Phase I Study MK-3475 With Chemotherapy in Patients With Advanced GI Cancers

Inclusion Criteria: * Phase I: Patients with any locally advanced or metastatic gastrointestinal malignancy which mFOLFOX6 is indicated for treatment * Safety expansion: Patients with one of the following locally advanced unresectable or metastatic pathologically confirmed diagnosis: Colorectal Carcinoma and Appendiceal Adenocarcinoma, Gastro-Esophageal -Carcinoma Note: esophageal squamous cell carcinoma is exclusionary, Biliary -Tract Carcinoma Note: Hepatocellular carcinoma is excluded, Pancreatic Carcinoma * Patients must be willing to provide and have available formalin fixed paraffin embedded tissue sample from archival tissue or newly obtained core or excisional biopsy of a tumor lesion for central analysis. Note: Fine Needle Aspiration's (FNA), frozen samples, plastic embedded samples, cell blocks, clots, bone, bone marrow, or cytologic specimens are exclusionary * Patients must have measurable disease based on irRECIST (Safety expansion only) * Patients must be 18 years of age on day of signing informed consent * Have a performance status of 0 or 1 on the ECOG Performance Scale * Patients must demonstrate adequate organ function as based on screening labs performed within 14 days of treatment initiation * Patients are allowed to have received prior treatment with mFOLFOX6. If patients are currently receiving treatment with mFOLFOX6, the subject must have documented disease progression. Patients must also be able to tolerate standard mFOLFOX6. Reduced dosing of mFOLFO…