Objective: Obesity is a major health concern and risk factor for colorectal cancer that may also impact cancer treatment and outcomes. Rectal cancer response to chemoradiotherapy (CXRT) is associated with long-term survival and sphincter preservation. The purpose of this study was to evaluate the impact of obesity on treatment outcomes after neoadjuvant CXRT for rectal cancer.
Methods: A retrospective cohort study of patients diagnosed (1993 to 2010) with cT3-4 or cN+ (by endorectal ultrasound, computed tomography, or magnetic resonance imaging) rectal carcinoma and treated with CXRT and total mesorectal excision was performed. Patients were classified as obese (body mass index ≥30 kg/m) or nonobese (body mass index <30 kg/m), and by response to CXRT: complete (pCR) or incomplete (pIR). Associations between obesity, tumor response, and sphincter preservation were evaluated using multivariate logistic regression analysis and survival outcomes by Cox regression.
Results: A total of 753 patients met criteria and 28.7% (n=216) patients were obese. Obese and nonobese groups did not differ in age, sex, tumor location, grade, or number of examined lymph nodes. However, obesity was associated with a lower rate of pCR (ORmulti=0.60; 95% confidence interval, 0.38-0.94; P=0.04) and among mid to low rectal cancer patients, a lower rate of sphincter preservation (ORmulti=0.67; 95% confidence interval, 0.45-0.99). Among both obese and nonobese patients, CR was associated with more favorable recurrence-free survival than pIR.
Conclusions: Considering the increasing obesity prevalence and its association with CXRT response, oncologic outcomes, and sphincter preservation, further study is needed regarding the impact of obesity on neoadjuvant treatment response. Moreover, obesity should be targeted as a modifiable risk factor for adverse outcomes following multimodality treatment for rectal cancer.