MisMatch Repair Deficiency and MicroSatellite Instability May Predict Perioperative Chemotherapy Benefit in Operable GastroEsophageal Cancers

SUMMARY: The American Cancer Society estimates that about 28,000 new cases of stomach cancer will be diagnosed in the United States for 2017 and about 10,960 people will die of this disease. It is a leading cause of cancer-related deaths in the world. Patients with operable Gastric or GastroEsophageal adenocarcinoma frequently receive perioperative or neoadjuvant chemotherapy prior to surgical resection, as this has been associated with a modest improvement in Overall Survival (OS), compared with surgery alone. However, approximately 50% of the patients undergoing surgical resection will die of recurrent disease. Further perioperative chemotherapy can be associated with significant toxicities. For patients with GastroEsophageal cancer receiving neoadjuvant treatment, there are presently no validated prognostic biomarkers, and patient selection is based on preoperative clinical staging.

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 (Micro Satellite Instability) is therefore a hallmark of defective/deficient DNA MisMatchRepair (MMR) system and occurs in 15% of all colorectal cancers. Defective MisMatchRepair can be a sporadic or heritable event. Approximately 65% of the MSI colon tumors are sporadic and when sporadic, the DNA MisMatchRepair gene is MLH1. Defective MisMatchRepair can also manifest as a germline mutation occurring in 1 of the 4 MisMatchRepair genes which include MLH1, MSH2, MSH6, PMS2. This produces Lynch Syndrome (Hereditary Nonpolyposis ColoRectal Carcinoma – HNPCC), an autosomal dominant disorder and is the most common form of hereditary colon cancer, accounting for 35% of the MSI colorectal cancers. MSI tumors tend to have better outcomes and this has been attributed to the abundance of Tumor Infiltrating Lymphocytes in these tumors, from increased immunogenicity. These tumors are susceptible to PD-1 blockade and respond to treatment with checkpoint inhibitors such as KEYTRUDA® (N Engl J Med 372:2509-2520, 2015). Other MSI-High and dMMR (MMR deficient) tumors include, Endometrial and GastroIntestinal tumors and to a lesser extent Breast, Prostate, Bladder and Thyroid tumors.

MSI (Micro Satellite Instability) 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 MisMatchRepair genes. MMR gene deficiency can be detected by ImmunoHistoChemistry (IHC). MLH1 gene is often lost in association with PMS2. Approximately 10-20% of Gastric cancers are MSI high or MMR Deficient. Several retrospective studies have suggested favorable outcomes in patients with Gastric cancer with high MSI tumors, although none of these studies had a control group.

In the MAGIC trial (The UK Medical Research Council Adjuvant Gastric Infusional Chemotherapy), which is an open-label, multicenter, phase III study, patients with resectable GastroEsophageal cancer were randomized to receive either 6 cycles of perioperative Epirubicin, Cisplatin, and Infusional 5-FU (3 cycles before and 3 cycles after resection) plus surgery, or undergo surgery alone. In this study, patients treated with perioperative chemotherapy had improved Overall Survival (OS) compared with patients treated with surgery alone (5-year OS 36% versus 23%; HR=0.75; P=0.009).

The authors in this study additionally evaluated patients with operable GastroEsophageal cancers with High MicroSatellite Instability (MSI-H) or MMR deficiency (dMMR), and compared their survival with patients who had MicroSatellite Stable (MSS) GastroEsophageal cancer, when these patients were treated with surgery alone or surgery plus perioperative chemotherapy. The authors thus assessed survival outcomes based on MSI/MMR deficiency. Of the 503 clinical trial participants, MSI results were available for 303 patients and both MSI and MMR results were available in 254 patients. Patients who had High MSI or MMR deficiency treated with surgery alone, had a median OS that was Not Reached (NR) compared with a median Overall Survival (OS) of 20.5 months, among those who had neither high MSI nor MMR deficiency (HR=0.42; P=0.09). In contrast, patients who had either a High MSI or MMR deficiency, treated with surgery plus perioperative chemotherapy had a median OS of 9.6 months compared with a median OS of 19.5 months, among those who had neither High MSI nor MMR deficiency (HR=2.18; P=0.03). The overall concordance rate between MSI-H and MMR deficient status was 97.6%.

