lung Disease (ILD)

The most clinically significant toxicity associated with T-DXd remains ILD. The incidence was 9.6% (T-DXd) vs. 1.6% (T-DM1). They were mostly grade 1–2, but grade ≥3 events occurred and two treatment-related deaths reported. The trial incorporated proactive ILD monitoring, including serial low-dose chest CT imaging, enabling early detection. Importantly no increased ILD risk was observed with concurrent radiotherapy. Multidisciplinary evaluation is critical to distinguish ILD from radiation pneumonitis.

Clinical Context: Positioning Within Current Practice

These findings represent a clear evolution beyond the KATHERINE standard, particularly in a more contemporary, higher-risk population treated with modern neoadjuvant regimens.

Implications for Clinical Practice

  • T-DXd emerges as the preferred postneoadjuvant therapy for patients with:
    • Residual invasive disease
    • Node-positive or otherwise high-risk features
  • T-DM1 remains relevant for:
    • Lower-risk residual disease
    • Patients unable to tolerate T-DXd

Evolving Treatment Paradigms and Open Questions

DESTINY-Breast05 raises several important considerations regarding treatment sequencing and personalization:

  1. Neoadjuvant Integration of T-DXd

Emerging data suggest that incorporating T-DXd earlier in the disease course may increase pCR rates and potentially reduce treatment duration. However, optimal sequencing remains undefined.

  1. Biomarker-Driven Personalization

Future strategies may incorporate circulating tumor DNA (ctDNA) clearance, HER2 expression heterogeneity and hormone receptor co-expression, to better tailor escalation vs. de-escalation approaches.

  1. CNS Disease Prevention

Although early signals suggest reduced CNS recurrence with T-DXd, longer follow-up is required to confirm whether this translates into durable CNS protection.

  1. Duration of Therapy

With a median of ~10 cycles delivered in this study, the optimal duration of T-DXd in the curative setting remains to be defined.


Limitations

  • Open-label design
  • Relatively short follow-up for survival endpoints
  • Underrepresentation of Black patients
  • Immature Overall Survival and CNS-specific outcomes

Conclusions

DESTINY-Breast05 establishes Trastuzumab deruxtecan as a new standard of care in the postneoadjuvant management of high-risk HER2-positive early breast cancer with residual disease. The trial demonstrates a substantial and clinically meaningful improvement in Invasive Disease–Free Survival, a reduction in distant recurrence and manageable but clinically significant toxicity, particularly interstitial lung disease.

As the field moves toward increasingly personalized, response-adapted strategies, T-DXd represents a major advance, while underscoring the need for vigilant toxicity monitoring and multidisciplinary care in the curative setting.

Trastuzumab Deruxtecan in Residual HER2-Positive Early Breast Cancer. Loibl S, Park YH, Shao Z, et al. for the DESTINY-Breast05 Trial Investigators. N Engl J Med 2026;394:845-857.

Reassessing the Role of Carboplatin in Neoadjuvant Therapy for HER2-Positive Breast Cancer: Insights from the neoCARHP Trial

RR

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

Human epidermal growth factor receptor 2–positive (HER2+) breast cancer accounts for approximately 15%–20% of all breast malignancies and historically has been associated with aggressive disease biology. Over the past decade, the integration of dual HER2 blockade with Trastuzumab (HERCEPTIN®) and Pertuzumab (PERJETA®) alongside cytotoxic chemotherapy has substantially improved outcomes. In patients with Stage II–III disease, neoadjuvant therapy has become the standard treatment approach, enabling early assessment of treatment response and guiding postoperative therapy.

The combination of a Taxane, Carboplatin, Trastuzumab, and Pertuzumab (TCbHP) is widely endorsed by treatment guidelines as a preferred neoadjuvant regimen. However, the inclusion of Carboplatin, originally incorporated as an anthracycline-sparing strategy to mitigate cardiotoxicity, remains a subject of ongoing debate. While platinum agents may enhance antitumor activity through DNA-damaging mechanisms and potential synergy with HER2-targeted therapy, Carboplatin is also associated with increased hematologic and gastrointestinal toxicities that frequently necessitate dose reductions or treatment interruptions.

Several earlier studies have questioned the incremental benefit of Carboplatin in HER2-positive disease. Trials in both metastatic and early-stage settings have suggested that the addition of platinum compounds may not significantly improve response outcomes, while contributing to higher rates of treatment-related toxicity. At the same time, multiple investigations evaluating chemotherapy de-escalation strategies have demonstrated promising activity with taxane-based regimens combined with dual HER2 blockade alone.

Against this evolving backdrop, the Phase III neoCARHP study sought to determine whether Carboplatin could be safely omitted from neoadjuvant therapy without compromising efficacy.

Study Design and Treatment Approach

The neoCARHP trial was a multicenter, open-label, randomized Phase III noninferiority study, conducted across 15 institutions. The study enrolled women aged 18 years or older with previously untreated Stage II or III HER2-positive invasive breast cancer. Patients with metastatic disease, inflammatory breast cancer, bilateral tumors, or prior systemic therapy for breast cancer were excluded.

Participants were randomly assigned in a 1:1 ratio to receive six cycles of either the standard TCbHP regimen or a Carboplatin-free regimen consisting of a Taxane plus Trastuzumab and Pertuzumab (THP). Taxane selection, including Docetaxel, Paclitaxel, or nab-Paclitaxel, was left to investigator discretion. Importantly, Docetaxel dosing differed between arms, with a higher dose used in the THP arm to maintain treatment intensity in the absence of Carboplatin.

All patients received Trastuzumab and Pertuzumab every three weeks. Surgery was scheduled within six weeks following completion of neoadjuvant therapy. Postoperative treatment followed standard guidelines: patients achieving a pathologic Complete Response (pCR) typically continued Trastuzumab with or without Pertuzumab to complete one year of HER2-targeted therapy, while those with residual disease were eligible to receive adjuvant Trastuzumab emtansine (KADCYLA®).

