Abstract C087: Differences in estrogen receptor-negative breast cancer by race and SEER registry

Background: Estrogen receptor-negative (ERN) breast cancer is an early-stage, more aggressive breast cancer subtype. ERN breast cancer incidence is highest in African American women compared with other races, as well as in southern US regions. However, recent studies have shown that ERN breast cancer incidence is declining for women overall. We sought to understand whether ERN breast cancer is declining similarly in all races, age groups, and SEER registries. Methods: Data from Surveillance, Epidemiology, and End-Results (SEER) Program 13 registries from 1990-2014, as well as the remaining five SEER 18 registries from 2000-2014, were used to observe ERN breast cancer incidence rates among non-Hispanic white (NHW) and non-Hispanic black (NHB) women by age group (30-39, 40-49, 50-69, 70-84 years). Age-period-cohort modeling was used and extended, allowing for regional heterogeneity by population (i.e. SEER registry), to estimate differences in longitudinal age trends and net drifts by race and SEER registry. Results: Among all age groups within all SEER 18 registries, ERN breast cancer incidence rates were higher for NHB compared to NHW women. Furthermore, ERN rates have been decreasing for both NHW and NHB women. For the entire SEER population, women ages 40-49 years compared to other age groups demonstrated the fastest declines in ERN breast cancer incidence, with a net drift of -3.5%/year (95% CI: -4.0, -3.1) for NHW women, and -3.1%/year (-3.8, -2.2) for NHB women. Among the youngest women (30-39 years), ERN rates have declined faster in NHB compared to NHW women, with net drifts of -2.7%/year (-3.5, -1.8) and -1.7%/year (-2.2, -1.2), respectively; for all other age groups, rates have declined faster for NHW compared to NHB women. For NHW women of all age groups, there was relatively little between-registry variability in trends, with net drift standard deviations of 0.5%/year (0.02, 1.3) for 30-39 years, 0.8%/year (0.4, 1.2) for 40-49 years, 0.6%/year (0.4, 0.9) for 50-69 years, and 0.7%/year (0.4, 1.1) for 70-84 years. For NHB women, rates have also decreased similarly across registries in the youngest age group (30-39 years), with between-registry net drift standard deviation of 0.4%/year (0.01, 1.5); however, for NHB of all other age groups, there was more between-registry variability with net drift standard deviations of 1.0%/year (0.1, 2.1) for 40-49 years, 1.0%/year (0.4, 1.8) for 50-59 years, and 1.2%/year (0.4, 2.4) for 70-84 years. These standard deviations reflect that ERN rates have been declining more slowly in southern registries (i.e., Greater Georgia, Atlanta, Rural Georgia, and Louisiana) for older NHB women. Conclusion: Among NHW women, decreases in ERN breast cancer incidence have been similar across age groups and SEER registries. Among NHB women, ERN rates have also been decreasing; however, these decreases vary by age and SEER registry, which may offer etiologic clues. Further investigation is needed to understand which factors are contributing to these trends. Citation Format: Brittny C. Davis Lynn, Pavel Chernyavskiy, William F. Anderson, Gretchen L. Gierach, Philip S. Rosenberg. Differences in estrogen receptor-negative breast cancer by race and SEER registry [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C087.