Based on these findings the authors concluded that patients with operable GastroEsophageal cancer with High MicroSatellite Instability or MMR deficiency, did not benefit from perioperative chemotherapy and could be spared from the toxicities of chemotherapy. These patients may benefit from therapy with PD-1 inhibitors, although this will need to be further investigated. If independently validated, MSI or MMR deficiency, determined by preoperative biopsies, could be used to select patients for perioperative chemotherapy. Mismatch Repair Deficiency, Microsatellite Instability, and Survival. An Exploratory Analysis of the Medical Research Council Adjuvant Gastric Infusional Chemotherapy (MAGIC) Trial. Smyth EC, Wotherspoon A, Peckitt C, et al. JAMA Oncol. 2017;3:1197-1203.

KEYTRUDA® (Pembrolizumab)

The FDA on September 22, 2017 granted accelerated approval to KEYTRUDA® for patients with recurrent locally advanced or metastatic, Gastric or GastroEsophageal Junction adenocarcinoma, whose tumors express PD-L1, as determined by an FDA-approved test. KEYTRUDA® is a product of Merck & Co., Inc.

FDA Approves KEYTRUDA® for Advanced Gastric Cancer

SUMMARY: The FDA on September 22, 2017 granted accelerated approval to KEYTRUDA® (Pembrolizumab), for patients with recurrent locally advanced or metastatic, Gastric or GastroEsophageal junction adenocarcinoma, whose tumors express PD-L1, as determined by an FDA-approved test. Patients must have had disease progression on or after two or more prior systemic therapies, including Fluoropyrimidine and platinum-containing chemotherapy and, if appropriate, HER2/neu-targeted therapy. Cancers of the esophagus and stomach are among the most prevalent malignancies and are a major cause of cancer-related mortality. It is estimated that in 2016 GastroEsophageal Adenocarcinoma (GEA) accounted for 43,280 new cases in the United States. The incidence of these tumors has been on the rise in the past decade. Majority of the patients with GEA have advanced disease at the time of initial presentation and have limited therapeutic options with little or no chance for cure. Patients with localized disease (stage II and stage III) are often treated with multimodality therapy and 40% of the patients may survive for 5 years or more.

KEYTRUDA® 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. In previously reported Phase I study, KEYTRUDA® showed promising antitumor activity with manageable safety, in patients with previously treated advanced gastric cancer.

Based on these findings, the authors conducted a global, multicohort, Phase II study (KEYNOTE 059), in which patients with advanced gastric or gastroesophageal junction cancer received KEYTRUDA® 200 mg every 3 weeks for up to 2 years or until disease progression or unacceptable toxicity. Cohort 1 in this study enrolled 259 patients of whom 57% (N=148) had PD-L1 positive tumors and these tumors were either MicroSatellite Stable (MSS), or had undetermined MicroSatellite Instability (MSI) or MisMatch Repair (MMR) status. PD-L1 expression was evaluated by the PD-L1 IHC (22C3 antibody) and PD-L1 positivity was based on a Combined Positive Score (CPS) of 1 or more. CPS is determined by the number of PD-L1 staining cells (tumor cells, lymphocytes, macrophages) divided by total number of tumor cells evaluated, multiplied by 100. The median age was 62 years, 76% were men and over 50% of the patients received KEYTRUDA® as third line treatment or beyond. The median duration of follow up was 5.4 months. Primary end points included Objective Response Rate (ORR), safety, and tolerability.

In the group of patients with PD-L1 positive tumors, the ORR was 15.5% with 2% Complete Responses and 13.5% Partial Responses. Among the responding patients, the response duration ranged from 3-19 months, with 58% of the responding patients having response durations of 6 months or longer and 26% of the responding patients having response durations of 12 months or longer. In this cohort of 259 patients, 3% had tumors that were determined to be MSI-High. The ORR in this group was 57%, with response duration ranging from 5-14 months. In the PD-L1 negative patients however, the ORR was only 5.5%.

