[A Case of Conversion Surgery after SOX plus Nivolumab for Unresectable Advanced Gastric Cancer].

A 63-year-old woman came to our hospital complaining of anemia and weight loss. The abdominal CT showed wall thickening from the upper to lower the body of stomach, and peritoneal dissemination. The EGD revealed a type 3 large tumor extending about 2/3 of the circumference. Adenocarcinoma was detected as a result of biopsy. The patient was diagnosed with unresected gastric cancer(cT4aN+M1, cStage Ⅳ). SOX plus nivolumab was selected as a first-line chemotherapy because of HER2 expression negative. Symptoms such as diarrhea developed, and the treatment was completed until 5 courses. Laparoscopic distal gastrectomy was performed after the disappearance of abdominal dissemination by CT scan and PET. Pathological examination revealed cancer cells were completely disappeared in the tumor, regional lymph nodes and white nodules in the peritoneum, and final diagnosis was ypT0N0M0, ypStage 0(histological effect determination is Grade 3). Six months after the operation, the patient has been free of recurrence.