Contrasting trends in racial disparities in breast cancer, 1985 - 2004.

A50

INTRODUCTION: In the United States, age-adjusted breast cancer mortality rates became higher among Black women than White women in the late 1980’s, and this disparity has been widening since then. To further asses this racial disparity, we explored breast cancer trends using the NCI’s Surveillance, Epidemiology, and End Results (SEER) database for the calendar period 1985 to 2004. We analyzed temporal trends in Black-White rate ratios for breast cancer mortality (MRR), breast cancer incidence (IRR), and hazard of breast cancer death among women living with the disease (HRR). We used generalized linear regression models to determine the significance of trends and age interactions.
 RESULTS: MRR increased over time with significant variation for different age groups (F test = 5.77, P = 0.0008). The greatest Black-White racial disparity was observed among women ages < 40 years diagnosed in 2004 (MRR = 2.1; 95% CI = 2.0-2.2). In contrast, age-specific IRRs remained relatively stable over time, as did the proportions of ER+ and ER- tumors diagnosed in Black and White women (Blacks had relatively less ER+ and more ER- tumors). To assess the residual effect of race on breast cancer survival, we analyzed trends in the hazard of death from breast cancer among cohorts of cases, adjusted for age-at-diagnosis, ER expression, year of diagnosis, tumor grade, and AJCC stage. Although absolute hazard rates improved in both Black and White women over time, the fully-adjusted HRR was persistently elevated (HRR = 1.37; 95% CI 1.31 - 1.43) except for women older than 70 years with ER- tumors (HRR = 0.90; 95% CI 0.77 - 1.02).
 CONCLUSIONS: The widening Black-White mortality disparity has occurred on a background of stable incidence patterns and persistent improvement in hazard rates. Therefore, it may partially reflect greater relative response to treatment of ER+ breast cancers, which are consistently less common in younger Black women. Developing more effective targeted therapies for ER- breast cancer subtypes that are more common in Black women may reduce racial disparities in breast cancer mortality.