Between April 2021 and August 2024, 774 patients were randomized, and 766 who received at least one dose of study therapy were included in the efficacy analysis. Baseline characteristics were well balanced between the treatment arms, with most patients presenting with Stage II disease and approximately one-third being node-negative.

The Primary endpoint of the trial was the rate of pathologic Complete Response in the breast and axilla (ypT0/is ypN0) in the modified intention-to-treat population.

Efficacy Outcomes

Pathologic Complete Response was achieved in 64.1% of patients treated with the Carboplatin-free THP regimen compared with 65.9% in the TCbHP group. The absolute difference of –1.8% fell well within the prespecified noninferiority margin, confirming that THP was statistically noninferior to the standard Carboplatin-containing regimen.

Per-protocol analyses yielded nearly identical results, with both treatment groups demonstrating a pCR rate of 68.5%. Importantly, subgroup analyses showed consistent outcomes across clinically relevant populations, including both Hormone Receptor–positive and Hormone Receptor–negative disease. Among patients with Hormone Receptor–negative tumors, pCR rates approached 78% in both treatment arms.

Safety and Tolerability

A key finding of the neoCARHP study was the improved safety profile associated with the Carboplatin-free regimen. Grade 3 or 4 adverse events occurred in 20.7% of patients receiving THP compared with 34.6% in those treated with TCbHP. Serious adverse events were also less frequent in the THP arm (1.3% vs 4.7%).

Hematologic toxicities were notably reduced with Carboplatin omission. Rates of neutropenia and leukopenia were significantly lower in the THP group, and gastrointestinal toxicities such as diarrhea occurred less frequently. Overall toxicity rates were similar between groups, but the majority of events were low grade. No treatment-related deaths were reported.

These findings suggest that eliminating Carboplatin may substantially reduce treatment-related morbidity while preserving efficacy.

Clinical Context and Emerging Evidence

The results of neoCARHP align with a growing body of evidence supporting chemotherapy de-escalation strategies in HER2-positive breast cancer. Multiple prior trials, including NeoSphere, WSG-ADAPT, COMPASS-HER2-pCR, and DAPHNe, have demonstrated that taxane-based regimens combined with dual HER2 blockade can achieve high pCR rates, particularly in Hormone Receptor–negative tumors.

Collectively, these studies suggest that approximately half of patients with Stage II–III HER2-positive breast cancer may achieve pCR after four cycles of THP, with response rates exceeding 60% after six cycles. For patients with Hormone Receptor–negative disease, pCR rates may approach 80%. Importantly, omitting Carboplatin appears to improve tolerability without compromising early efficacy outcomes, raising the possibility that selected patients with low- or intermediate-risk disease may safely receive less intensive chemotherapy.

Future Directions and Biomarker-Guided Treatment

Despite these encouraging results, several important questions remain. Long-term outcomes, including Event-Free Survival, invasive Disease–Free Survival, and Overall Survival, are still maturing in the neoCARHP trial. Because pCR is not universally validated as a surrogate for survival across all breast cancer subtypes, extended follow-up will be critical to confirm the durability of these findings.

Advances in biomarker-driven treatment selection may also play a key role in refining neoadjuvant strategies. Emerging tools such as PET-guided response assessment, genomic assays like HER2DX, and intrinsic subtype classification may help identify patients most likely to benefit from treatment de-escalation while ensuring that higher-risk individuals continue to receive optimal therapy.

Meanwhile, antibody–drug conjugates are rapidly entering the early-stage setting and could further reshape treatment paradigms. Agents such as Trastuzumab deruxtecan (ENHERTU&reg;) are currently being investigated in neoadjuvant and adjuvant trials and may eventually offer additional Carboplatin-free therapeutic options.

Clinical Takeaway

The Phase III neoCARHP trial demonstrates that a neoadjuvant regimen consisting of a taxane combined with Trastuzumab and Pertuzumab achieves pathologic Complete Response rates comparable to the standard TCbHP regimen while significantly reducing high-grade toxicities.

These findings support the potential omission of Carboplatin in selected patients with Stage II–III HER2-positive breast cancer and represent another step toward individualized, toxicity-conscious treatment strategies in early HER2-positive disease.

Neoadjuvant Taxane Plus Trastuzumab and Pertuzumab With or Without Carboplatin in Human Epidermal Growth Factor Receptor 2–Positive Breast Cancer: The Randomized Noninferiority Phase III neoCARHP Trial. Gao H-F, Ye G-L, Lin Y, et al. J Clin Oncol. DOI: 10.1200/JCO-25-02176

Expanding Targeted First-Line Options in BRAF V600E–Mutant Metastatic Colorectal Cancer: Insights From the BREAKWATER Trial

RR

SUMMARY: Colorectal cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that approximately 158,850 new cases of CRC will be diagnosed in the United States in 2026 and about 55,230 patients will die of the disease. The lifetime risk of developing CRC is about 1 in 23.

Advanced colon cancer is often incurable and standard chemotherapy when combined with anti EGFR (Epidermal Growth Factor Receptor) targeted monoclonal antibodies such as Panitumumab (VECTIBIX®) and Cetuximab (ERBITUX®), as well as anti VEGF agent Bevacizumab (AVASTIN®), have demonstrated improvement in Progression Free Survival (PFS) and Overall Survival (OS). The benefit with anti EGFR agents however is only demonstrable in patients with metastatic CRC (mCRC) whose tumors do not harbor KRAS mutations in codons 12 and 13 of exon 2 (KRAS Wild Type). It is now also clear that even among the KRAS Wild Type patient group about 15-20% have other rare mutations such as NRAS and BRAF mutations, which confer resistance to anti EGFR agents. Patients with Stage IV colorectal cancer are now routinely analyzed for extended RAS and BRAF mutations. KRAS mutations are predictive of resistance to EGFR targeted therapy.

