First Line KEYTRUDA® Superior to Chemotherapy in Metastatic MSI-H/dMMR Colorectal Cancer

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 147,950 new cases of CRC were diagnosed in the United States in 2020 and about 53,200 patients died of the disease. The lifetime risk of developing CRC is about 1 in 23. The majority of CRC cases (about 75 %) are sporadic whereas the remaining 25 % of the patients have family histories of the disease. Only 5-6 % of patients with CRC with a family history background are due to inherited mutations in major CRC genes, while the rest are the result of accumulation of both genetic mutations and epigenetic modifications of several genes. Colorectal Cancer is a heterogeneous disease classified by its genetics, and even though the diagnosis of Colorectal Cancer in the US is dropping among people 65 years and older, the incidence has been rising in the younger age groups, with 12% of Colorectal Cancer cases diagnosed in people under age 50.

The DNA MisMatchRepair (MMR) system is responsible for molecular surveillance and works as an editing tool that identifies errors within the microsatellite regions of DNA and removes them. Defective MMR system leads to MSI (Micro Satellite Instability) and hypermutation, with the expression of tumor-specific neoantigens at the surface of cancer cells, triggering an enhanced antitumor immune response. MSI is therefore a hallmark of defective/deficient DNA MisMatchRepair (dMMR) system and occurs in 15% of all colorectal cancers. Defective MMR can be a sporadic or heritable event. Approximately 65% of the MSI high colon tumors are sporadic and when sporadic, the DNA MMR gene is MLH1. Defective MMR can manifest as a germline mutation occurring in MMR genes including MLH1, MSH2, MSH6 and PMS2. This produces Lynch Syndrome often called Hereditary Nonpolyposis Colorectal Carcinoma – HNPCC, an Autosomal Dominant disorder that is often associated with a high risk for Colorectal and Endometrial carcinoma, as well as several other malignancies including Ovary, Stomach, Small bowel, Hepatobiliary tract, Brain and Skin. MSI is a hallmark of Lynch Syndrome-associated cancers. MSI high tumors tend to have better outcomes and this has been attributed to the abundance of tumor infiltrating lymphocytes in these tumors from increase immunogenicity. These tumors therefore are susceptible to blockade with immune checkpoint inhibitors.

MSI testing is performed using a PCR or NGS based assay and MSI-High refers to instability at 2 or more of the 5 mononucleotide repeat markers and MSI-Low refers to instability at 1 of the 5 markers. Patients are considered Micro Satellite Stable (MSS) if no instability occurs. MSI-L and MSS are grouped together because MSI-L tumors are uncommon and behave similar to MSS tumors. Tumors considered MSI-H have deficiency of one or more of the DNA MMR genes. MMR gene deficiency can be detected by ImmunoHistoChemistry (IHC). NCCN Guidelines recommend MMR or MSI testing for all patients with a history of Colon or Rectal cancer. Unlike Colorectal and Endometrial cancer, where MSI-H/dMMR testing is routinely undertaken, the characterization of Lynch Syndrome across heterogeneous MSI-H/dMMR tumors is unknown.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2, thereby undoing PD-1 pathway-mediated inhibition of the immune response and unleashing the tumor-specific effector T cells. The FDA in 2017 granted accelerated approval to KEYTRUDA® for patients with advanced MSI-High or dMMR solid tumors, that have progressed following prior treatment, and who have no satisfactory alternative treatment options. This has led to routine MSI-H/dMMR testing in advanced solid tumors.

KEYNOTE-177 is an International, multicenter, randomized open-label, Phase III trial conducted, to evaluate the efficacy and safety of KEYTRUDA® versus Standard-of-Care (SOC) chemotherapy, as first-line therapy for dMMR or MSI-H metastatic ColoRectal Cancer (mCRC). In this study, a total of 307 patients with MSI-H/dMMR mCRC as determined locally, and with ECOG PS of 0 or 1 were randomly assigned 1:1 to first-line treatment with KEYTRUDA® 200 mg IV every 3 weeks for up to 2 years (N=153) or investigator’s choice of mFOLFOX-6 or FOLFIRI every 2 weeks, with or without Bevacizumab or Cetuximab (N=154). Chemotherapy regimens were chosen prior to randomization. Treatment was continued until disease progression, unacceptable toxicity or completion of 35 cycles (for KEYTRUDA® only). The median patient age was 63 years and both treatment groups were well balanced. The co-Primary endpoints of the study were Progression Free Survival (PFS) and Overall Survival (OS). Key Secondary endpoints included Overall Response Rate (ORR) and Safety. Patients with confirmed disease progression on chemotherapy were given the option to crossover, to receive treatment with KEYTRUDA®.

At the second interim analysis, after a median follow up of 32.4 months, it was noted that KEYTRUDA® was superior to chemotherapy with a median PFS of 16.5 months versus 8.2 months for chemotherapy (HR=0.60; P=0.00002). The estimated restricted mean survival time after 24 months of follow up was 13.7 months in the KEYTRUDA® group as compared with 10.8 months in the chemotherapy group. Progression Free Survival was consistently longer with KEYTRUDA® than with chemotherapy across prespecified subgroups. The confirmed ORR was 43.8% with KEYTRUDA® versus 33.1% with chemotherapy, with Complete Responses in 11% and 4%, respectively. Among patients with an Overall Response, 83% in the KEYTRUDA® group had ongoing responses, as compared with 35% in the chemotherapy group at 24 months. The median Duration of Response was not reached in the KEYTRUDA® group and was 10.6 months in the chemotherapy group. Following disease progression, 36% of patients assigned to the chemotherapy group crossed over to the KEYTRUDA® group. This study is being continued to evaluate OS. Grade 3-5 treatment related Adverse Event rates were 22% in the KEYTRUDA® arm and 66% in the chemotherapy group.

