The significance and long-term clinical outcome of preoperative chemoradiotherapy using S-1 plus Irinotecan for locally advanced rectal cancer.

Abstract

819 Background: Preoperative chemoradiotherapy regimen using S-1 plus Irinotecan is still under clinical investigation. The aim of this study was to investigate the significance and the long-term outcomes of this regimen for locally advanced rectal cancer. Methods: Between 2009 and 2016, 81 patients underwent radical surgery after preoperative chemoradiotherapy. Radiotherapy was administered in total 45Gy with 1.8Gy/day for 25 days. S-1 was administered orally in a fixed daily dose of 80mg/m2 on days 1 to 5, 8 to 12, 22 to 26, and 29 to 33. Irinotecan was infused with dose of 80 mg/m2 on days 1, 8, 22, and 29. 6-9 weeks after the completion of the treatment, radical surgery was performed. The median follow-up was 35.3 months. Results: Of the 81 patients, 76 (93.8%) completed treatment of chemoradiotherapy. Relative dose intensity of CPT-11 was 92.8%, S-1 was 90.1%. 79 (97.5%) patients completed the radiotherapy. 18 patients (22.2%) had ≧Grade 3 hematologic toxicity (leukopenia; 15 patients, neutropenia; 16 patients ). 23 patients (28.3%) had ≧Grade 3 nonhematologic toxicity (diarrhea). In terms of the surgical procedure, 73 of 81 patients (90.1%) underwent sphincter-preserving surgery including 42 patients intersphincteric resection, and 8 patients (9.9%) underwent abdominoperineal resection. The tumor regression grade of 1/2/3(pCR) was 30/39/12(14.8%). In terms of long-term survival, 3-year local relapse-free survival rate was 96.7%, the recurrence-free survival rate was 71.6% and 3-year overall survival rate was 94.9%. Conclusions: Preoperative chemoradiotherapy using combined with Irinotecan as secondary drugs may result safe and feasible and accomplished favorable downstaging. This regimen was considered to be effective in patients with locally advanced rectal cancer.