BRAF is a very important intermediary of the RAS-RAF-MEK-ERK pathway. The BRAF V600E mutations results in constitutive activation of the MAP kinase pathway. Inhibiting BRAF can transiently reduce MAP kinase signaling. However, this can result in feedback upregulation of EGFR signaling pathway, which can then reactivate the MAP kinase pathway. This aberrant signaling can be blocked by dual inhibition of both BRAF and EGFR. It should be noted that BRAF V600E-mutated CRC is inherently less sensitive to BRAF inhibition than Malignant Melanoma.

Encorafenib (BRAFTOVI®) is a BRAF inhibitor and has target binding characteristics that differ from other BRAF inhibitors such as Vemurafenib (ZELBORAF®) and Dabrafenib (TAFINLAR®), with a prolonged target dissociation half-life and higher potency.

Metastatic colorectal cancer (mCRC) harboring the BRAF V600E mutation represents a biologically aggressive subtype associated with poor prognosis, higher rate of peritoneal metastasis, and historically limited responsiveness to conventional chemotherapy. Approximately 8% to 12% of patients with mCRC carry this mutation, and outcomes with traditional first-line regimens have been suboptimal. Approximately 20% of the BRAF-mutated population in the metastatic setting has MSI-High tumors, but MSI-High status does not confer protection to this patient group. Historically, patients with these mutations experienced shorter survival when treated with chemotherapy with or without biologics such as Bevacizumab, compared to their BRAF wild-type counterparts. While the BEACON CRC trial established the Encorafenib plus Cetuximab (EC) doublet as standard in the previously treated setting, the optimal first-line strategy remained undefined.

The global Phase III BREAKWATER trial was designed to evaluate whether combining targeted agents with standard chemotherapy could improve outcomes for patients with previously untreated BRAF V600E–mutant mCRC. Earlier analyses from the study demonstrated that the combination of Encorafenib and Cetuximab with modified FOLFOX6 (mFOLFOX6) significantly improved Response Rates and Progression-Free Survival compared with chemotherapy with or without Bevacizumab. These findings ultimately led to accelerated FDA approval in December 2024 for the targeted triplet regimen in the first-line setting.

However, Oxaliplatin-based therapy is not suitable for all patients. Cumulative exposure to Oxaliplatin is frequently associated with peripheral neuropathy, prompting clinicians to consider Irinotecan-based regimens such as FOLFIRI as an alternative chemotherapy backbone in the first-line setting. It is estimated that 20% to 25% of patients with newly diagnosed BRAF V600E–mutant mCRC receive FOLFIRI as part of their initial treatment strategy. To address this clinical reality, investigators expanded the BREAKWATER trial to evaluate whether targeted therapy could also enhance outcomes when combined with Irinotecan-based chemotherapy.

Study Design and Patient Population

Cohort 3 of the BREAKWATER study specifically examined the combination of Encorafenib plus Cetuximab with FOLFIRI, compared with FOLFIRI with or without Bevacizumab, representing standard care in this setting. Eligible patients had previously untreated BRAF V600E–mutant mCRC, measurable disease according to RECIST 1.1 criteria, and an ECOG Performance Status of 0 or 1.

A total of 147 patients were randomized in a 1:1 ratio to receive either the targeted therapy combination plus FOLFIRI (N=73) or the control regimen (N=74). Baseline characteristics were balanced between treatment arms, with a median patient age of 62 years, 46% male, and 60% with ECOG performance status 0. The Primary endpoint was Objective Response Rate (ORR) as assessed by Blinded Independent Central Review, while Progression-Free Survival (PFS) served as the key Secondary endpoint. Additional endpoints included Overall Survival (OS), Duration of Response (DOR), Time To Response (TTR), and Safety.

Significant Improvement in Objective Response Rate

At the time of the March 1, 2025 data cutoff, the combination of Encorafenib, Cetuximab, and FOLFIRI demonstrated a clinically meaningful and statistically significant improvement in confirmed Objective Response Rate compared with the control regimen.

The confirmed ORR reached 64.4% with the targeted therapy combination, compared with 39.2% in the control arm, corresponding to an odds ratio of 2.76 (P=0.0011). Responses included Complete Responses in 4.1% of patients receiving the targeted regimen versus 1.4% in the control group, while Partial Responses occurred in 60.3% and 37.8% of patients, respectively.

Importantly, the responses observed with the targeted regimen were rapid and durable. The median time to response was similar between groups, occurring at approximately 6.9 weeks with Encorafenib plus Cetuximab and FOLFIRI and 7.1 weeks with the control regimen. Although the median Duration of Response had not yet been reached in either group, a greater proportion of patients receiving the targeted combination experienced sustained responses lasting at least six months (57.4% vs 34.5%). Responses lasting 12 months or longer were observed only in the experimental arm.

Clinical benefit with the targeted regimen was consistent across prespecified patient subgroups, further supporting the robustness of the treatment effect.

Early Signals for Survival Benefit

While Overall Survival data remain immature, early findings suggest a potential survival advantage with the targeted regimen. At the time of analysis, 15.1% of patients in the Encorafenib–Cetuximab–FOLFIRI group had died, compared with 27.0% in the control arm, translating to a hazard ratio of 0.49. Longer follow-up will be required to confirm the durability of this emerging survival signal.

Treatment exposure also favored the experimental arm. Nearly 70% of patients receiving the targeted regimen remained on treatment, compared with approximately one-third of patients in the control group, with a median treatment duration of 9.9 months versus 7.4 months, respectively.

Manageable Safety Profile

The safety profile of the triplet regimen was consistent with the known effects of each agent, and the addition of Encorafenib and Cetuximab did not substantially compromise treatment tolerability. The most frequently reported adverse events with the combination regimen included nausea, diarrhea, and vomiting. Serious treatment-emergent adverse events occurred in 39.4% of patients in the experimental arm vs 36.8% in the control arm. Importantly, the incorporation of targeted therapy did not lead to a meaningful increase in chemotherapy discontinuation, with FOLFIRI discontinuation rates of 9.9% in the experimental arm versus 8.8% in the control group. Investigators also reported no new safety signals, reinforcing the feasibility of combining targeted therapy with an Irinotecan-based chemotherapy backbone.

