[A case report of pathologically complete response of rectal cancer after preoperative treatment of CPT-11, S-1, and radiation therapy].

A 52-year-old woman diagnosed with lower rectal cancer was referred to our hospital for the operation of anal sphincter preservation. Rectal examination and colonoscopy showed a type 2 semicircular tumor on the posterior wall at 4 .5-7 cm from anal verge with incomplete mobility (cT3). She was diagnosed as the moderately differentiated tubular adenocarcinoma by biopsy. Computed tomography and magnetic resonance imaging showed no sign of invasion to the surrounding organs and metastasis to lymph nodes or the other organs (cN0, cM0). We performed a preoperative chemoradiotherapy (CRT) combined with S-1 and CPT-11. Radiation (1.8 Gy) was administered a total of 45 Gy( day 1-5, 8-12, 15-19, 22-26, 29-33). S-1 was taken orally( 100 mg/day: day 1-5, 8-12, 22-26, 29-33), and CPT-11 was administered intravenously (60 mg/m²: day 1, 8, 22, 29). Endoscopy after CRT showed a reduction of the tumor size (from semicircular to quarter-circular) and lowering of marginal wall. Rectal examination revealed an improvement of tumor mobility. Eight weeks after CRT, the patient underwent ISR with partial ESR and covering ileostomy pathological examination demonstrated no residual cancer cell in the primary lesion and lymph node (Grade 3, pCR). Preoperative CRT can be a promising tool for locally advanced rectal cancer.