Two cases of gastric cancer with peritoneal carcinomatosis successfully responding to combination chemotherapy of S-1 and cisplatin, leading to clinical complete response

We report two cases of gastric cancer with peritoneal carcinomatosis successfully responding to combination chemotherapy of S-1 and cisplatin, leading to a clinical complete response (cCR). In case 1, a 60-year-old woman achieved a cCR after 6 cycles of S-1 and cisplatin. Eight cycles of S-1 and cisplatin and 16 cycles of S-1 alone were administered. Since treatment with S-1 alone, only observation has been performed with no recurrence. In case 2, a 63-year-old man achieved cCR after 2 cycles of S-1 and cisplatin chemotherapy. After 8 cycles of chemotherapy, cCR was confirmed, and a curative operation was performed. After surgery, a small number of viable cells were found in the pathological examination. Fifty-four reports of cCR cases of advanced non-resectable or metastatic gastric cancer with chemotherapy have been published, but none mentioned the treatment options after cCR. In this report, we show two patients choosing different paths after achieving cCR by chemotherapy. In our surgical case, residues of pathologically viable cancer cells were confirmed, so surgery might be recommended after cCR, but further investigation will be needed.