A case of pathological complete response of advanced rectal cancer to preoperative chemoradiotherapy using S-1.

In patients with advanced rectal cancer, preoperative chemoradiotherapy is superior to postoperative chemoradiotherapy because of causing less toxicity and achieving higher rates of sphincter preservation and curative resection. We treated a patient who had advanced rectal cancer with preoperative chemotherapy using S-1 and concurrent radiotherapy. S-1 was orally administered at a dose of 100 mg/day during the first cycle (two-week on and one week off).