It was concluded that KEYTRUDA® demonstrated promising antitumor activity and durable responses in patients with advanced Gastric/GastroEsophageal Junction cancer, who had progressed on more than 2 lines of therapy, with higher Objective Response Rates noted in patients with PD-L1-positive tumors. KEYNOTE-059 cohort 1: Efficacy and safety of pembrolizumab (pembro) monotherapy in patients with previously treated advanced gastric cancer. Fuchs CS, Doi T, Jang RW-J, et al. J Clin Oncol. 2017;35 (suppl; abstr 4003).

Guideline for HER2 Testing in Gastroesophageal Adenocarcinoma

SUMMARY: It is estimated that in 2016 GastroEsophageal Adenocarcinoma (GEA) accounted for 43,280 new cases in the United States. Majority of the patients with GEA have advanced disease at the time of initial presentation and have limited therapeutic options with little or no chance for cure. Patients with localized disease (stage II and stage III) are often treated with multimodality therapy and 40% of the patients may survive for 5 years or more. Approximately 7-38% of GEAs have amplification and/or overexpression of HER2. HER2 (ERBB2) is a proto-oncogene located on the long arm of chromosome 17 (17q12) that encodes a tyrosine kinase receptor, which upon dimerization and phosphorylation, initiates signaling pathways, that lead to cell division, proliferation, differentiation and anti-apoptosis signaling.

GastroEsophageal junction tumors have a higher incidence of overexpression of HER2 compared to gastric cancers. In the stomach, overexpression of HER2 varies with histologic type (intestinal-type having greater expression than diffuse-type) and differentiation (well and moderately differentiated tumors having greater expression than poorly differentiated tumors). Further, the heterogeneity of immunostaining is greater in GEA and the complete membrane staining required for positivity in breast cancer, is not common in GEA. Due to the high heterogeneity of a gastric cancer, it is appropriate to evaluate HER2 expression on biopsy specimens, especially in unresectable cases and reevaluate it on resected specimens, when available.

The NCCN (National Comprehensive Cancer Network) Clinical Practice Guidelines in Oncology for Gastric Cancer and Esophageal and Esophagogastric Junction Cancers, recommend assessment of HER2 overexpression using ImmunoHistoChemistry and/or gene amplification using FISH (Fluorescence In Situ Hybridization or another in situ hybridization method, in tumor samples from patients, with unresectable, locally advanced, recurrent, or metastatic GEA, for whom HERCEPTIN® may be potentially beneficial. Testing for HER2 is primarily performed on Formalin-Fixed and Paraffin-Embedded biopsy or resection tumor tissue from the primary or metastatic site. There are important differences in HER2 expression, scoring, and outcomes in GEA compared to breast carcinoma, and the need for HER2 guidelines (that include critical clinical and laboratory considerations) was therefore recognized. The CAP, American Society for Clinical Pathology, and ASCO convened an international expert panel to systematically review published documents and to develop an evidence-based guideline, to establish recommendations for HER2 testing in GastroEsophageal Adenocarcinoma.

HERCEPTIN® (Trastuzumab) is humanized monoclonal antibody that targets HER2. HERCEPTIN® is effective only in cancers where HER2 is overexpressed. In a previously published randomized phase III trial, HERCEPTIN® in combination with chemotherapy was shown to significantly improve Overall Survival compared with chemotherapy alone, in patients with HER2 positive advanced GEA.

The following are the Guideline Summary from the College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology

Guideline Questions

• What is the optimal testing algorithm for the assessment of Human Epithelial Growth Factor 2 (HER2) status in patients with GastroEsophageal Adenocarcinoma (GEA)?

• What strategies can help ensure optimal performance, interpretation, and reporting of established assays in patients with GEA?

Target Population: Patients with GEA.

Target Audience: Medical and surgical oncologists; oncology nurses and physician assistants; pathologists; general practitioners; and patients.

Key Points and Recommendations for Clinicians

Recommendation 1.1

For patients with advanced GEA who are potential candidates for HER2-targeted therapy, the treating clinician should request HER2 testing on tumor tissue.

