Abstract
Gastric cancer is a leading global cause of cancer-related mortality. In the past, survival achieved in metastatic disease with chemotherapy was less than 1 year. The advent of immune checkpoint inhibitors has changed the treatment of gastric cancer. With demonstration of single agent activity for anti-programmed cell death protein 1 (anti-PD-1) agents in gastric cancer with a particularly high degree of activity in microsatellite instability (MSI) high cancers, global clinical trials added nivolumab and pembrolizumab to first line chemotherapy. Improvements in progression free survival, overall survival and increased response rates led to regulatory approval of these agents in the U.S. The benefit in survival seems limited, however, to patients with programmed cell death ligand 1 (PD-L1) positive or MSI high cancers. Adjuvant therapy with nivolumab improved disease-free survival after chemoradiotherapy and surgery in esophageal and gastroesophageal junction adenocarcinoma in patients with residual disease resected at surgery, and is a new care standard. Results of ongoing trials adding immune checkpoint inhibitors to perioperative chemotherapy in gastric cancer are anxiously awaited. In locally advanced MSI high gastric cancer, immune checkpoint inhibitor therapy is being explored as preoperative therapy given the demonstration of a high degree of pathologic complete response to these agents. Some trials may offer patients nonoperative management if a complete response is achieved.