The authors concluded that when compared to chemotherapy, first-line therapy with KEYTRUDA® provided a clinically meaningful and statistically significant improvement in Progression Free Survival, among patients with MSI-H/dMMR metastatic colorectal cancer, with fewer treatment-related Adverse Events. The authors added that KEYTRUDA® should be the new standard of care for this patient group.

Pembrolizumab in Microsatellite-Instability–High Advanced Colorectal Cancer. Andre T, Shiu K-K, Kim TW, et al. for the KEYNOTE-177 Investigators. N Engl J Med 2020;383:2207-2218.

First Line FOLFOXIRI Plus Bevacizumab May Be a Preferable Strategy for Metastatic Colorectal Cancer

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 147,950 new cases of CRC will be diagnosed in the United States in 2020 and about 53,200 patients are expected to die of the disease. The lifetime risk of developing CRC is about 1 in 23. Approximately 15-25% of the patients with CRC present with metastatic disease at the time of diagnosis (synchronous metastases) and 50-60% of the patients with CRC will develop metastatic disease during the course of their illness. Patients with metastatic CRC, whose disease has progressed after treatment with standard therapies, have limited therapeutic options available, to treat their disease.

In the TRIBE trial, the triplet combination FOLFOXIRI (Fluorouracil, Leucovorin, Oxaliplatin, and Irinotecan) plus Bevacizumab significantly improved Progression Free Survival compared with the doublet combination FOLFIRI (Fluorouracil, Leucovorin and Irinotecan) plus Bevacizumab in patients with metastatic colorectal cancer. However, the actual benefit of first line treatment with three cytotoxic drugs compared with a preplanned sequential strategy of using doublet therapy, as well as the feasibility or efficacy of these therapies after disease progression has remained unclear. The authors in this study aimed to compare a preplanned strategy of upfront FOLFOXIRI followed by the reintroduction of the same regimen after disease progression versus a sequence of mFOLFOX6 and FOLFIRI doublets, in combination with Bevacizumab. It should be noted that FOLFOXIRI regimen is not FOLFIRINOX. FOLFOXIRI regimen does not require a bolus infusion of Fluorouracil, involves a different infusional dose and schedule, and includes Irinotecan and Leucovorin at lower doses than does FOLFIRINOX.

TRIBE2 is an open-label, randomized, multicenter, Phase III study in which first line FOLFOXIRI followed by reintroduction of the same regimen after disease progression, was compared with a sequence of mFOLFOX6 (Fluorouracil, Leucovorin, and Oxaliplatin) and FOLFIRI (Fluorouracil, Leucovorin, and Irinotecan) doublets, in combination with Bevacizumab, in patients with unresectable, previously untreated metastatic colorectal cancer. A total of 679 patients were randomly assigned 1:1 to the control group (N=340) or experimental group (N=339). Patients in the control group received first-line mFOLFOX6 (Oxaliplatin 85 mg/m2 IV along with Leucovorin 200 mg/m2 IV over 120 min, Fluorouracil 400 mg/m2 IV bolus, followed by Fluorouracil 2400 mg/m2 continuous infusion over 48 hours) plus Bevacizumab 5 mg/kg IV over 30 min starting on day 1. Patients in the experimental group received FOLFOXIRI (Irinotecan 165 mg/m2 IV over 60 min, Oxaliplatin 85 mg/m2 IV along with Leucovorin 200 mg/m2 IV over 120 min, Fluorouracil 3200 mg/m2 continuous infusion over 48 hours) plus Bevacizumab 5 mg/kg IV over 30 min starting on day 1. Treatment was repeated every 14 days for up to 8 cycles. Patients then received maintenance treatment with Fluorouracil and Leucovorin along with Bevacizumab every 14 days until disease progression. After disease progression on maintenance treatment, patients in the control group received FOLFIRI (Irinotecan 180 mg/m2 IV along with Leucovorin 200 mg/m2 IV over 120 min, Fluorouracil 400 mg/m2 IV bolus, followed by Fluorouracil 2400 mg/m2 continuous infusion over 48 hours) plus Bevacizumab 5 mg/kg IV over 30 min starting on day 1 every 2 weeks for 8 cycles. This was followed by Fluorouracil and Leucovorin along with Bevacizumab maintenance. After disease progression on maintenance treatment in the experimental group, FOLFOXIRI was reintroduced for up to 8 cycles, followed by Fluorouracil and Leucovorin along with Bevacizumab maintenance. Patient demographics, clinical and molecular baseline characteristics, were well balanced in both treatment groups. The Primary endpoint was Progression Free Survival 2 (PFS2), defined as the time from randomization to disease progression on any treatment given after first disease progression.

At a median follow up of 35.9 months, the median PFS2 19.2 months in the experimental group versus 16.4 months in the control group (HR=0.74; P=0.0005). The median PFS1 was 12 months versus 9.8 months respectively (HR=0.74, P=0.0002). The Objective Response Rate (ORR) to first line treatment was 62% in the experimental group versus 50% in the control group (P=0.0023). The median Overall Survival was 27.4 months in the experimental group versus 22.5 months in the control group (HR=0.82; P=0.032). The most common Grade 3 or 4 adverse events during first-line treatment in the experimental group were diarrhea and neutropenia. Serious adverse events occurred in 25% of patients in the experimental group versus 17% of patients in the control group. After first disease progression, there were no significant differences in frequency of Grade 3 or 4 adverse events between the control and experimental groups, except for a higher incidence of neurotoxicity in the experimental group (5% versus 0%).

