A case of successful S-1 alternate-day administration for far-advanced remnant gastric cancer

A 81-year-old man presented with anemia. He received a distal gastrectomy for gastric ulcer as a 40-year-old, and was also diagnosed with prostate cancer with bone metastasis as an 80-year-old. He has been undergoing treatment with anti-androgen therapy. Gastrointestinal endoscopic examination showed advanced gastric cancer, which was diagnosed as poorly differentiated adenocarcinoma. Computed tomography(CT)showed enlarged para-aortic lymph nodes. The clinical Stage was IV: cT3, N3, M1. He was treated with oral S-1 alternate-day administration of 100mg/day. The tumor in his remnant stomach shrunk in size by 3 months after beginning S-1 administration, and an endoscopic examination revealed a scar, but no cancer cells were found in a biopsy specimen of the scar tissue. Furthermore, CT scan showed that the swollen para-aortic lymph nodes were obviously reduced in size. As a result, we diagnosed this as a partial response to chemotherapy with S-1 alternate-day administration. No adverse events during the treatment were due to S-1 administration. His quality of life and poor food intake remarkably improved. S-1 alternate-day therapy demonstrated efficacy and tolerable toxicity even for a patient who was elderly and /or with poor performance status. S-1 can be managed safely on an outpatient basis without side effects for a long duration, and has been superior in terms of continuity of treatment.