[A Case of Conversion Surgery after Nivolumab Monotherapy as Third-Line Therapy for Advanced Gastric Cancer].

A 79-year-old man with unresectable advanced gastric cancer due to invasion to the pancreas and positive lavage cytology( T4b, N+, M1, CY1, cStage ⅣB; Japanese classification of gastric carcinoma, 15th edition)received standard chemotherapy, including 6 courses of S-1 plus cisplatin as first-line therapy and 2 courses of paclitaxel plus ramucirumab followed by 6 courses of paclitaxel monotherapy as second-line therapy. The primary lesion became PD with these treatments. Subsequently, nivolumab monotherapy was introduced as third-line therapy. After 9 courses, the primary tumor shrunk, and lavage cytology turned to negative on diagnostic laparoscopy. We judged that the tumor was resectable, and the patient underwent radical total gastrectomy and D2 lymphadenectomy as conversion surgery. The pathological stage was ypT3(SS), N0, M0, CY0, and the therapeutic effect was Grade 1b. R0 resection was accomplished. He has been alive without recurrence for 18 months after resection without adjuvant chemotherapy.