[A Case of Stage Ⅳ Gastric Cancer with Distant Metastasis That Underwent Curative Surgery and Achieved Complete Response in Primary Lesion after Systemic Chemotherapy with Nivolumab].

We report a case of Stage Ⅳ gastric cancer, in case systemic chemotherapy with nivolumab was effective and curative resection was possible. A man in his 50s visited our hospital with complaints of general fatigue and anemia. Esophagogastroduodenoscopy revealed a type 3 tumor extending from the gastric cardia to angler incisure in the stomach. Abdominal contrast-enhanced computed tomography showed pancreatic invasion from the primary tumor and multiple lymph node metastases. Additionally, a single subcutaneous nodule around the umbilicus was detected. Staging laparoscopy showed P0, CY0. Excisional biopsy of subcutaneous nodule confirmed adenocarcinoma, diagnosing it as skin metastasis. The patient was diagnosed as advanced gastric cancer cT4bN3P0CY0M1(skin), cStage Ⅳ. Five courses of SOX with nivolumab therapy were administered. After 4 months, examinations showed clinical response in the primary lesion and lymph nodes. No new distant metastases were observed, and curative surgery was considered possible. Laparoscopic total gastrectomy with D2 lymphadenectomy, combined resection of distal pancreatectomy and spleen, Roux-en-Y reconstruction, was performed. Pathological examination revealed no residual cancer, indicating a histopathological evaluation of Grade 3. No complications were observed postoperatively and the patient was discharged on the 19th postoperative day. No recurrence was observed 6 months post-surgery. The administration of chemotherapy combined with immune checkpoint inhibitors for oligometastatic Stage Ⅳ gastric cancer was effective and resulted in curative surgery.