P2-14-02: NCIC CTG MA.27: Clinical Tolerability and Overall Survival of Racial and Ethnic Minority Women on Aromatase Inhibitor Therapy.

Abstract Background Aromatase inhibitors (AIs) are standard adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer. We previously reported that racial/ethnic minority women receiving an AI in NCIC CTG MA.17 experienced fewer hot flashes, fatigue, and arthralgias than Caucasians (Moy B et al. Ann Oncol 2006;17:1637). Here we examined whether race affected clinical outcomes in the MA.27 AI trial comparing exemestane (E) with anastrozole (A). Methods: Fisher's exact test was used to compare observed side effects (0 vs grades 1–5) between minority and Caucasian women. Adverse events (AE), including menopausal symptoms, were assessed according to the Common Terminology Criteria of the National Cancer Institute (version 3.0). ITT univariate test of race effects on overall survival (OS) was determined with a stratified log-rank test, while multivariate testing was with stratified Cox regression. Results: Among 7312 for whom race was known, distribution was: Caucasian (n=6939; 95%); black (n=235; 3%); Asian/Native Hawaiian/Pacific Islander (n=93); 1%; American Indian (n=39; 1%); and mixed race (n=6). Among women treated with E, minorities reported a significantly lower incidence of hot flashes (45% vs. 56%; p=0.003) and fatigue (34% vs. 46%; p=0.001) compared to Caucasians. Similarly with A, minority women reported significantly fewer hot flashes (47% vs. 58%; p=0.002) and lower cholesterol (12% vs. 18%; p=0.01); however, they reported more headaches than Caucasians (16% vs. 10%; p=0.01). Caucasian women were more likely to discontinue therapy due to AE or side effects (32% vs. 24%). There was a significant OS interaction (p=0.02) between race and treatment with minority women on E having fewer deaths than those on A. Caucasian women had HR of E to A of 0.98 (95% CI 0.81−1.20), p=0.85, while minorities had HR of E to A of 0.72 (95% CI 0.33−1.58), p=0.41. Conclusions: Minority women tolerated AIs better and were also more compliant than Caucasians, supporting our previous findings. A significant interaction between race and type of AI therapy for OS was seen, favoring exemestane in minority women. Replication of these findings in larger cohorts is necessary. Since race/ethnicity may serve as a surrogate for genetic differences, our findings suggest pharmacogenomic differences which require further research. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-14-02.

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