Recommendation 1.2

Treating clinicians or pathologists should request HER2 testing on tumor tissue in the biopsy or resection specimens (primary or metastasis) preferably before the initiation of HERCEPTIN® therapy if such specimens are available and adequate. HER2 testing on fine-needle aspiration specimens (cell blocks) is an acceptable alternative.

Recommendation 1.3

Treating clinicians should offer combination chemotherapy and HER2-targeted therapy as the initial treatment of appropriate patients with HER2-positive tumors who have advanced GEA

Key Points and Recommendations for Pathologists

Recommendation 2.1

Laboratories/pathologists must specify the antibodies and probes used for the test and ensure that assays are appropriately validated for HER2 ImmunoHistoChemistry (IHC) and in situ hybridization (ISH) on GEA specimens.

Recommendation 2.2

When GEA HER2 status is being evaluated, laboratories/pathologists should perform/order IHC testing first, followed by ISH (In Situ Hybridization) when the IHC result is 2+ (equivocal). Positive (3+) or negative (0 or 1+) HER2 IHC results do not require further ISH testing.

Recommendation 2.3

Pathologists should use the Ruschoff/Hofmann method in scoring HER2 IHC and ISH results for GEA.

Recommendation 2.4

Pathologists should select the tissue block with the areas of lowest grade tumor morphology in biopsy and resection specimens. More than one tissue block may be selected if different morphologic patterns are present.

Recommendation 2.5

Laboratories should report HER2 test results in GEA specimens in accordance with the College of American Pathologists biomarker Template for Reporting Results of HER2 (ERBB2) Biomarker Testing of Specimens From Patients With Adenocarcinoma of the Stomach or Esophagogastric Junction.

Recommendation 2.6

Pathologists should identify areas of invasive adenocarcinoma and also mark areas with strongest intensity of HER2 expression by IHC in GEA specimens for subsequent ISH scoring when required.

Recommendation 2.7

Laboratories must incorporate GEA HER2 testing methods into their overall laboratory quality improvement program, establishing appropriate quality improvement monitors as needed to ensure consistent performance in all steps of the testing and reporting process. In particular, laboratories performing GEA HER2 testing should participate in a formal proficiency testing program, if available, or an alternative proficiency assurance activity.

Recommendation 2.8

There is insufficient evidence to recommend for or against genomic testing in patients with GEA at this time.

HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma: Guideline Summary From the College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology. Bartley AN, Washington MK, Ismaila N, et al. Journal of Oncology Practice 2017;13:53-57.

CYRAMZA® (Ramucirumab)

The FDA on November 5, 2014 approved CYRAMZA® for use in combination with TAXOL® (Paclitaxel), for the treatment of patients with advanced Gastric or GastroEsophageal Junction (GEJ) adenocarcinoma. CYRAMZA® was approved in April, 2014 as a single agent for the treatment of patients with advanced Gastric or GEJ adenocarcinoma refractory to or progressive following first-line therapy with platinum or fluoropyrimidine chemotherapy. CYRAMZA® injection for intravenous infusion is a product of Eli Lilly and Company.

RAINBOW A global, phase III, randomized, double-blind study of ramucirumab plus paclitaxel versus placebo plus paclitaxel in the treatment of metastatic gastroesophageal junction (GEJ) and gastric adenocarcinoma following disease progression on first-line platinum- and fluoropyrimidine-containing combination therapy rainbow IMCL CP12-0922 (I4T-IE-JVBE)

