Racial and ethnic disparities in outcomes with radiation therapy for rectal adenocarcinoma

Race/ethnicity may modify cancer outcomes and manifest as survival disparities for patients with rectal cancer. Our objective was to determine whether disparate rectal cancer outcomes result from variable efficacy of radiation therapy for major racial/ethnic groups. The Los Angeles County Cancer Surveillance Program (CSP) identified patients with rectal adenocarcinoma between the years 1988 and 2006. Patients who underwent curative-intent surgery were grouped by race/ethnicity and by receipt (yes vs. no) and timing (neoadjuvant vs. adjuvant) of radiation therapy. The impact of receipt and timing of radiation therapy on overall survival was then assessed. Of 4,961 patients in CSP, 2,229 (45%) received radiation therapy. Overall, there was no difference in survival among patients according to receipt of radiation therapy. We then examined the radiation cohort, wherein 919 (41%) and 1,310 (59%) patients received neoadjuvant or adjuvant radiation, respectively. Overall, patients who received neoadjuvant compared to adjuvant radiation had improved survival (median survival (MS), 9.4 vs. 6.8 years, respectively; p < 0.001). Among those patients who received neoadjuvant radiation, whites, Hispanics, and Asians had significantly longer survival than blacks (MS, 10.4, 10.4, and 10.4 vs. 4.4 years, respectively; p = 0.003). On multivariate analysis, race/ethnicity was an independent predictor of survival (p = 0.001). To our knowledge, this is the first study examining the efficacy of radiation therapy for racial/ethnic groups with rectal cancer. Disparate outcomes were observed for the administration of radiation therapy for select racial/ethnic groups. The reasons for these disparities in outcomes should be investigated to better optimize radiation therapy for patients with rectal cancer.