It was concluded that first line treatment with FOLFOXIRI plus Bevacizumab followed by the reintroduction of the same regimen after disease progression is the best first-line treatment option for select group of patients with metastatic colorectal cancer, compared to sequential administration of chemotherapy doublets, in combination with Bevacizumab.

Upfront FOLFOXIRI plus bevacizumab and reintroduction after progression versus mFOLFOX6 plus bevacizumab followed by FOLFIRI plus bevacizumab in the treatment of patients with metastatic colorectal cancer (TRIBE2): a multicentre, open-label, phase 3, randomised, controlled trial. Cremolini C, Antoniotti C, Rossini D, et al. Lancet Oncol 2020;21:497-505

Late Breaking Abstract – ASCO 2020: First Line KEYTRUDA® Superior to Chemotherapy in Metastatic MSI-H/dMMR Colorectal Cancer

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 147,950 new cases of CRC will be diagnosed in the United States in 2020 and about 53,200 patients are expected to die of the disease. The lifetime risk of developing CRC is about 1 in 23. The majority of CRC cases (about 75 %) are sporadic whereas the remaining 25 % of the patients have family histories of the disease. Only 5-6 % of patients with CRC with a family history background are due to inherited mutations in major CRC genes, while the rest are the result of accumulation of both genetic mutations and epigenetic modifications of several genes.Testing-for-MicroSatellite-Instability-and-MisMatch-Repair-Deficiency

The DNA MisMatchRepair (MMR) system is responsible for molecular surveillance and works as an editing tool that identifies errors within the microsatellite regions of DNA and removes them. Defective MMR system leads to MSI (Micro Satellite Instability) and hypermutation, triggering an enhanced antitumor immune response. MSI is therefore a hallmark of defective/deficient DNA MisMatchRepair (dMMR) system and occurs in 15% of all colorectal cancers. Defective MMR can be a sporadic or heritable event. Approximately 65% of the MSI colon tumors are sporadic and when sporadic, the DNA MMR gene is MLH1. Defective MMR can manifest as a germline mutation occurring in MMR genes including MLH1, MSH2, MSH6 and PMS2. This produces Lynch Syndrome often called Hereditary Nonpolyposis Colorectal Carcinoma – HNPCC, an Autosomal Dominant disorder that is often associated with a high risk for Colorectal and Endometrial carcinoma, as well as several other malignancies including Ovary, Stomach, Small bowel, Hepatobiliary tract, Brain and Skin. MSI is a hallmark of Lynch Syndrome-associated cancers. MSI tumors tend to have better outcomes and this has been attributed to the abundance of tumor infiltrating lymphocytes in these tumors from increase immunogenicity. These tumors therefore are susceptible to blockade with immune checkpoint inhibitors. MSI testing is performed using a PCR based assay and MSI-High refers to instability at 2 or more of the 5 mononucleotide repeat markers and MSI-Low refers to instability at 1 of the 5 markers. Patients are considered Micro Satellite Stable (MSS) if no instability occurs. MSI-L and MSS are grouped together because MSI-L tumors are uncommon and behave similar to MSS tumors. Tumors considered MSI-H have deficiency of one or more of the DNA MMR genes. MMR gene deficiency can be detected by ImmunoHistoChemistry (IHC). NCCN Guidelines recommend MMR or MSI testing for all patients with a history of Colon or Rectal cancer. Unlike Colorectal and Endometrial cancer, where MSI-H/dMMR testing is routinely undertaken, the characterization of Lynch Syndrome across heterogeneous MSI-H/dMMR tumors is unknown.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2, thereby undoing PD-1 pathway-mediated inhibition of the immune response and unleashing the tumor-specific effector T cells. The FDA in 2017 granted accelerated approval to KEYTRUDA® for patients with advanced MSI-High or dMMR solid tumors, that have progressed following prior treatment, and who have no satisfactory alternative treatment options. This has led to routine MSI-H/dMMR testing in advanced solid tumors.

KEYNOTE-177 is an International, multicenter, randomized open-label, Phase III trial conducted, to evaluate the efficacy and safety of KEYTRUDA® versus Standard-of-Care (SOC) chemotherapy, as first-line therapy for dMMR or MSI-H metastatic ColoRectal Cancer (mCRC). In this study, a total of 307 patients with MSI-H/dMMR mCRC as determined locally, and with ECOG PS of 0 or 1 were randomly assigned 1:1 to first-line treatment with KEYTRUDA® 200 mg IV every 3 weeks for up to 2 years (N=153) or investigator’s choice of mFOLFOX-6 or FOLFIRI every 2 weeks, with or without Bevacizumab or Cetuximab (N=154). Chemotherapy regimens were chosen prior to randomization. Treatment was continued until disease progression, unacceptable toxicity or completion of 35 cycles (for KEYTRUDA® only). The median patient age was 63 years and both treatment groups were well balanced. The co-Primary endpoints of the study were Progression Free Survival (PFS) and Overall Survival (OS). Key Secondary endpoints included Overall Response Rate (ORR) and Safety. Patients with confirmed disease progression on chemotherapy were given the option to crossover, to receive treatment with KEYTRUDA®. The median follow up was 28 months.

