Clinical and pathological disappearance of peritoneal dissemination in a patient with advanced gastric cancer receiving chemotherapy with S-1 and low-dose cisplatin.

A 54-year-old woman with severe abdominal distention suffered from massive ascites. Cytological examination revealed adenocarcinoma cells, leading to a diagnosis of peritonitis carcinomatosa. Gastrointestinal fiberscopy (GIF) resulted in a histological diagnosis of type 4 advanced gastric cancer with signet-ring cell carcinoma. The clinical diagnosis was confirmed to be cT3(SE)cN1cM0cH0cP1, cStage IV gastric cancer, type 4, according to the Japanese classification of gastric carcinoma. The patient was treated with S-1 and low-dose cisplatin (CDDP) in order to alleviate the critical state of the disease. After the third cycle of the regimen, the clinical response of P1 was classified as a partial response (PR) according to the World Health Organization (WHO) criteria. The patient's appetite loss and abdominal discomfort were markedly alleviated. The patient experienced grade 2 leukocytopenia throughout the regimen. Surgery was performed. Ascites and peritoneal disseminated lesions were not observed, and cytological examination of the peritoneal washes was negative. Total gastrectomy with D1 lymph node dissection was performed, and the surgical diagnosis was sT3(SE)sN0sM0sH0sP0; sStage II. Microscopically, viable cancer cells were found to be scattered throughout the subserosal-serosal layers in the resected stomach. All of the samples from lesions that were potentially cancers involving peritoneal dissemination were diagnosed as fibrous scar tissues without any viable cancer cells. The patient is alive without recurrence at 10 months after surgery and 14 months after the initial chemotherapy. Thus, systemic chemotherapy with S-1/low-dose CDDP achieved desirable control of peritoneal disseminated cells, as assessed microscopically, suggesting that the regimen may be an effective strategy for the treatment of advanced gastric cancer with peritonitis carcinomatosa.