Efficacy of systemic adjuvant therapy for breast cancer in African-American and Caucasian women.

Abstract

Observed variations in breast cancer survival by racial/ethnic background have been attributed to many factors, including differences in clinical and pathologic disease features at diagnosis and economic resource inequities that may affect treatment access and quality. In this report, we examine outcomes for African-American and Caucasian breast cancer patients participating in selected randomized clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP) to determine whether prognosis or efficacy of systemic adjuvant therapy differed between these groups. Randomized clinical trials offer the advantages of a similar disease stage and a uniform treatment plan for all participants. Patients from four NSABP trials enrolling patients from 1982 through 1994 with axillary lymph node-negative disease (543 African-American and 7582 Caucasian) and three trials enrolling patients from 1984 through 1991 with axillary lymph node-positive disease (548 African-American and 4986 Caucasian) were included. Disease-free survival (DFS), which was defined as time on study free of breast cancer recurrence, second primary cancer, or death preceding these events, and survival risk ratios (RRs) with two-sided 95% confidence intervals (CIs) for African-Americans versus Caucasians were computed from Cox proportional hazards models that included relevant prognostic covariates. Treatment benefits for the therapies evaluated in these trials were estimated separately for African-Americans and for Caucasians. Among patients with lymph node-negative disease, African-Americans had similar DFS rates to Caucasians (African-American/Caucasian RR = 1.06, 95% CI = 0.92 to 1.23) but had modestly greater mortality rates (RR = 1.21, 95% CI = 1.01 to 1.46). Among lymph node-positive patients, DFS was similar (RR = 1.04, 95% CI = 0.93 to 1.17) and survival was again less favorable for African-Americans (RR = 1.18 95% CI = 1.03 to 1.34). Survival excluding deaths most likely attributable to causes other than cancer was similar between African-Americans and Caucasians (RR = 1.08 [95% CI = 0.88 to 1.33] for lymph node-negative patients and RR = 1.09 [95% CI = 0.96 to 1.25] for lymph node-positive patients). Among lymph node-negative and lymph node-positive patients, African-Americans and Caucasians realized comparable benefit from either the addition of chemotherapy or tamoxifen to surgery alone or the addition of chemotherapy to tamoxifen. In summary, African-American women and Caucasian women who were diagnosed at a comparable disease stage and were similarly treated tended to experience similar breast cancer prognosis. However, a mortality deficit persisted for African-American women relative to Caucasian women, which may be in part due to greater mortality from noncancer causes among African-Americans. Benefit from systemic adjuvant therapy for recurrence and mortality reduction was comparable between African-Americans and Caucasians. This study and investigations in other health-care settings suggest that African-American women and Caucasian women with breast cancer derive a similar benefit from systemic adjuvant therapy when it is administered in accordance with their clinical and pathologic disease presentation.