It was noted that KEYTRUDA® was superior to chemotherapy with a median PFS of 16.5 months versus 8.2 months for chemotherapy (HR=0.60; P=0.0002). The 12 and 24-months PFS rates were 55.3% and 48.3% with KEYTRUDA® versus 37.3% and 18.6% with chemotherapy, respectively. The confirmed ORR was 43.8% with KEYTRUDA® versus 33.1% with chemotherapy and the median Duration of Response was not reached in the KEYTRUDA® group and was 10.6 months in the chemotherapy group. Following disease progression, 36% of patients assigned to the chemotherapy group crossed over to the KEYTRUDA® group. This study is being continued to evaluate OS. Grade 3-5 treatment related Adverse Event rates were 22% in the KEYTRUDA® arm and 66% in the chemotherapy group.

The authors concluded that when compared to chemotherapy, first-line therapy with KEYTRUDA® provided a clinically meaningful and statistically significant improvement in Progression Free Survival, among patients with MSI-H/dMMR metastatic colorectal cancer, with fewer treatment-related Adverse Events. The authors added that KEYTRUDA® should be the new standard of care for this patient group.

Pembrolizumab versus chemotherapy for microsatellite instability-high/mismatch repair deficient metastatic colorectal cancer: The phase 3 KEYNOTE-177 study. Andre T, Shiu K-K, Kim TW, et al. J Clin Oncol 38: 2020 (suppl; abstr LBA4)

FDA Approves BRAFTOVI® in Combination with ERBITUX® for Metastatic Colorectal Cancer

SUMMARY: The FDA on April 8, 2020, approved BRAFTOVI® (Encorafenib) in combination with ERBITUX® (Cetuximab) for the treatment of adult patients with metastatic ColoRectal Cancer (CRC) with a BRAF V600E mutation, detected by an FDA-approved test, after prior therapy. Colorectal Cancer is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that approximately 147,950 new cases of CRC will be diagnosed in the United States in 2020 and about 53,200 patients are expected to 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 VECTIBIX® (Panitumumab) and ERBITUX® (Cetuximab) as well as anti VEGF agent AVASTIN® (Bevacizumab), 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. Approximately 8-15% of all metastatic CRC tumors present with BRAF V600E mutations and BRAF V600E is recognized as a marker of poor prognosis in this patient group. These patients tend to have aggressive disease with a higher rate of peritoneal metastasis and do not respond well to standard treatment intervention. 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.BRAF-and-MEK-Inhibition-in-MAPK-Pathway

The Mitogen-Activated Protein Kinase pathway (MAPK pathway) is an important signaling pathway which enables the cell to respond to external stimuli. This pathway plays a dual role, regulating cytokine production and participating in cytokine dependent signaling cascade. The MAPK pathway of interest is the RAS-RAF-MEK-ERK pathway. The RAF family of kinases includes ARAF, BRAF and CRAF signaling molecules. 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.

BRAFTOVI® (Encorafenib) is a BRAF inhibitor and has target binding characteristics that differ from other BRAF inhibitors such as ZELBORAF® (Vemurafenib) and TAFINLAR® (Dabrafenib), with a prolonged target dissociation half-life and higher potency. The combination of BRAFTOVI® along with anti-EGFR monoclonal antibody ERBITUX® (Cetuximab) showed promising activity in early-phase clinical trials.

The present FDA approval was based on BEACON CRC (Binimetinib, Encorafenib, and Cetuximab Combined to Treat BRAF-Mutant Colorectal Cancer) trial, which is an international, multicenter, randomized, open-label, Phase III study in which the efficacy and safety of BRAFTOVI® plus ERBITUX® with or without a MEK inhibitor MEKTOVI® (Binimetinib), was compared with the investigators’ choice of ERBITUX® combined with either Irinotecan or Fluorouracil, Folinic acid, and Irinotecan, in patients with BRAF V600E-mutant mCRC, whose disease has progressed after one or two prior regimens. Eligible patients were required to have BRAF V600E mutation-positive metastatic CRC (detected by the Qiagen therascreen® BRAF V600E RGQ PCR kit), with disease progression after one or two prior regimens. In this trial, 665 patients were randomly assigned in a 1:1:1 ratio to receive either triplet therapy of BRAFTOVI® 300 mg orally daily, MEKTOVI® 45 mg orally twice daily, and ERBITUX® 400 mg/m2 IV as an initial dose, then 250 mg/m2 IV weekly (N=224), doublet-therapy of BRAFTOVI® and ERBITUX® administered in the same doses and on the same schedule as the triplet regimen (N=220) or investigators’ choice of ERBITUX® combined with either Irinotecan or Fluorouracil, Folinic acid, and Irinotecan (N=221). Patients were stratified according to previous Irinotecan use and treatment was administered in 28-day cycles until disease progression. The co-Primary end points were Overall Survival (OS) in the triplet-therapy group as compared with the control group and Secondary end points included OS in the doublet-therapy group as compared with the control group, as well as Progression Free Survival, Duration of Response, and Safety in all groups. This study was not powered to compare the triplet-therapy group against the doublet-therapy group. The Overall Response Rate (ORR) and Duration of Response were assessed by blinded Independent Central Review in the subset of the first 220 patients assigned to receive either BRAFTOVI® and ERBITUX® or the control group.

