Temporal trends in the black/white breast cancer case ratio for estrogen receptor status: disparities are historically contingent, not innate

Objective For at least three decades, many investigators have reported on the US black/white breast cancer case ratio for estrogen receptor (ER) status as if it reflected an intrinsic biological difference. In light of racial/ethnic differences in declines in the incidence of ER+ breast cancer, as linked to changing use of hormone therapy, we empirically tested whether the black/white breast cancer estrogen receptor ratio has changed over time. Methods We examined temporal trends in the odds of being ER+ among white as compared to black women among all cases of invasive breast cancer occurring among women residing in the catchment area of the SEER 13 Registries Database between 1992 and 2005. Results During the study period, the odds of being ER? among the white compared to black cases increased from 1992 to 2002 (a statistically significant joinpoint; p < 0.05; peak odds ratio (2002) = 2.25 (95% confidence interval 2.13, 2.39)). Thereafter, the odds ratio leveled off (post-2002 slope not significantly different from zero; p = 0.326). Among women aged 45-54, moreover, the post-2002 decline tended toward statistical significance (p = 0.0891). Conclusions The results suggest the black/white breast cancer case estrogen receptor ratio is historically contingent, not innate.