Clinical Implications

The results from BREAKWATER Cohort 3, build on the earlier success of Encorafenib and Cetuximab combined with Oxaliplatin-based chemotherapy, and provide important new insights for clinical practice. For patients who may not be optimal candidates for Oxaliplatin due to concerns such as cumulative neurotoxicity, the Encorafenib–Cetuximab–FOLFIRI regimen represents a compelling alternative.

Taken together, the findings support the growing role of targeted therapy- based combinations in the first-line treatment of BRAF V600E–mutant mCRC, offering both improved response rates and the potential for durable disease control.

Looking Ahead

The BREAKWATER trial remains ongoing, and continued follow-up will clarify the long-term durability of responses and the ultimate impact on Overall Survival. Nonetheless, the current analysis highlights the expanding therapeutic landscape for patients with this challenging molecular subtype of colorectal cancer.

If confirmed with longer follow-up, the combination of Encorafenib, Cetuximab, and FOLFIRI may emerge as another frontline standard-of-care option, providing clinicians with greater flexibility to tailor treatment strategies based on patient characteristics and toxicity considerations.

BREAKWATER: Primary analysis of first-line encorafenib + cetuximab + FOLFIRI in BRAF V600E-mutant metastatic colorectal cancer. Kopetz S, Wasan HS, Yoshino T, et al: 2026 ASCO GI Cancers Symposium. J Clin Oncol 44, 2026 (suppl 2; abstr 13)

FDA Approves First Line HERNEXEOS® for HER2-mutant Advanced NSCLC

RR

SUMMARY: The FDA on February 26, 2026, granted accelerated approval to Zongertinib (HERNEXEOS®), a kinase inhibitor, for an expanded indication for adults with unresectable or metastatic non-squamous Non-Small Cell Lung Cancer (NSCLC) whose tumors have HER2 (ERBB2) Tyrosine Kinase Domain (TKD) activating mutations, as detected by an FDA-authorized test.

The American Cancer Society estimates that for 2026, about 229,410 new cases of lung cancer will be diagnosed and 124,990 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Non-Small Cell Lung Cancer (NSCLC) accounts for approximately 85% of all lung cancers and Adenocarcinoma is now the most frequent histologic subtype of lung cancer.

The HER or erbB family of receptors consist of HER1, HER2, HER3 and HER4. HER2 is a Tyrosine Kinase Receptor expressed on the surface of several tumor types including Breast, Gastric, Lung and Colorectal cancers. It is a growth-promoting protein, and HER2 overexpression/HER2 gene amplification is often associated with aggressive disease and poor prognosis in certain tumor types.

HER2 mutations unlike HER2 overexpression and gene amplification are oncogenic drivers and are detected in 2 to 4% of NSCLCs. They are more often detected in younger, female and never-smokers, and almost exclusively in Adenocarcinomas. Next-generation sequencing is used to identify HER2 mutations. Majority of HER2 mutations (80-90%) occur in exon 20, as either a duplication or an insertion of 12 nucleotides, resulting in the addition of four amino acids (YVMA) at codon 775 in the kinase domain. This distinct molecular entity is characterized by specific pathological and clinical behavior. These acquired HER2 gene mutations have been independently associated with cancer cell growth, aggressive form of disease and poor prognosis, and with an increased incidence of brain metastases.

The FDA in 2022 granted accelerated approval to ENHERTU® (Trastuzumab deruxtecan), for adult patients with unresectable or metastatic NSCLC whose tumors have HER2 (ERBB2) mutations. This is the first drug approved for HER2-mutant NSCLC. Trastuzumab deruxtecan, however, can be associated with toxicities including Interstitial Lung Disease (ILD). Similarly, Pan-HER TKIs such as Poziotinib and Pyrotinib have shown limited efficacy and are frequently associated with EGFR-related adverse events, underscoring the urgent need for more targeted, better-tolerated therapies.

Zongertinib (HERNEXEOS®) is a novel, oral, irreversible Tyrosine Kinase Inhibitor designed to selectively target HER2 while sparing EGFR, thus minimizing common toxicities such as rash and diarrhea.

Beamion LUNG-1 is an ongoing Phase 1a/1b multicenter, multi-cohort trial, evaluating Zongertinib in  patients with HER2-altered advanced or metastatic solid tumors (Phase 1a) and those with HER2-mutant advanced or metastatic NSCLC across multiple clinically relevant patient cohorts (Phase 1b). In the Phase 1a dose-escalation trial, Zongertinib showed encouraging preliminary activity at the recommended expansion doses of 120 mg and 240 mg once daily, with a low incidence of Grade 3 or higher adverse events.

The Phase 1b portion is an ongoing study of Zongertinib in three key Cohorts (Cohort 1, 2 and 5) and three exploratory Cohorts (Cohorts 3, 4 and 6)

  • Cohort 1: Pretreated NSCLC patients with tumors harboring HER2 mutations in the TKD (Tyrosine Kinase Domain), the most common category of HER2 mutations encountered in the clinic.
  • Cohort 2: Treatment-naïve NSCLC with HER2 TKD mutation
  • Cohort 3: NSCLC patients whose tumor had HER2 mutations outside the TKD or HER2 TKD mutation-positive squamous NSCLC, pretreated
  • Cohort 4: NSCLC with active brain metastases with a HER2 TKD mutation
  • Cohort 5: NSCLC patients whose tumors had HER2 mutations within the TKD and had previously received HER2-directed ADCs, including Trastuzumab deruxtecan.
  • Cohort 6: NSCLC patients with HER2 TKD mutation and prior systemic treatment including HER2-directed ADCs.