The median OS was 8.4 months in the BRAFTOVI® plus ERBITUX® group, compared to 5.4 months in the control group (HR=0.60; P=0.0003), and this represented 40% reduction in the risk of death among the BRAFTOVI® plus ERBITUX® group. Median PFS was 4.2 months in the BRAFTOVI® plus ERBITUX® group compared to 1.5 months in the control group (HR=0.40; P< 0.0001). The ORR was 20% and 2% respectively. The median Duration of Response was 6.1 months for the BRAFTOVI® plus ERBITUX® group and Not Reached in the control arm. The median OS was 9.0 months in the triplet-therapy group and 5.4 months in the control group (HR for death=0.52; P<0.001). This represented 48% reduction in the risk of death in the triplet-therapy group. Both the triplet and doublet regimens reduced the risk of Quality of Life (QoL) deterioration by about 45% by different QoL assessment instruments, compared with the control regimen. The most common adverse reactions in the BRAFTOVI® plus ERBITUX® group were fatigue, nausea, diarrhea, dermatitis acneiform, abdominal pain, decreased appetite, arthralgia, and rash.

It was concluded from the BEACON CRC trial that a combination of BRAFTOVI®, MEKTOVI® and ERBITUX® as well as a combination of BRAFTOVI® plus ERBITUX® resulted in significantly longer Overall Survival and a higher Response Rate than standard therapy, in patients with metastatic Colorectal Cancer, with the BRAF V600E mutation.
Encorafenib, Binimetinib, and Cetuximab in BRAF V600E-Mutated Colorectal Cancer. Kopetz S, Grothey A, Yaeger R, et al. N Engl J Med 2019; 381:1632-1643

LONSURF® Plus AVASTIN® Combination for Chemo-Refractory Metastatic Colorectal Cancer 

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 147,950 new cases of CRC will be diagnosed in the United States in 2020 and about 53,200 patients are expected to die of the disease. The lifetime risk of developing CRC is about 1 in 23. Approximately 15-25% of the patients with CRC present with metastatic disease at the time of diagnosis (synchronous metastases) and 50-60% of the patients with CRC will develop metastatic disease during the course of their illness. Patients with metastatic CRC, whose disease has progressed after treatment with standard therapies, have limited therapeutic options available, to treat their disease.
LONSURF® is a combination of two agents – a novel oral nucleoside, Trifluridine and a thymidine phosphorylase inhibitor, Tipiracil hydrochloride. This combination has a unique mechanism of action. Trifluridine, the active ingredient of LONSURF® incorporates into DNA resulting in DNA damage. Degradation of Trifluridine which occurs when taken orally is prevented by Tipiracil hydrochloride. In a pivotal, global, Phase III trial (RECOURSE), LONSURF® significantly improved Overall Survival (OS) compared to placebo, with a 32% reduction in the risk of death, among patients with chemo-refractory metastatic CRC. AVASTIN® (Bevacizumab) is a humanized anti-VEGF monoclonal IgG1 antibody that directly binds Vascular Endothelial Growth Factor (VEGF) to inhibit angiogenesis.
In a previously published multicenter Phase I/II study (C-TASK FORCE), the combination of LONSURF® in combination with AVASTIN® showed promising antitumor activity with acceptable toxicity among patients with metastatic CRC. Based on the encouraging results of this study, the authors conducted an open-label, randomized, Phase II study in which the efficacy of LONSURF® plus AVASTIN® was compared with LONSURF® monotherapy in patients with refractory metastatic CRC. This study enrolled and randomly assigned 93 patients in 1:1 ratio to LONSURF® plus AVASTIN® (N=46) or LONSURF® alone (N=47). The main inclusion criteria were histopathologically confirmed metastatic CRC, refractory or intolerant to a Fluoropyrimidine (5-FU), Irinotecan (CAMPTOSAR®), Oxaliplatin (ELOXATIN®), and Cetuximab (ERBITUX®) or Panitumumab (VECTIBIX®), with the latter two agents offered only for RAS wild-type tumors. Patients had a WHO performance status of 0 or 1 and previous therapy with AVASTIN®, ZALTRAP® (Aflibercept), CYRAMZA® (Ramucirumab), or STIVARGA® (Regorafenib) was allowed. Randomized patients received LONSURF® 35 mg/m2 orally twice daily on days 1-5 and 8-12 every 28 days alone, or in combination with AVASTIN® 5 mg/kg IV on days 1 and 15 of each treatment cycle, until disease progression or unacceptable toxicity. Patients were stratified by institution and RAS mutation status. The Primary endpoint was Progression Free Survival (PFS).
After a median follow up of 10.0 months, the median PFS was 4.6 months in the LONSURF® plus AVASTIN® group versus 2.6 months in the LONSURF® monotherapy group (HR=0.45; P=0.0015). This represented a 55% reduction in the risk of progression or death. This benefit remained significant when analysis was adjusted for the stratification factors of study center and RAS mutation status (HR = 0.47, P =0.0015). The median Overall Survival was 9.4 months versus 6.7 months (HR=0.55, P =0.03) and Disease Control Rates were 67% versus 51% (P=0.14), in favor of the combination therapy. The most common treatment-related Grade 3 or more adverse events in the combination group were neutropenia and diarrhea.
It was concluded that among patients with chemo-refractory metastatic CRC, a combination of LONSURF® and AVASTIN® was associated with a significant and clinically relevant improvement in Progression Free Survival with tolerable toxicity, compared with LONSURF® monotherapy. The authors added that this could be a new treatment option and practice-changing development for patients with refractory metastatic CRC. TAS-102 with or without bevacizumab in patients with chemorefractory metastatic colorectal cancer: an investigator-initiated, open-label, randomised, phase 2 trial. Pfeiffer P, Yilmaz M, Möller S, et al. THE LANCET Oncology. Published:January 27, 2020DOI:https://doi.org/10.1016/S1470-2045(19)30827-7

