Racial differences in survival of female breast cancer in the Detroit metropolitan area.

Background: 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.
Methods: 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.
Results: 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.
Conclusions: Known factors that predict survival differences between African-American and white women are more prevalent among women younger than age 50.