Short- And Long-Term Outcomes Of Neoadjuvant-Synchronus S-1+Radiotherapy For Locally Advanced Rectal Cancer: Multicenter Phase Ii Study.

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 ...