In the United States, breast cancer survival is worse among African-American women compared with white women. This difference in survival is likely due to several factors, including tumor biology and/or access to care. In this analysis, we evaluated the effects of sociodemographic and clinical variables on differences in breast cancer survival among African-American and white women.
The study population included 10,502 women (82% white, 18% African-American), diagnosed between 1988 and 1992 and identified through the Metropolitan Detroit Cancer Surveillance System, a member of the Surveillance, Epidemiology and End-Results (SEER) Program. Cox proportional hazards regression was used to estimate the relative risk of death comparing African-American women with white women after controlling for variables believed to influence survival.
The mean age at diagnosis was 61 years and average length of follow-up was 34 months (range, 1–78 months). African-American women were more likely to present with regional or distant disease (45%) than were white women (37%). Although white women had better survival than African-American women during the first 4 years postdiagnosis (P < 0.0001), there were no significant differences in survival by race for women who lived longer than 4 years (P = 0.64). There was a significant interaction between age and race. The unadjusted relative risk of dying for African-American women compared with white women was 2.35 (95% confidence interval [CI], 1.88-2.93) for women younger than 50 years of age, and was 1.66 (95% CI, 1.46-1.88) for women age 50 years or older. After controlling for age, tumor size, stage, histologic grade, census-derived socioeconomic status, and residency training status, the relative risk was 1.68 (95% CI, 1.27-2.24) for women younger than 50 years of age and 1.33 (95% CI, 1.13-1.56) for women age 50 years and older. Adjustment for marital status, hospital size, and the proportion of Medicaid or Medicare discharges had no further effect on the relative risk.
Known factors that predict survival differences between African-American and white women are more prevalent among women younger than age 50. Cancer 1996;77:308-14.