Black-White Breast Cancer Incidence Trends: Effects of Ethnicity

Abstract

Recent reports of converging black and white breast cancer incidence rates have gained much attention, potentially foreshadowing a worsening of the black-white breast cancer mortality disparity. However, these incidence rates also reflect the sum of non-Hispanics and Hispanics that may mask important ethnicity-specific trends. We therefore assessed race- and ethnicity-specific breast cancer trends using the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) 13 Registries Database (1992-2014). Age-period-cohort models projected rates for 2015-2030. Results confirmed merging of age-standardized incidence rates for blacks and whites circa 2012, but not for non-Hispanic black (NHB) and non-Hispanic white (NHW) women. Incidence rates were highest for NHW women (n = 382 290), followed by NHB women (n = 51 074), and then Hispanic white women (n = 48 651). The sample size for Hispanic blacks was too small for analysis (n = 693). Notably, future incidence rates are expected to slowly increase (2015 through 2030) among NHW women (0.24% per year, 95% confidence interval [CI] = 0.17 to 0.32) and slowly decrease for NHB women (-0.14% per year, 95% CI = -0.15 to -0.13). A putative worsening of the black-white mortality disparity, therefore, seems unlikely. Ethnicity matters when assessing race-specific breast cancer incidence rates.

Figure 1.

Observed and projected incidence of invasive female breast cancer in the Surveillance, Epidemiology, and End Results (SEER) 13 registries by race and ethnicity. A) Observed (1992–2014) and projected (2015–2030) age-standardized incidence rates of invasive breast cancer per 100 000 woman-years for all white (squares) and all black (circles) women between the ages of 30 and 84 years in the SEER 13 registries. An arrow points to the previously reported convergence in rates between all white and all black women for the year 2012 (5). B) Observed (1992–2014) and projected (2015–2030) age-standardized incidence rates of invasive breast cancer per 100 000 woman-years for non-Hispanic white (stars), non-Hispanic black (diamonds), and Hispanic women (triangles) between the ages of 30 and 84 years in the SEER 13 registries. In each panel, a vertical reference line separates the observed from the forecast period. Shaded bands show point-wise 95% confidence limits for the forecasted incidence rates, denoted to the right of the vertical reference line.