(Some reports define Cohort 5 as the post-ADC cohort. However, clinical trial documentation indicates Cohort 6 specifically addresses the requirement for previous HER2-directed ADC treatment in specific phases of the study)

Cohorts 3, 4 and 6 are exploratory

Patients were initially treated at 120 mg or 240 mg daily and following interim analysis, 120 mg was selected as the optimal dose based on a favorable efficacy and safety balance.

The FDA in August 2025, granted accelerated approval to Zongertinib, for adults with unresectable or metastatic non-squamous Non-Small Cell Lung Cancer (NSCLC) whose tumors have HER2 (ERBB2) Tyrosine Kinase Domain (TKD) activating mutations and who have received prior systemic therapy. This was based on Objective Response Rate (ORR) and Duration of Response (DOR). This cohort study also suggested that Zongertinib may offer a viable treatment option even in patients who have progressed on ADCs or harbor atypical HER2 alterations.

The present accelerated approval was based on the efficacy of Zongertinib in unresectable or metastatic, non-squamous NSCLC with HER2 TKD mutation, who had not received systemic therapy for advanced disease (Cohort 2). The efficacy analysis included 72 patients (N=72) and the major efficacy outcome measures were Objective Response Rate (ORR) and Duration of Response (DOR) as determined by Blinded Independent Central Review (BICR)

The ORR was 76%, with Complete Response seen in 11% and Partial Response noted in 65% of patients. Sixty four percent (64%) of responders had a DOR of 6 months or more and 44% had a DOR of 12 months or more. The researchers added that the present efficacy reinforces the existing efficacy data for Zongertinib in previously treated NSCLC tumors with HER2  TKD activating mutations.

Safety and Tolerability

In a pooled safety population, which included 292 patients with HER2-mutant NSCLC, both treatment-naïve and previously treated, the most common adverse reactions were diarrhea (54%), rash (27%), hepatotoxicity (26%), fatigue (25%), nausea (23%), and musculoskeletal pain (21%), and upper respiratory tract infection (20%). No cases of drug-related interstitial lung disease were observed. The safety profile compares favorably with existing HER2-targeted agents, including Trastuzumab deruxtecan, which has reported interstitial lung disease rates of up to 26% in earlier trials.

Clinical Context and Future Directions

Compared with other HER2-targeted agents including Trastuzumab deruxtecan and investigational pan-HER TKIs, Zongertinib stands out as the first targeted therapy for treatment naïve patients with HER2-mutant advanced NSCLC, with its high response rates, durability, and manageable toxicity, and once daily oral administration. While cross-study comparisons have inherent limitations, these results support Zongertinib as a promising, HER2-selective oral agent for patients with HER2-mutant NSCLC. The ongoing Phase 3 Beamion LUNG-2 trial (NCT06151574) will further assess Zongertinib in the first-line setting, providing critical data on its role relative to current standard-of-care therapies.

Conclusion

Zongertinib has emerged as a strong candidate in the evolving landscape of HER2-mutant NSCLC. With high response rates, durable outcomes, and a favorable safety profile, it may soon offer oncologists a powerful new tool for treating this difficult-to-manage patient population.

https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-zongertinib-unresectable-or-metastatic-non-squamous-non-small-cell

 

Expert Perspectives on MRD Testing in Multiple Myeloma

RR

Learn how leading oncologists use MRD to inform treatment strategy and predict relapse risk

Written by: Dr. Gary Simmons & Dr. Kashif Ali
This educational opportunity is sponsored by Adaptive Biotechnologies

Measurable residual disease (MRD) testing has become a valuable tool across the multiple myeloma disease continuum, offering unprecedented insight into disease burden, treatment response, and relapse risk.  NCCN guidelines define MRD negativity as the absence of clonal plasma cells by next generation flow cytometry or next generation sequencing (NGS), at a sensitivity of at least 1 in 10-5 cells, and recommend assessing MRD status after induction, post-transplant, post-consolidation and during maintenance therapy.1  MRD results are shaping key decisions ranging from the role and timing of autologous stem cell transplant to strategies for monitoring and treatment adjustment.  Notably, MRD may be measured from bone marrow or peripheral blood, with data indicating that blood-based testing complements – but does not replace – bone marrow-based testing.2  In this dual-perspective Thought Leader Article, Dr. Gary Simmons (Virginia Oncology Associates) explores how MRD guides transplant decision-making, and Dr. Kashif Ali (Maryland Oncology Hematology) examines the value of blood-based MRD in monitoring response and predicting relapse in multiple myeloma.

The Role of MRD in Informing Autologous Stem Cell Transplant Decision-Making

Despite remarkable advances in multiple myeloma therapy, autologous stem cell transplant still plays a role in the treatment of many patients.  Traditionally, clinical decision-making around transplant was limited to weighing patient-specific factors such as age, comorbidities, and the limited methods that existed to gauge response to induction therapy.  MRD testing provides unprecedented, personalized insight into the induction response achieved by each patient, which directly influences the decision of whether to follow up with transplant.  MRD does not diminish the value of transplant but is rather a stratification tool to identify patients who would derive additional benefit from transplant, from those for which monitoring would suffice.  Several clinical trials including Determination, Perseus and GMMG-HD7 have demonstrated that transplant increases achievement and duration of MRD negativity.3,4,5 Thus, there is a bi-directional relationship in which MRD negativity supports the therapeutic value of transplant, and MRD results help to ensure that patients receive the minimal level of treatment required to achieve optimal outcomes.

In my practice, I evaluate MRD status alongside several variables including patient age, comorbidities, and standard- vs high-risk cytogenetics per the International Myeloma Working Group, when deciding on upfront vs deferred vs no transplant following induction therapy.  In many cases, patient-specific factors significantly influence the weight of MRD results in guiding transplant decision-making.  Notable among these is patient age.  I tend to recommend transplant in young patients, even those who are MRD negative, given data showing a substantially increased disease-free survival6 and improved clinical outcomes in younger fit patients.7  Conversely, there are populations in which MRD negativity would lead me to defer upfront transplant, especially in patients demanding a conservative approach, such as those greater than 75-years-old and/or those with significant comorbidities.  In these patients, MRD negativity often leads me to delay transplant, with the understanding that if/when the patient relapses, there are alternative treatment options to pursue, such as CAR T-cell therapy.  In general, I encourage most standard-risk myeloma patients that if they are MRD negative over the next 5 years, the disease-free is similar with or without transplant; that is encouraging to patients.