Improved Quality of Life and Efficacy with BRAFTOVI®, MEKTOVI® and ERBITUX® Triplet Therapy in Patients with BRAF V600E-Mutant Metastatic Colorectal Cancer

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 147,950 new cases of CRC will be diagnosed in the United States in 2020 and about 53,200 patients are expected to 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 VECTIBIX® (Panitumumab) and ERBITUX® (Cetuximab), as well as anti VEGF agent AVASTIN® (Bevacizumab), 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. Approximately 5-20% of all metastatic CRC tumors present with BRAF V600E mutations and BRAF V600E is recognized as a marker of poor prognosis in this patient group. These patients tend to have aggressive disease with a higher rate of peritoneal metastasis and do not respond well to standard treatment intervention. 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.BRAF-and-MEK-Inhibition-in-MAPK-Pathway
The Mitogen-Activated Protein Kinase pathway (MAPK pathway) is an important signaling pathway which enables the cell to respond to external stimuli. This pathway plays a dual role, regulating cytokine production and participating in cytokine dependent signaling cascade. The MAPK pathway of interest is the RAS-RAF-MEK-ERK pathway. The RAF family of kinases includes ARAF, BRAF and CRAF signaling molecules. 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. However, BRAF V600E-mutated CRC is inherently less sensitive to BRAF inhibition than melanoma. BRAFTOVI® (Encorafenib) is a BRAF inhibitor and has target binding characteristics that differ from other BRAF inhibitors such as ZELBORAF® (Vemurafenib) and TAFINLAR® (Dabrafenib), with a prolonged target dissociation half-life and higher potency. The combination of BRAFTOVI® along with anti-EGFR monoclonal antibody ERBITUX® (Cetuximab) showed promising activity in early-phase clinical trials. 
The BEACON CRC (Binimetinib, Encorafenib, and Cetuximab Combined to Treat BRAF-Mutant Colorectal Cancer) trial is an international, multicenter, randomized, open-label, Phase III study in which the efficacy and safety of BRAFTOVI® plus ERBITUX® with or without a MEK inhibitor MEKTOVI® (Binimetinib), was compared with the investigators’ choice of ERBITUX® combined with either Irinotecan or Fluorouracil, Folinic acid, and Irinotecan, in patients with BRAF V600E-mutant mCRC, whose disease has progressed after one or two prior regimens. In this trial, 665 patients were randomly assigned in a 1:1:1 ratio to receive either triplet therapy of BRAFTOVI® 300 mg orally daily, MEKTOVI® 45 mg orally twice daily, and ERBITUX® 400 mg/m2 IV as an initial dose, then 250 mg/m2 IV weekly (N=224), doublet-therapy of BRAFTOVI® and ERBITUX® administered in the same doses and on the same schedule as the triplet regimen (N=220) or investigators’ choice of ERBITUX® combined with either Irinotecan or Fluorouracil, Folinic acid, and Irinotecan (N=221). Patients were stratified according to previous Irinotecan use and treatment was administered in 28-day cycles until disease progression. The co-Primary end points were Overall Survival (OS) in the triplet-therapy group as compared with the control group and Secondary end points included OS in the doublet-therapy group as compared with the control group, as well as PFS, Duration of Response, and Safety in all groups. This study was not powered to compare the triplet-therapy group against the doublet-therapy group.
At the time of prespecified interim analysis, with a median duration of follow up for survival at 7.8 months across the three groups, the median OS was 9.0 months in the triplet-therapy group and 5.4 months in the control group (HR for death=0.52; P<0.001). This represented 48% reduction in the risk of death in the triplet-therapy group. The confirmed Response Rate was 26% in the triplet-therapy group and 2% in the control group (P<0.001). The median OS in the doublet-therapy group was 8.4 months (HR for death versus control=0.60; P<0.001).
The authors in this updated analysis focused on the patient-reported Quality of Life (QOL) assessments from this study. QOL assessments using 4 validated QOL measures were secondary endpoints in the trial. They included EORTC QOL Questionnaire (QLQ C30), Functional Assessment of Cancer Therapy Colon Cancer (FACT C), EuroQol 5D 5L, and Patient Global Impression of Change (PGIC). The risk of QOL deterioration was reduced by 45% (HR=0.55) and 44% (HR=0.56), using EORTC QLQ C30 and FACT C assessments respectively, in favor of the triplet regimen over control. Similar findings were observed when the doublet-therapy regimen was compared with the regimen in the control group, and when QOL assessments were made using the other two QOL measures (EuroQol 5D 5L and PGIC). There was however no significant differences in QOL when the triplet and doublet regimen groups were compared.
It was concluded based on this updated analysis of the BEACON CRC trial, that among patients with BRAF V600E-mutant metastatic Colorectal Cancer, a combination of BRAFTOVI® plus ERBITUX® with or without a MEK inhibitor MEKTOVI®, demonstrated longer maintenance of QOL on patient-reported assessments, compared to the current standard of care. Encorafenib plus cetuximab with or without binimetinib for BRAF V600E-mutant metastatic colorectal cancer: Quality-of-life results from a randomized, three-arm, phase III study versus the choice of either irinotecan or FOLFIRI plus cetuximab (BEACON CRC). Kopetz S, Grothey A, Van Cutsem E, et al. J Clin Oncol. 2020;38(suppl 4; abstr 8).

