Phase II Study of Short Course FOLFOX Chemotherapy With Either Nivolumab or Nivolumab + Radiation in the First Line Treatment of Metastatic or Unresectable Gastroesophageal Cancers (BMS Protocol CA209-76L)

This is a randomized phase II study examining nivolumab alone versus radiation therapy with nivolumab in subjects who did not have disease progression to initial therapy with the combination of FOLFOX and Nivolumab. Subjects with advanced unresectable or metastatic gastroesophageal adenocarcinoma are eligible. All subjects will receive FOLFOX + nivolumab therapy. Subjects who demonstrate at least stable disease, as per RECIST 1.1, on their first imaging assessment at two months will receive one additional month of FOLFOX + nivolumab (3 months total), and then will be randomly assigned at a 1:1 ratio to receive either nivolumab alone or nivolumab plus radiation therapy. Radiation therapy fields and technique will be approved by central review. Radiation will be planned at 4Gy x 5 doses (20 Gy total), given concurrently with nivolumab. After 4 months of therapy, patients who remain on study will receive nivolumab 480 mg every 4 weeks. Subjects will be on study (intervention + follow‐up) for approximately 24 months. The projected end date of the study, including data analysis, is February 2026.