This study investigates treatment of durvalumab or placebo therapy combined with FLOT chemotherapy (flurouroacil + leucovorin + oxaliplatin + docetaxel) given before surgery (neoadjuvant) and durvalumab or placebo therapy combined with FLOT chemotherapy after surgery (adjuvant), will work and be safe for the treatment of resectable (removable by surgery) gastric or gastroesophageal cancer, and also to better understand the studied disease and associated health problems.
