Advanced Gastric Cancer with a Gastrocutaneous Fistula Confirmed as Showing Pathological Complete Response following Nivolumab Therapy and Conversion Surgery—Report of a Case of Long-term Survival—

Abstract

A 58-year-old woman underwent laparotomy for cT4aN1M0 gastric cancer. Due to invasion of the lesser curvature, including the hepatoduodenal ligament, and positive peritoneal lavage cytology, a gastrojejunostomy was performed. First-line SOX therapy was started, followed by second-line PTX+RAM therapy. The unresected tumor invaded the abdominal incision wound, resulting in the formation of a malignant gastrocutaneous fistula. Third-line nivolumab therapy was started immediately. This treatment showed a notable response, with the fistula closing completely after three courses. Finally, conversion surgery was performed after a total of 40 courses of nivolumab. The resected specimen showed no cancer cells and pCR in the primary tumor. Cancer cells were found to remain in only one lymph node, so she was finally diagnosed with ypT0N1 gastric cancer. Although no postoperative chemotherapy has been given, she has survived for five years without recurrence. It is extremely rare for gastric cancer to invade the abdominal wall skin and form a gastrocutaneous fistula, even in the wound following laparotomy. A case of a long-term survivor of advanced gastric cancer having a gastrocutaneous fistula confirmed as pCR following nivolumab therapy and conversion surgery is reported.