As myeloma testing and treatment options rapidly evolve, it’s increasingly important to stay abreast of the gold standard MRD testing options and latest clinical guidelines, to ensure optimal patient outcomes.  We’re always reviewing the options and the depth of MRD testing in our myeloma patients.  At this point, I tend to exclusively use the clonoSEQ assay, as it has a depth of 1×10-6 cells.  We know that depth of MRD and duration of MRD are related to improved clinical outcomes.  Therefore, despite the clinical trials using a MRD cutoff of 1×10-5 cells, we prefer the increased sensitivity offered by clonoSEQ of 1×10-6, for optimal assurance that negativity accurately identifies patients who are truly “MRD negative”.  While this piece is focused on the value of MRD in guiding transplant decisions, it’s worth nothing that assay depth and sensitivity also come to be very important post-stem cell transplant – as MRD negativity after a few years of maintenance can be used to determine if patients can stop maintenance therapy.  In the MASTER trial, MRD status and cytogenetics could predict risk of relapse in two years, highlighting the utility of MRD to help guide continuing maintenance or identify patients who may be able to stop.8 Altogether, these insights underscore how MRD drives personalized care from transplant decision-making to maintenance, ensuring optimal outcomes for patients with multiple myeloma.

The Role of Peripheral Blood-Based MRD Assessment in Monitoring Disease Response

While bone marrow evaluation remains the standard method for MRD assessment, peripheral blood-based MRD testing is an increasingly valuable approach for guiding treatment decisions and monitoring response in multiple myeloma.  MRD negativity by both peripheral blood and bone marrow is associated with an improved progression-free survival (PFS) compared to one modality alone, underscoring their complementary nature.2 Notably, peripheral blood MRD positivity has a 100% positive predictive value of bone marrow MRD positivity.10  Understandably, the negative predictive value of peripheral blood MRD is lower, demonstrating that peripheral blood MRD negativity does not exclude bone marrow disease.11 Therefore, in my practice, blood-based MRD positivity does not prompt confirmatory bone marrow testing, whereas blood-based MRD negativity should be confirmed by bone marrow biopsy, if the goal is to alter treatment.

Confidence in blood-based MRD results is influenced by several factors, including myeloma disease biology and timing.  Patients who present with circulating plasma cells at diagnosis have more aggressive disease and worse outcomes.12,13,14 In the post-transplant setting, studies have shown that patients negative for circulating DNA at three months post-transplant had significantly better PFS (84 vs 31 months) with a positive predictive value of 93.3%.15,16 Those who achieve a complete response will have no detectable plasma cells, as opposed to those who have a relapse, and blood-based MRD testing opens the door to uncover previously undetectable levels of circulating plasma cells.  There are also situations, such as patients with patchy bone marrow involvement or extramedullary disease17, in which MRD assessment of blood is more informative and bone marrow testing alone would be insufficient.18

Timing is another important consideration.  The concordance between bone marrow and blood-based MRD is lowest early after transplant and increases with time, suggesting enhanced reliability of peripheral blood MRD during maintenance.19 Peripheral blood MRD is well suited for longitudinal monitoring post-induction, post-transplant, and especially during maintenance in situations where repeated bone marrow biopsies would not be feasible.10,20 I routinely incorporate peripheral blood MRD testing at these timepoints and find it to be a less invasive alternative that enables more frequent assessment of patients who are reluctant to undergo repeat bone marrow biopsies.20,21 When the goal is to continue maintenance treatment, I utilize serial peripheral blood MRD testing and myeloma-related lab tests.  In these scenarios, I would only check a bone marrow biopsy if the goal were to discontinue or de-escalate treatment.  In the case of a blood-based MRD positivity, given the high concordance between peripheral blood and bone marrow, I would not mandate that an unwilling patient also undergo bone marrow-based MRD.  In my practice and outside of a clinical trial, most patients with blood-based MRD positivity, after hearing about data on concordance, decide not to undergo bone marrow confirmation although I do offer it to them.  Together, the expanding clinical utility of MRD assessment by blood and bone marrow underscores its value for guiding treatment decisions, monitoring response and prognosticating outcomes in multiple myeloma.

References:

