Impact of neoadjuvant chemotherapy following chemoradiation on tumor response, adverse events, and surgical complications in patients with advanced rectal cancer treated with TME.

3514 Background: A pathologic complete response (pCR) to pre-operative chemoradiation (CRT) is associated with improved prognosis in rectal cancer patients treated with total mesorectal excision (TME), but the proportion of patients who achieve a pCR is relatively small. We investigated the effect of adding increasing cycles of pre-operative neoadjuvant chemotherapy after CRT followed by surgery on pCR rate, adverse events (AEs) and surgical complications. Methods: Three sequential phase II trials or study groups (SGs) were conducted in patients with endorectal ultrasound or MRI Stage II and III rectal cancer. All patients were treated with neoadjuvant 5-FU-based CRT, followed by 0, 2 or 4 cycles of mFOLFOX-6 followed by TME. Tumor response was assessed by pathology according to RECIST criteria. AEs and surgical complications were reported according to CTCAE 3.0. Results: Demographics were similar between SGs. Clinical characteristics, treatment compliance, pathological tumor response, AEs and surgical co...