Abstract
528 Background: The standard treatment for locally advanced rectal cancer is neoadjuvant chemoradiation followed by surgery, but many physicians question the benefit of multimodality therapy in patients with stage T3N0M0 disease. We aimed to determine the impact of radiation therapy (RT) on overall survival (OS) in this group of patients. Methods: We used the Surveillance, Epidemiology, and End Results database to identify patients undergoing surgery for T3N0M0 adenocarcinoma of the rectum from 2004 to 2010. The Kaplan-Meier method was used to compare OS for patients receiving RT vs. no RT, along with for pre-op vs. post-op RT among patients that received RT. Multivariable analysis (MVA) using a Cox proportional hazards model was performed to assess the association of RT with OS after adjusting for patient age, gender, race, tumor grade, carcinoembryonic antigen, type of surgery, and circumferential margin status. The analysis was repeated separately on patients that underwent total colectomy (TC) vs. sphincter-sparing surgery. Results: The cohort included 8,679 patients, including 4,705 who received RT and 3,974 who did not. Median age was 66 years. Five year OS was 76.5% in patients who received RT, compared to 60.0% in patients who did not receive RT (p <0.001). Five year OS was 76.9% for patients receiving pre-op RT vs. 75.7% in patients receiving post-op RT (p = 0.247). In patients undergoing TC, five year OS was 74.7% for patients receiving RT, compared to 47.5% in patients not receiving RT (p <0.001). In patients undergoing sphincter-sparing surgery, five year OS was 77.7% in patients receiving RT, compared to 62.9% in patients not receiving RT (p <0.001). Use of RT was significantly associated with OS on MVA, both in the entire cohort (HR 0.70 [95% CI 0.60-0.81]; p<0.001) and in subsets of patients undergoing TC (HR 0.55 [95% CI 0.38-0.79]; p=0.001) and sphincter-sparing surgery (HR 0.70 [95% CI 0.59-0.84]; p<0.001). Conclusions: The use of RT is associated with superior OS in patients undergoing surgery for T3N0M0 adenocarcinoma of the rectum. This benefit is demonstrated in both the pre-op and post-op settings and applies to patients undergoing both TC and sphincter-sparing surgery.
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