SUMMARY: The FDA on November 5, 2014 approved CYRAMZA® (Ramucirumab) for use in combination with TAXOL® (Paclitaxel) for the treatment of patients with advanced gastric or GastroEsophageal Junction (GEJ) adenocarcinoma. CYRAMZA® was approved by the FDA in April, 2014 as a single agent for the treatment of patients with advanced gastric or GEJ adenocarcinoma, refractory to or progressive, following first-line therapy with platinum or fluoropyrimidine chemotherapy. It is estimated that there were approximately 21,600 new cases and 10,990 deaths from gastric cancer in the United States in 2013. The biology of gastric cancer appears to be different in different parts of the globe. Following progression after first line treatment for metastatic disease, the median survival is approximately 3 months. CYRAMZA® is a human IgG1 monoclonal antibody that inhibits VEGF-receptor 2, unlike AVASTIN® (Bevacizumab) which inhibits VEGF-A. The RAINBOW study is an international, placebo-controlled, double-blind, phase III trial in which 665 patients with metastatic gastroesophageal junction or gastric adenocarcinoma, who had disease progression on or within 4 months after first-line platinum and fluoropyrimidine-based combination therapy, were included. Patients were randomly assigned to receive TAXOL® (Paclitaxel) 80 mg/m2 given on D1, 8, 15 along with Placebo (N=335) or the same dose and schedule of TAXOL® given along with CYRAMZA® at 8 mg/kg IV every 2 weeks (N=330), of a 28 day cycle. Treatment was continued until disease progression or unacceptable toxicities were noted. The primary endpoint was Overall Survival (OS). Secondary endpoints included Progression Free Survival (PFS), Objective Response Rate (ORR) and Time To Progression (TTP). The median OS for the combination of CYRAMZA® and TAXOL® was 9.6 months compared to 7.4 months for Placebo and TAXOL® (HR=0.81; P=0.017), resulting in a 19% reduction in the risk of death with the CYRAMZA® and TAXOL® combination. The secondary endpoints favored the CYRAMZA® and TAXOL® combination as well. The median PFS was 4.4 months and 2.9 months (HR=0.64; P<0.001), ORR was 28% and 16% (P<0.0001) and median TTP was 5.5 months and 3 months with the CYRAMZA® and TAXOL® combination vs Placebo and TAXOL® combination respectively. As one would expect, treatment related adverse events were seen more frequently in the CYRAMZA® and TAXOL® combination group. Significant were neutropenia, hypertension, fatigue and asthenia, diarrhea and epistaxis. The incidence of febrile neutropenia in the two treatment groups was however comparable (3.1% vs 2.4%). The authors concluded that the combination of CYRAMZA® and TAXOL® combination significantly improved both Progression Free and Overall Survival and also resulted in significantly improved disease control rates, in patients with metastatic gastroesophageal junction or gastric adenocarcinoma. Wilke H, Van Cutsem E, Oh SC, et al. J Clin Oncol 32, 2014 (suppl 3; abstr LBA7)

CYRAMZA® Improves Overall Survival in Advanced Gastric Cancer

In a multinational double-blind phase III trial, targeting VEGFR-2 signaling with CYRAMZA® , improved overall survival in patients with previously treated advanced or metastatic gastric or gastroesophageal junction adenocarcinoma. CYRAMZA® is the first biological treatment that has demonstrated survival benefit when given as a single agent in this patient population. This study was published in the Lancet, 2014.

Ramucirumab monotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an international, randomised, multicentre, placebo-controlled, phase 3 trial

SUMMARY: It is estimated that there were approximately 21,600 new cases and 10,990 deaths from gastric cancer in the United States in 2013. The biology of gastric cancer appears to be different in different parts of the globe. Following progression after first line treatment for metastatic disease, the median survival is approximately 3 months. Ramucirumab (CYRAMZA®) is a recombinant human IgG1 monoclonal antibody that binds to Vascular Endothelial Growth Factor Receptor 2 (VEGFR-2) and blocks binding of the VEGFR ligands VEGF-A, VEGF-C, and VEGF-D and thus inhibits ligand-induced proliferation and migration of endothelial cells. This is unlike AVASTIN® (Bevacizumab) which inhibits VEGF-A. REGARD is a multinational double-blind phase III trial, in which 355 patients with previously treated advanced or metastatic gastric or gastroesophageal junction adenocarcinoma were randomly assigned in a 2:1 ratio to receive CYRAMZA® at 8 mg/kg, IV (N=238) or Placebo (N=117) every 2 weeks. Both groups also received best supportive care. The median age was 60 years and the ECOG performance of the patient population was 0 or 1. Patients received a median of four doses of CYRAMZA® or a median of three doses of Placebo. The primary endpoint was Overall Survival. The median Overall Survival in the CYRAMZA® group was 5.2 months vs 3.8 months in the Placebo group (HR = 0.78, P=0.047). The median Progression-Free Survival was also prolonged in the CYRAMZA® group (2.1 vs 1.3 months, HR = 0.48, P <0 .001). The most common adverse events of any grade in the CYRAMZA® group were hypertension, diarrhea, headache and hyponatremia. The authors concluded that VEGFR-2 signaling is an important therapeutic target in advanced gastric cancer and CYRAMZA® is the first biological treatment that has demonstrated survival benefit when given as a single agent in patients with advanced gastric or gastroesophageal junction adenocarcinoma, progressing after first-line chemotherapy. Fuchs CS, Tomasek J, Yong CJ, et al. Lancet. 2014;383:31-39

