[A Case of Unresectable Advanced Gastric Cancer with Peritoneal Metastases Radically Resected after Nivolumab...

A 75-year-old man presented with epigastric discomfort and weight loss and was diagnosed with unresectable advanced gastric cancer with small bowel and pancreatic invasion(cT4bN3aM0, CY0, P0, cStage ⅣA). He received standard chemotherapy, including 6 courses of S-1/oxaliplatin therapy as the first-line treatment and 2 courses of paclitaxel/ramucirumab therapy as the second-line treatment. Because of the primary tumor growth and appearance of massive ascites, nivolumab monotherapy was introduced as a third-line treatment. After 13 courses of nivolumab, the primary tumor significantly shrank, and the ascites disappeared. The patient underwent distal gastrectomy and D2 lymphadenectomy as conversion surgery. The pathological stage was ypT1aN0M0, CY0, P0, and ypStage ⅠA, and the therapeutic effect was Grade 2b. The patient was alive 42 months postoperatively with no evidence of recurrence. We report a case of a patient with unresectable gastric cancer with peritoneal metastases who underwent conversion surgery after a successful response to nivolumab therapy, with a limited literature review.