Ramanathan, R. K.

3503 Background: The association between race & toxicity or response to systemic chemotherapy is poorly understood. We correlated relevent polymorphisms with toxicity & outcome data in AA & C patients (Pts) enrolled in N9741, a large randomized MCRC trial. Methods: Toxicity, response rate (RR), time to progression (TTP), overall survival (OS), & dose intensity (DI) were examined as a function of race in 1412 Pts enrolled on IFL, both full and reduced dose, FOLFOX, or IROX including 486 Pts with pharmacogenomic data. Accrual by race permitted comparison of C (n=1297) to AA (n=112). Results: C & AA were similar in disease extent, PS, gender, prior adjuvant treatment, and DI at cycles 1, 3, 6, or 12. The impact of race on RR, toxicity & the distribution of four relevent drug metabolism genotypes are in the table . AA had lower RR overall & in each treatment arm. Lower toxicity rates were seen in AA Pts, mainly due to less diarrhea, as measured by both CTC V2 & patient reported outcome data. These relationships were maintained in multivariate models adjusting for arm, age, gender, & PS. In these multivariate models, the odds ratio between RR and race was 1.72 (p=0.012) (29% AA vs 41% C) & for severe toxicity the odds ratio was 1.76 (p=0.006) (34% AA vs 48% C). Overall, race was not a significant predictor of TTP or OS (p > 0.50 for each). The hazard ratio comparing FOLFOX to IFL for C was 0.67 and for AA was 0.55. TTP for FOLFOX was superior to both IFL and IROX for both C & AA. Significant differences in pharmacogenetic variants were observed between C & AA, although the sample size for investigating the three-way combination of Rx, race, & pharmacogenomics is too small (36 AA) to draw definitive conclusions. Conclusions: It appears that AA have less toxicity & a lower RR than C when treated with standard MCRC regimens. Different frequencies of polymorphisms in genes relevent to drug metabolism may help explain these clinical differences. [Table: see text] [Table: see text]