CYRAMZA® (Ramucirumab)

The FDA on April 21, 2014 approved CYRAMZA® for use as a single agent, for the treatment of patients with advanced or metastatic, gastric or gastroesophageal junction (GEJ) adenocarcinoma, with disease progression on or after prior treatment with fluoropyrimidine- or platinum-containing chemotherapy. CYRAMZA® injection for intravenous infusion is a product of Eli Lilly and Company.

RAINBOW A global, phase III, randomized, double-blind study of ramucirumab plus paclitaxel versus placebo plus paclitaxel in the treatment of metastatic gastroesophageal junction (GEJ) and gastric adenocarcinoma following disease progression on first-line platinum- and fluoropyrimidine-containing combination therapy rainbow IMCL CP12-0922 (I4T-IE-JVBE)

SUMMARY: It is estimated that there were approximately 21,600 new cases and 10,990 deaths from gastric cancer in the United States in 2013. The biology of gastric cancer appears to be different in different parts of the globe. Following progression after first line treatment for metastatic disease, the median survival is approximately 3 months. Ramucirumab is a human IgG1 monoclonal antibody that inhibits VEGF-receptor 2, unlike AVASTIN® (Bevacizumab) which inhibits VEGF-A. The RAINBOW study is an international, placebo-controlled, double-blind, phase III trial in which 665 patients with metastatic gastroesophageal junction or gastric adenocarcinoma, who had disease progression on or within 4 months after first-line platinum and fluoropyrimidine-based combination therapy, were included. Patients were randomly assigned to receive TAXOL® (Paclitaxel) 80 mg/m2 given on D1, 8, 15 along with Placebo (N=335) or the same dose and schedule of TAXOL® given along with Ramucirumab 8 mg/kg IV every 2 weeks (N=330), of a 28 day cycle. Treatment was continued until disease progression or unacceptable toxicities were noted. The primary endpoint was Overall Survival (OS). Secondary endpoints included Progression Free Survival (PFS), Objective Response Rate (ORR) and Time To Progression (TTP). The median OS for the combination of Ramucirumab and TAXOL® was 9.6 months compared to 7.4 months for Placebo and TAXOL® (P=0.016; HR=0.81), resulting in a 19% reduction in the risk of death with the Ramucirumab and TAXOL® combination. The secondary endpoints favored the Ramucirumab and TAXOL® combination as well. The median PFS was 4.4 months and 2.9 months (P<0.0001; HR=0.63), ORR was 28% and 16% (P<0.0001) and median TTP was 5.5 months and 3 months with the Ramucirumab and TAXOL® combination vs Placebo and TAXOL® combination respectively. As one would expect, treatment related adverse events were seen more frequently in the Ramucirumab and TAXOL® combination group. Significant were neutropenia, hypertension, fatigue and asthenia. The incidence of febrile neutropenia in the two treatment groups was however comparable (3.1% vs 2.4%). The authors concluded that the combination of Ramucirumab and TAXOL® significantly improved both progression-free and overall survival, with significantly improved disease control rates, in patients with metastatic gastroesophageal junction or gastric adenocarcinoma. Wilke H, Van Cutsem E, Oh SC, et al. J Clin Oncol 32, 2014 (suppl 3; abstr LBA7)