Abstract B80: Timing of radiation therapy for rectal cancer improves survival for select racial/ethnic groups

Background: Radiation therapy has an established role in the multimodal management of rectal cancer. Despite consensus on the benefit of radiation therapy, the optimal timing of radiation administration—neoadjuvant vs. adjuvant—has been much debated and is not yet established. Our group has recently shown that race and ethnicity correlate with rectal cancer outcomes. Our objective was to investigate the impact that race and ethnicity may have on rectal cancer outcomes in relation to timing of radiation therapy.

Methods: We used the Los Angeles County Cancer Surveillance Program (CSP) to identify patients who underwent curative surgical resection for rectal adenocarcinoma from 1988-2006. Patients were stratified by race and ethnicity (white, black, Hispanic, and Asian) and timing of radiation therapy (neoadjuvant or adjuvant). Clinical and pathologic characteristics were compared and survival curves were analyzed by Kaplan-Meier method.

Results: Of the 7,908 surgically resected patients identified from CSP, 39% (n=3,107) received radiation therapy. Among the patients receiving radiation therapy, the majority of patients received adjuvant radiation therapy (58%; n=1,789). Stratified by race and ethnicity (white, n=1,613; black, n=283; Hispanic, n=608; Asian, n=435), there was no difference in overall survival based on neoadjuvant vs. adjuvant timing of radiation therapy for black patients (median survival [MS] 4.1 vs. 4.9 years, respectively; p=NS) and Hispanic patients (MS 7.6 vs. 6.9 years, respectively; p=NS). However, overall survival was significantly improved for neoadjuvant vs. adjuvant timing of radiation therapy in Asian patients (MS 10.6 vs. 6.5 years; p<0.001, respectively) and white patients (MS 8.4 vs. 6.5 years; p<0.001, respectively).

Conclusions: This is the first report to identify racial and ethnic differences in benefit derived from radiation therapy for rectal cancer. We observed that neoadjuvant radiation compared to adjuvant radiation selectively improved survival in white and Asian patients, but not Hispanic and black patients. The reasons for these differences in treatment efficacy between racial and ethnic groups warrant further investigation to optimize timing of therapy and achieve maximum therapeutic benefit in patients with rectal cancer.

Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B80.