A Study of Pembrolizumab With Trastuzumab and Chemotherapy in People With Esophagogastric Cancer

The purpose of this study to find out whether adding trastuzumab and pembrolizumab to standard chemotherapy is an effective treatment for resectable HER2+ esophagogastric cancer.

Inclusion Criteria: * Age 18 years or older at time of signing informed consent. * ECOG performance status 0-1. * HER2+ esophageal, GEJ, or gastric adenocarcinoma biopsy or resection specimen as defined by local HER2 IHC3+ or IHC 2+/FISH\>2.0 expression. * Complete surgical resection of the primary tumor must be achievable * Demonstrate adequate organ function as defined in Table 1. Table 1 - Organ Function Requirements for Eligibility Hematological * Absolute neutrophil count (ANC): ≥1,500 /mcL * Platelets: ≥100,000 / mcL * Hemoglobin: ≥8 g/dL Renal * Creatinine clearance: ≥ 50 mL/minute Hepatic * Serum total bilirubin: ≤ 1.5 X ULN OR Direct bilirubin ≤ ULN for subjects with total bilirubin levels \> 1.5 ULN. Except patients with Gilbert's disease (≤3x ULN) * AST and ALT: ≤ 2.5 X ULN * Albumin: \>3 mg/dL Coagulation * International normalized ratio (INR) OR prothrombin time (PT) Activated partial thromboplastin time (aPTT): \