Background: Non-Hispanic Black (NHB) women have had historically lower rates of postmenopausal breast cancer compared to non-Hispanic White (NHW) women in the United States (US). However, since 1999, there has been a decline of breast cancer rates among NHW and a rise among NHB women, leading to a potential convergence. It is unclear whether these trends by race/ethnicity are driven by a certain subgroup, so we estimated trends in breast cancer incidence by race/ethnicity within subgroups of stage, poverty, and geographic factors. Methods: We limited our study population to women aged 50-79 years. We used data from 1999-2016 from the North American Association of Central Cancer Registries (NAACCR), which covers over 90% of the US population. We estimated longitudinal trends in breast cancer incidence by a combination of race/ethnicity (NHB, NHW, Hispanic) and the following variables: stage (local, regional, distant), county-level percent persons living below the federal poverty line (FPL) (<5%, 5-9.99%, 10-20%, >20%), county-level urban/rural status, and US Census geographic region (Northeast, Midwest, South, West). We estimated the average annual percent change (AAPC) in breast cancer incidence rates using the National Cancer Institute JoinPoint Regression Program 126.96.36.199. We report only statistically significant AAPCs, assuming non-significant trends indicate a stable incidence rate over the given time period. Results: From 1999-2016, the breast cancer incidence rate increased on average by 0.5% per year for NHB women and was non-significant/stable for NHW and Hispanic women. Among NHB women, the AAPC was 1.2% for local stage and 1.3% for distant stage. In contrast, the AAPC was -1.3% and -0.7% for regional stage among NHW and Hispanic women, respectively. By county-poverty level, there was a 0.8% AAPC among NHB women living in a county with 5-9.99% living below the FPL. The AAPCs among NHW women living in counties with 5-9.99%, 10-19.99%, and >20% below the FPL were -0.7%, -0.6%, and -0.7%, respectively. Among rural counties, the AAPC was 1.2% among NHB women and -0.5% among NHW women. Lastly, the AAPC was 0.7% and 1.0% among NHB women living in the South and Northeast, respectively. The AAPC was 0.6% among Hispanic women and -0.4% among NHW women living in the Northeast. Conclusion: In contrast to NHW and Hispanic women, the incidence rate of breast cancer is rising among several subgroups of NHB women, including women in the Northeast, South, rural counties, and counties with less poverty. The increasing incidence among NHB women for both local and distant stage breast cancers suggests the trend may not be due to increases in screening alone. There is an increasing burden of breast cancer among these subgroups, which may exacerbate existing disparities and warrants further investigation and targeting for breast cancer prevention.
Citation Format: Maneet Kaur, Corinne E. Joshu, Kate E. Dibble, Junrui Lyu, Avonne E. Connor. Examining converging breast cancer incidence rates by race/ethnicity, poverty, and geography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB085.