Circulating Tumor DNA in the Peripheral Blood Predicts Recurrence Risk After Surgery and Adjuvant Chemotherapy in Stage III Colon Cancer

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 145,600 new cases of CRC were diagnosed in the United States in 2019 and about 51,020 patients died of the disease. The lifetime risk of developing CRC is about 1 in 23. Adjuvant chemotherapy for patients with resected, locally advanced, node-positive (Stage III) colon cancer has been the standard of care since the 1990s. Adjuvant treatment with an ELOXATIN® (Oxaliplatin) based chemotherapy regimen has been considered standard intervention since 2004, for patients with Stage III colon cancer, following surgical resection, and has been proven to decrease the chance of recurrent disease. Chemotherapy regimens have included (FOLFOX – Leucovorin, 5-FluoroUracil, ELOXATIN®) or CAPOX/XELOX (XELODA®/Capecitabine and ELOXATIN®), given over a period of 6 months. In spite of these advancements, defining patient subsets at high risk of recurrence following standard adjuvant therapy remains challenging and treatment failure can only be acknowledged when clinical recurrence is documented.
Cell-free DNA (cfDNA) refers to DNA molecules that circulate in the bloodstream after cell apoptosis or necrosis. A specific portion of cfDNA that originates from tumor cells is referred to as circulating tumor DNA (ctDNA), which can be detected in the cell-free component of peripheral blood samples in almost all patients with advanced solid tumors including advanced colorectal cancer. ctDNA is a valuable biomarker and allows early detection of relapse. Several studies have shown that detectable ctDNA following surgery for early stage cancers, is associated with a very high risk of recurrence. The authors in this publication report on the results of a correlative biomarker study in patients with Stage III colon cancer, undergoing standard adjuvant chemotherapy.
A multicenter, population-based, cohort study was conducted to determine whether serial post-surgical and post-chemotherapy ctDNA analysis could provide a real-time indication of efficacy of adjuvant therapy in Stage III colon cancer. In this study, 100 patients with newly diagnosed Stage III colon cancer who were planned to receive 24 weeks of adjuvant chemotherapy were enrolled. Patients had R0 resection with no evidence of metastatic disease on staging CT of the chest, abdomen, and pelvis before surgery. The chemotherapy regimen was chosen by the treating physician, who was blinded to the ctDNA result. High-risk patients were defined as those having pT4 and/or pN2 disease according to the pTNM staging system. Blood samples for ctDNA and CEA (CarcinoEmbryonic Antigen) analysis were collected 4-10 weeks after surgery prior to commencement of adjuvant chemotherapy and at the completion of adjuvant therapy, within 6 weeks of the final cycle of chemotherapy. All patients had a surveillance CT scan 4-8 weeks after completion of adjuvant chemotherapy. Follow up surveillance included clinical exam every 3 months along with CEA measurement and annual CT imaging for 3 years. Serial plasma samples were collected after surgery and after chemotherapy. Somatic mutations in individual patient tumors were identified by massively parallel sequencing of 15 genes commonly mutated in colorectal cancer, and personalized assays were designed to quantify ctDNA. For each patient, one mutation identified in the tumor tissue was assessed in the plasma for the presence of ctDNA. The median duration of follow up was 28.9 months and the primary aim of this study was to demonstrate the association between postsurgical and post-chemotherapy ctDNA detection and the risk of recurrence.
Among the 96 evaluable patients, circulating tumor DNA was detectable in 20 of 96 (21%) post-surgical samples and these patients had an increased risk of recurrence with associated inferior Recurrence-Free Survival, (HR=3.8; P<0.001). The estimated 3 year Recurrence Free Interval (RFI) for patients with positive ctDNA findings was 47% and for those with ctDNA-negative findings was 76%. Circulating tumor DNA was detectable in 15 of 88 (17%) post-chemotherapy samples. The estimated 3 year RFI was 30% when ctDNA was detectable after chemotherapy and 77% when ctDNA was undetectable (HR=6.8; P<0.001). Postsurgical ctDNA status was an independent predictor of disease recurrence after adjusting for known clinicopathologic risk factors (HR=7.5; P<0.001).
The authors concluded that post-surgical and post-chemotherapy circulating tumor DNA analyses is a promising prognostic marker in Stage III colon cancer, and may identify patients at high risk of recurrence, despite completing standard adjuvant treatment. This high-risk population presents a unique opportunity to explore additional therapeutic approaches. Circulating Tumor DNA Analyses as Markers of Recurrence Risk and Benefit of Adjuvant Therapy for Stage III Colon Cancer. Tie J, Cohen JD, Wang Y, et al. JAMA Oncol. 2019;5:1710-1717.

NCCN updates Colorectal Cancer Testing and Treatment Guidelines

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 145,600 new cases of CRC will be diagnosed in the United States in 2019 and about 51,020 patients are expected to die of the disease. The lifetime risk of developing CRC is about 1 in 23. Even though colon cancer localized to the bowel is potentially curable with surgery and adjuvant chemotherapy, advanced colon cancer is often incurable with a 5-year survival rate of 11%.