  1. National Comprehensive Cancer Network. Multiple Myeloma. Updated 2025-11-26.
  2. Langerhorst P, Noori S, Zajec M, et al. Multiple Myeloma Minimal Residual Disease Detection: Targeted Mass Spectrometry in Blood vs Next-Generation Sequencing in Bone Marrow. Clinical Chemistry.  2021;67(12):1689-1698.  doi:10.1093/clinchem/hvab187.
  3. Richardson PG, Jacobus SJ, Weller EA, et al. Triplet Therapy, Transplantation, and Maintenance until Progression in Myeloma.  The New England Journal of Medicine.  2022;387(2):132–147. doi:10.1056/NEJMoa2204925.
  4. Sonneveld P, Dimopoulos MA, Boccadoro M, et al. Daratumumab, Bortezomib, Lenalidomide, and Dexamethasone for Multiple Myeloma. The New England Journal of Medicine.  2024;390(4):301-313.   doi:10.1056/NEJMoa2312054.
  5. Goldschmidt H, Bertch U, Pozek E, et al. Isatuximab, Lenalidomide, Bortezomib and Dexamethasone Induction Therapy for Transplant-Eligible Patients with Newly Diagnosed Multiple Myeloma: Final Progression-Free Survival Analysis of Part 1 of an Open-Label, Multicenter, Randomized, Phase 3 Trial (GMMG-HD7). Blood.  2024;144(Supplement 1): 769.  doi: https://doi.org/10.1182/blood-2024-193308.
  6. Ebraheem M, Kumar SK, Dispenzieri A, et al. Deepening Responses after Upfront Autologous Stem Cell Transplantation in Patients with Newly Diagnosed Multiple Myeloma in the Era of Novel Agent Induction Therapy. Transplant Cell Ther.  2022;28(11):760.e1-760.e5.  doi:10.1016/j.jtct.2022.07.030.
  7. Liu J, Yan W, Fan H, et al. Clinical Benefit of Autologous Stem Cell Transplantation for Patients with Multiple Myeloma Achieving Undetectable Minimal Residual Disease after Induction Treatment. Cancer Res Commun.  2023;3(9):1770-1780.  doi:10.1158/2767-9764.CRC-23-0185.
  8. Costa LJ, Chhabra S, Medvedova E, et al. Daratumumab, Carfilzomib, Lenalidomide, and Dexamethasone With Minimal Residual Disease Response-Adapted Therapy in Newly Diagnosed Multiple Myeloma. J Clin Oncol.  2022;40(25):2901-2912.  doi:10.1200/JCO.21.01935.
  9. Terpos E, Malandrakis P, Ntanasis-Stathopoulos I, et al. Sustained bone marrow and imaging MRD negativity for 3 years drives discontinuation of maintenance post-ASCT in myeloma. Blood.  2025;145(20):2353-2360.  doi:10.1182/blood.2024027686.
  10. Lasa M, Notarfranchi L, Agullo C, et al. Minimally Invasive Assessment of Peripheral Residual Disease During Maintenance or Observation in Transplant-Eligible Patients With Multiple Myeloma. J Clin Oncol.  2025;43(2):125-132.  doi:10.1200/JCO.24.00635.
  11. Chandhok NS, Sekeres MA. Measurable residual disease in hematologic malignancies: a biomarker in search of a standard. EClinicalMedicine.  2025;86:103348.  doi:10.1016/j.eclinm.2025.103348.
  12. Bertamini L, Oliva S, Rota-Scalabrini D, et al. High Levels of Circulating Tumor Plasma Cells as a Key Hallmark of Aggressive Disease in Transplant-Eligible Patients With Newly Diagnosed Multiple Myeloma. J Clin Oncol.  2022;40(27):3120-3131.  doi:10.1200/JCO.21.01393.
  13. Li Q, Ai L, Zuo L, et al. Circulating plasma cells as a predictive biomarker in Multiple myeloma: an updated systematic review and meta-analysis. Ann Med.  2024;56(1):2338604.  doi:10.1080/07853890.2024.2338604.
  14. Li J, Wang N, Tesfaluul N, Gao X, Liu S, Yue B. Prognostic value of circulating plasma cells in patients with multiple myeloma: A meta-analysis. PLoS One.  2017;12(7):e0181447.  doi:10.1371/journal.pone.0181447.
  15. Dhakal B, Sharma S, Balcioglu M, et al. Assessment of Molecular Residual Disease Using Circulating Tumor DNA to Identify Multiple Myeloma Patients at High Risk of Relapse. Frontiers in Oncology.  2022;12:786451.  doi:10.3389/fonc.2022.786451.
  16. Dhakal B, Sharma S, Shchegrova S, et al. Personalized, ctDNA analysis to detect minimal residual disease and identify patients at high risk of relapse with multiple myeloma. Journal of Clinical Oncology.  2021;39(Suppl 15):8029.  doi:10.1200/JCO.2021.39.15_suppl.8029.
  17. van de Donk NWCJ, Pawlyn C, Yong KL. Multiple myeloma. Lancet.  2021;397(10272):410-427.  doi:10.1016/S0140-6736(21)00135-5.
  18. Manasanch EE. What to do with minimal residual disease testing in myeloma. Hematology Am Soc Hematol Educ Program.  2019;2019(1):137-141.  doi:10.1182/hematology.2019000080.
  19. Kubicki T, Dytfeld D, Barnidge D, et al. Mass spectrometry-based assessment of M protein in peripheral blood during maintenance therapy in multiple myeloma. Blood.  2024;144(9):955-963.  doi:10.1182/blood.2024024041.
  20. Wijnands C, Noori S, Donk NWCJV, VanDuijn MM, Jacobs JFM. Advances in minimal residual disease monitoring in multiple myeloma. Crit Rev Clin Lab Sci.  2023;60(7):518-534.  doi:10.1080/10408363.2023.2209652.
  21. Kumar S, Paiva B, Anderson KC, et al. International Myeloma Working Group Consensus Criteria for Response and Minimal Residual Disease Assessment in Multiple Myeloma. Lancet Oncology.  2016;17(8):e328-e346.  doi:10.1016/S1470-2045(16)30206-6.

Redefining First-Line Maintenance in HR-Positive, HER2-Positive Metastatic Breast Cancer

RR

SUMMARY: Breast cancer is the most common cancer among women in the US and about 1 in 8 women (12%) will develop invasive breast cancer during their lifetime. It is estimated that in the US, approximately 321,910 new cases of female breast cancer will be diagnosed in 2026, and about 42,140 women will die of the disease, largely due to metastatic recurrence.

Breast cancer remains a biologically heterogeneous disease, with approximately 70% of tumors expressing estrogen receptors (ER) and/or progesterone receptors (PR). Among patients with metastatic disease, Hormone Receptor (HR)–positive, HER2-negative tumors represent the most common subtype. However, 15%–20% of primary breast cancers overexpress HER2, a historically aggressive phenotype. Notably, more than half of HER2-positive tumors also coexpress hormone receptors, creating a biologically distinct subgroup characterized by signaling interplay between the HER2 and estrogen receptor pathways.

