The comparative effectiveness of biologic agents among non-hispanic black (NHB) patients with metastatic colorectal cancer (mCRC): Preliminary results of a SEER-medicare analysis.

Abstract

e19059 Background: Biologic agents (bevacizumab, cetuximab, panitumumab) have improved the overall survival (OS) of patients with mCRC. However, clinical trials are plagued by low representation of NHB patients, and a disproportionately high (>90%) accrual of non-Hispanic whites (NHW). As a result, the real world benefit among NHB patients in unknown. Comparative effectiveness research is an approach for effectively addressing this drawback. Methods: Utilizing the SEER-Medicare linked database, we identified 5,728 patients with mCRC diagnosed between 2004 and 2011 who received chemotherapy (CT; oxaliplatin, irinotecan, 5-FU, capecitabine) alone or chemotherapy with a biologic agent (CBT). OS was examined using the Kaplan-Meier method and a weighted semi-parametric accelerated failure time model. A propensity score model approach was undertaken to further account for potential treatment selection bias. Results: Overall, 88% were NHW and 12% NHB patients. The median age at diagnosis was 73 and 70 years and exposure to biologics was 71.2% and 71.4%, respectively. NHB patients had more women, were single, had lower median incomes, better differentiated tumors, less rectal primary cancers, more right sided tumors, and a worse Charleson co morbidity index. There was no difference in the receipt of 1 (72%) vs > 2 (28%) lines of therapy. The median OS was 11 and 12 months (m) in the CT-alone group, and 21 and 22 m in CBT group, among NHW and NHB, respectively. Based on an unadjusted analysis, receipt of biologics, younger age, left sided primary, well/moderate differentiation, being married, more lines of CT, and lower prevalence of co-morbidity were associated with improved OS. We also performed multiple imputations to properly account for the missing data. Among NHW, median OS was 21 vs 11 m in the CBT and CT groups, respectively (effect 1.47, 95% CI 1.36-1.60, p = 0.0000). Among NHB, median OS was 22 vs 12 m in the CBT and CT groups, respectively (effect 1.48, 95% CI 1.23-1.88, p = 0.0000). All comparisons maintained significance when adjusted for multiple comparisons. We found no interaction between biologics and race (p = 0.8743). On subgroup analysis, those patients receiving both classes of biologics (anti EGFR and anti VEGF) had the best outcome. Conclusions: In this cohort of older patients, CBT was associated with longer survival, regardless of race. Clinicians should offer CBT therapy to all patients to maximize their clinical benefit, factoring in clinical variables, but not their race.