Long-term outcomes of neoadjuvant-synchronous S-1 plus radiotherapy for locally advanced rectal cancer: a multi-institutional prospective phase II study

Objectives: This study aimed to evaluate the long-term outcomes of neoadjuvant chemoradiotherapy with S-1 in patients with locally advanced rectal cancer. Methods: A multi-institutional, prospective, phase II trial was conducted between April 2009 and August 2011. The study enrolled 37 patients with histologically proven rectal carcinoma (T3-4 N0-3 M0) who underwent neoadjuvant chemoradiotherapy with S-1. Total mesorectal excision with D3 lymphadenectomy was performed 4-8 weeks after completion of neoadjuvant chemoradiotherapy with S-1 in 36 patients. We then analyzed late adverse events, overall survival, and disease-free survival. Results: The median patient age was 59 years (range: 32-79 years); there were 24 men and 13 women. Ten patients had Stage II disease, and 27 had Stage III disease. Severe late adverse events occurred in 7 patients (18.9%). The 5-year disease-free survival was 66.7%, and the 5-year overall survival was 74.7%. The median follow-up period was 57 months. Local recurrences developed in 5 patients (13.5%), and distant metastases developed in 8 (21.6%). Conclusion: Neoadjuvant-synchronous chemoradiotherapy with S-1 for locally advanced rectal cancer is feasible in terms of adverse events and long-term outcomes. (UMIN Clinical Trial Registry: UMIN000003396)