Geographic disparities in age-specific breast cancer incidence trends in the United States, 2001-2018

Abstract Background: Temporal trends in breast cancer (BC) incidence rates are shown to vary by age and race/ethnicity in the United States (U.S.), but less is known about whether these trends also vary by geography. Methods: We used data from the U.S. Cancer Statistics (USCS) database, a population-based surveillance system of cancer registries covering 99% of the U.S. population, to evaluate trends in age-specific BC incidence rates from 2001-2018 by geography. Incidence rates were calculated for 15-year age groups, including 25-39, 40-54, 55-69, and 70-84 years. We calculated age-specific BC incidence rates stratified by state, region (Midwest, Northwest, South, West), and metropolitan or non-metropolitan designation based on Rural-Urban Continuum Codes. We also calculated rates further stratified by race/ethnicity. For each geographic subgroup, we calculated the average annual percent change (AAPC) in BC incidence using Joinpoint software; multiple permutation testing was used to identify inflection points in trends. Results: We found that BC incidence significantly increased from 2001-2018 in 18, 16, 3, and 15 states, respectively, for the age groups of 25-39, 40-54, 55-69, and 70-84 years. BC incidence significantly decreased in 3, 2, 15, and 1 state(s), respectively, for the age groups of 25-39, 40-54, 55-69, and 70-84 years. We identified regional differences in age-specific BC incidence trends from 2001-2018. In the 25-39 years age group, a significant increase in BC incidence was observed in the Northeast (AAPC=0.56), Midwest (AAPC=0.48), and West (AAPC=0.67), but not in the South. The Northeast and Midwest also experienced a significant increase in BC incidence in the 40-54 years age groups (AAPCs=0.52 and 0.38, respectively). The Midwest and West experienced a significant decrease in BC incidence in the 55-69 years age group (AAPCs = -0.35 and -0.89, respectively). The South was the only region to experience a significant increase in BC incidence in the 70-84 years age group (AAPC=0.28). Trends were mostly consistent between metropolitan and non-metropolitan areas within regions, except that BC incidence in the 55-69 years age group significantly increased in non-metropolitan areas of the South (AAPC = 0.27), but not metropolitan areas of the South. Regional differences were also observed when we further stratified BC incidence rates by race/ethnicity. Conclusions: These findings suggest that geography should be considered when measuring and addressing disparities in BC incidence rates. Additional studies are needed to identify the geographically patterned risk factors, such as certain environmental exposures, that may be contributing to these trends in BC incidence rates. Regional differences in screening practices may also be contributing to trends in older age groups. Citation Format: Rebecca D. Kehm, Josephine M. Daaboul, Mary Beth Terry. Geographic disparities in age-specific breast cancer incidence trends in the United States, 2001-2018 [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C072.