For patients with HR-positive, HER2-positive metastatic breast cancer, the current first-line standard consists of induction chemotherapy combined with dual HER2 blockade (Trastuzumab-HERCEPTIN® and Pertuzumab-PERJETA®), followed by maintenance HER2-targeted therapy plus endocrine therapy. While this approach has significantly improved outcomes, resistance remains inevitable for most patients. Preclinical data have consistently demonstrated bidirectional crosstalk between HER2 and ER signaling, as well as persistent activation of the cyclin D1–CDK4/6 axis, which may drive resistance to both endocrine and HER2-directed therapies. These mechanistic insights provided the scientific rationale for evaluating triple pathway inhibition, simultaneous targeting of HER2, ER, and CDK4/6 in this population.

Biological Rationale for CDK4/6 Inhibition

Cyclin-Dependent Kinases 4 and 6 (CDK4/6) regulate orderly progression from the G1 to S phase of the cell cycle through phosphorylation of the retinoblastoma (RB) protein. Aberrant activation of this pathway is implicated in tumor proliferation and therapeutic resistance across multiple breast cancer subtypes, including HER2-positive disease.

Palbociclib (IBRANCE®), an oral selective CDK4/6 inhibitor, suppresses RB phosphorylation and arrests cell-cycle progression. Preclinical HER2-positive models have demonstrated that sustained cyclin D1–CDK4/6 activity contributes to resistance to HER2-targeted therapies, and dual inhibition of CDK4/6 and HER2 has shown synergistic antitumor effects. Early-phase clinical studies further suggested that combining CDK4/6 inhibition with HER2-directed and endocrine therapy was feasible and potentially additive in efficacy. These findings led to the Phase 3 PATINA trial.

The PATINA Trial: Study Design

PATINA was an open-label, randomized Phase 3 study evaluating whether adding Palbociclib to maintenance therapy could extend disease control in patients with HR-positive, HER2-positive metastatic breast cancer.

Eligibility and Treatment Approach

Patients were enrolled after completing 4 to 8 cycles of induction chemotherapy plus HER2-targeted therapy without disease progression. Key eligibility criteria included:

  • HR positivity (≥1% nuclear staining by IHC)
  • HER2 positivity (IHC 3+ or ISH amplification per ASCO/CAP guidelines)
  • No prior systemic therapy for metastatic disease beyond induction
  • A disease-free interval ≥6 months after prior adjuvant HER2 therapy

A total of 518 patients were randomized 1:1:

  • Palbociclib arm (n=261): Maintenance HER2-targeted therapy + endocrine therapy + Palbociclib (125 mg orally, 21 days on/7 days off; dose reductions permitted)
  • Standard arm (n=257): Maintenance HER2-targeted therapy + endocrine therapy

Baseline characteristics were balanced. The median age was 53.4 years; 99% were female; 61.8% were postmenopausal. Importantly, 54.4% had de novo metastatic disease. The Primary endpoint was investigator-assessed Progression-Free Survival (PFS). Secondary endpoints included Objective Response, clinical benefit, safety, and Overall Survival.

Efficacy Outcomes: A Meaningful Extension of Disease Control

At a median follow-up of 53.5 months, the addition of Palbociclib resulted in a statistically and clinically significant improvement in PFS. The median PFS was 44.3 months in the Palbociclib group and 29.1 months in the standard therapy group (HR=0.75; P=0.02). The estimated PFS rates favored the Palbociclib arm over standard therapy at all measured time points and was 84.9% versus 73.2% at 12 months, 65,2% versus 55.3% at 24 months, and 46.5% versus 38.3% at 48 months respectively.

The depth and durability of response were also enhanced:

  • Confirmed response rate: 32.9% vs. 24.8%
  • Complete response rate: 14.3% vs. 11.3%
  • Median duration of confirmed response: 44.9 vs. 30.8 months

Importantly, when the induction phase is included, total first-line disease control in the Palbociclib arm extended beyond four years. Early mortality was uncommon, with 6-month Overall Survival exceeding 99% in both groups, reflecting favorable biology among patients who completed induction therapy.

The control arm’s median PFS of 29 months exceeded initial projections, likely reflecting mandated endocrine therapy use and the exclusion of patients who progressed during induction, factors that enriched the study population for more favorable disease biology.

Safety Profile

The safety findings were consistent with known toxicities of Palbociclib and HER2-targeted therapies. Neutropenia was the predominant toxicity and febrile neutropenia was rare. Grade 3 and Grade 4 adverse events were 79.7% and 10% in the Palbociclib group versus 30.6% and 3.6% in the standard therapy group.

Clinical Implications

The PATINA trial supports a paradigm shift in the maintenance setting for HR-positive, HER2-positive metastatic breast cancer. By targeting HER2, Estrogen Receptor signaling, and CDK4/6-mediated cell-cycle progression concurrently, this strategy addresses key resistance mechanisms.

Achieving a median PFS exceeding 44 months represents a meaningful advance in a disease subtype historically associated with aggressive biology. While antibody–drug conjugates and other potent HER2-directed agents remain appropriate for selected high-risk patients, this chemotherapy-sparing maintenance intensification strategy provides durable disease control in a substantial proportion of patients.

The open-label design and limited racial diversity are important considerations. Additional analyses evaluating patient-reported outcomes, biomarker correlates, and central nervous system outcomes are ongoing and may further refine patient selection.

Conclusion

The addition of Palbociclib to maintenance anti-HER2 and endocrine therapy significantly prolongs Progression-Free Survival in patients with HR-positive, HER2-positive advanced breast cancer, albeit with increased, but manageable, hematologic toxicity. Triple pathway inhibition targeting HER2, estrogen receptor, and CDK4/6 signaling may now represent a compelling first-line maintenance strategy capable of extending disease control beyond four years in appropriately selected patients.

Palbociclib for Hormone-Receptor–Positive, HER2-Positive Advanced Breast Cancer. Metzger O, Mandrekar S, Goel S, et al. N Engl J Med 2026;394:451-462