The 2019 NCCN guideline update for colon cancer has expanded the scope of personalized medicine and clinical diagnostics by incorporating biomarker testing to guide treatment. With the identification of new biomarkers and expansion of biomarker testing to guide treatment among patients with colorectal cancer, studies are underway to classify colorectal cancer (CRC) based on comprehensive gene expression profiles. The Consensus Molecular Subtypes (CMS) is one of the most robust transcriptome-based classification of colorectal cancer (CRC). The CMS subtype may influence the efficacy of chemotherapy and CMS might be a new predictive factor for the efficacy of chemotherapy against mCRCs. The CRC Subtyping Consortium (CRCSC) initiated by 15 institutions analyzed more than 30 different gene expression sets across multiple platforms and sample preparation methods and identified four different molecular subtypes, CMS1, CMS2, CMS3 and CMS4. This covers approximately 87% of all CRC cases, thus leaving approximately 13% of cases molecularly uncharacterized.

CMS1: Approximately 14 percent of all CRC are considered CMS1, of which approximately 12 percent are sporadic (non-inherited), while the remaining patients have inherited disease (Lynch Syndrome). Tumors are located in the proximal colon, have a high BRAF V600E mutation rate and are associated with impaired DNA mismatch repair (MMR). Patients in this group tend to have a lower rate of relapse and if relapse does occur, they are associated with poor outcomes (about 9 months). The 5-year survival rate for this group is about 73%.

CMS2: This is the most common CRC subtype with approximately 39% of the CRC patients belonging to this group. Majority of the tumors are located in the left colon and tumors are characterized by the initial loss of APC, a tumor suppressor gene, followed by an activating mutation in KRAS and loss of TP53. Patients in this group have higher survival rates (35 months) after relapse. The 5-year survival rate for this group is 77%, the best among the four different CRC subtypes.

CMS3: Approximately 13 percent of CRC patients belong to this group. KRAS mutations are most frequently found in this patient group (68%) and approximately 3% of patients in this group overexpress HER2. Patients in this group have the second highest survival rates, with a 5-year survival rate of 75%.

CMS4: These tumors are characterized by MSS (MicroSatellite Stable) with frequent mutation of genes such as APC, KRAS, PIK3CA, and TP53. Patients in this group often have poor prognosis as they are diagnosed at advanced stages. They have little or no benefit from systemic adjuvant therapy and those with metastatic disease are often resistant to EGFR inhibitors, independent of KRAS mutation status. They have the worst 5-year Overall Survival (62%) of any molecular subtype.

The following are the key 2019 NCCN guideline updates 

KRAS, NRAS and BRAF Mutation Testing

All patients with metastatic colorectal cancer should have tumor tissue genotyped for KRAS, NRAS and BRAF mutations individually or as a part of Next Generation Sequencing (NGS) panel

MicroSatellite Instability (MSI) or MisMatch Repair (MMR) Testing

1) The presence of BRAF V600E mutation in the setting of absence of MLH1 would preclude the diagnosis of Lynch Syndrome in a majority of cases. However, approximately 1% of cancers with BRAF V600E mutation and loss of MLH-1 are Lynch Syndrome and therefore, caution should be exercised, in excluding patients with a strong family history from germline screening in the case of BRAF V600E mutations

2) ImmunoHistoChemistry (IHC) refers to staining of tumor tissue for protein expression of the four mismatch repair MMR genes, MLH1, MSH2, MSH6, and PMS2, known to be mutated in Lynch Syndrome. A normal IHC test implies that all 4 MMR proteins are normally expressed or retained. An abnormal or positive IHC test implies loss or absence of expression of one or more of the 4 MMR proteins. When IHC is reported as positive, caution should be exercised to ensure that positive IHC refers to absence of mismatch expression and not presence of expression. Loss of expression by IHC in any of the MMR genes should then be followed up with genetic testing. Abnormal MLH1 on IHC should be followed by tumor testing for BRAF V600E mutation. The presence of BRAF V600 E mutation is consistent with sporadic cancer.

mFOLFOXIRI + EGFR

mFOLFOXIRI with EGFR inhibitor VECTIBIX® (Panitumumab) or ERBITUX® (Cetuximab) was added as a treatment option for unresectable stage IV mCRC that are left-sided and are KRAS/NRAS/BRAF wild-type.

mFOLFOX + EGFR

The combination regimen FOLFOX + VECTIBIX® or ERBITUX® was added for KRAS/NRAS/BRAF wild-type tumors.

Immunotherapy

Patients with advanced or metastatic CRC who are not appropriate candidates for intensive therapy may be offered OPDIVO® (Nivolumab) or KEYTRUDA® (Pembrolizumab), as a single agent or a combination of OPDIVO® and YERVOY® (Ipilimumab), only for tumors that are MMR deficient and MSI High (Category 2B). These same immunotherapy options are also listed in the guidelines as second and third-line options for MMR deficient and MSI High patients.

NTRK Gene Fusion

Tumors should be tested for Neurotrophic Receptor Tyrosine Kinase (NTRK) gene fusion, and VITRAKVI® (Larotrectinib) is now a second-line treatment option for patients with metastatic CRC that is NTRK gene fusion positive.

BRAF and MEK

BRAF wild-type was added as an indication for treatment, where KRAS and NRAS wild-type are noted. Combination therapies added to the guidelines as second-line options include

1) TAFINLAR® (Dabrafenib) targeting BRAF plus MEKINIST® (Trametinib) targeting MEK along with ERBITUX® or VECTIBIX® which are EGFR targeted monoclonal antibodies

2) BRAFTOVI® (Encorafenib) targeting BRAF plus MEKTOVI® (Binimetinib) targeting MEK along with ERBITUX® or VECTIBIX®.

NCCN Guidelines Updates: Management of Metastatic Colorectal Cancer. Messersmith WA. Presented at 2019 NCCN Annual Conference; March 21-23, 2019; Orlando, FL.