Short- and long-term outcomes of neoadjuvant-synchronus S-1+radiotherapy for locally advanced rectal cancer: Multicenter phase II study.

Abstract

720 Background: Fluorouracil-based chemoradiotherapy (CRT) is regarded as a standard perioperative treatment in locally advanced rectal cancer. We investigated the efficacy and safety of substituting fluorouracil with the oral prodrug S-1. Methods: A multi-institutional (17 specialized centers), interventional phase II trial, was conducted from April 2009 to August 2011. For inclusion, patients must fulfill the following requirements before neoadjuvant CRT: (i) histologically proven rectal carcinoma; (ii) tumor located in the rectum (upper, lower); (iii) cancer classified as T3-4, N0–3 and M0; Two cycles of neoadjuvant CRT with S-1 (100 mg/m2 on days 1-5, 8-12, 22-26, and 29-33) was administered, and irradiation (total 45Gy/25fr, 1.8Gy/day, on days 1-5, 8-12, 15-19, 22-26, and 29-33) was performed. Total mesorectal excision was performed during the 4th and 8th week after the end of the neoadjuvant CRT. The primary endpoint is rate of complete treatment of neoadjuvant CRT. Secondary endpoints are response rate of neoadjuvant CRT, short-term clinical outcomes, rate of curative resection, and pathological response (grade2/3). Results: This trial included 37 patients (clinical StageIIA: 8, IIIB: 19, IIIC: 10; tumor located in the upper rectum; 4, the lower rectum; 33). A complete treatment of neoadjuvant CRT was found in 86.5% of patients (95%CI;75.5-97.5%), and an adverse event (grade 3/4) occurred in 4 patients(11.1%). Response rate (PR/CR;RECIST 1.0) was 56.8% (95%CI; 40.8-72.7%), and pathologic response rate (grade2/3) was 48.6% (95%CI; 32.5-64.8%). The median operating time was 448.5 min (IQR 340.5-505.5), and median blood loss was 422.5 mL (IQR 182.5-1125). Grade 3-4 postoperative complications occurred in 6 (16.7%) patients. The most common grade 3 or 4 postoperative complication was anastomotic leakage (2 [5.6%]). The 3-year overall survival rate was 88.5%. The 3-year disease free survival rate was 70.9%. Median length of follow-up was 42 months. Conclusions: A neoadjuvant-synchronus S-1+Radiotherapy for locally advanced rectal cancer is feasible in terms of pathological response, adverse events, accompany with favorable long-term outcome. Clinical trial information: 03396.