Successful Conversion Surgery Following Chylous Ascites After Nivolumab for Advanced Gastric Cancer

A 75-year-old man who underwent nivolumab as the third-line chemotherapy for advanced gastric cancer had chylous ascites (CA) after the primary tumor shrank remarkably. Total parenteral nutrition and subcutaneous octreotide were initiated, and CA disappeared. Nivolumab was continued for a total of 23 courses. Computed tomography showed lymph node swelling; however, staging laparoscopy showed that peritoneal metastasis had disappeared. Therefore, conversion surgery and distal gastrectomy with D1+ dissection were performed. The pathological diagnosis was type IV, poorly differentiated adenocarcinoma (por2) with signet ring cells, ypT2 (muscularis propria), without lymphatic or venous invasion, and no involvement of the proximal and distal margins. After the operation, no recurrence was observed over 7 months with no adjuvant chemotherapy. Nivolumab has the potential to lead to R0 resection for patients with peritoneal carcinomatosis gastric cancer. To our knowledge, this is the first report of successful conversion surgery after nivolumab-related chylous ascites.