Understanding mechanisms of racial disparities in breast cancer: an assessment of screening and regular care in the Carolina Breast Cancer Study

Abstract

Purpose: Screening history influences stage at detection, but regular preventive care may also influence breast tumor diagnostic characteristics. Few studies have evaluated healthcare utilization (both screening and primary care) in racially diverse screening-eligible populations.

Methods: This analysis included 2,058 women age 45-74 (49% Black) from the Carolina Breast Cancer Study, a population-based cohort of women diagnosed with invasive breast cancer between 2008 and 2013. Screening history (threshold 0.5 mammograms per year) and pre-diagnostic healthcare utilization (i.e. regular care, based on responses to "During the past ten years, who did you usually see when you were sick or needed advice about your health?") were assessed as binary exposures. The relationship between healthcare utilization and tumor characteristics were evaluated overall and race-stratified.

Results: Among those lacking screening, Black participants had larger tumors (5 + cm) (frequency 19.6% vs 11.5%, relative frequency difference (RFD) = 8.1%, 95% CI 2.8-13.5), but race differences were attenuated among screening-adherent participants (10.2% vs 7.0%, RFD = 3.2%, 0.2-6.2). Similar trends were observed for tumor stage and mode of detection (mammogram vs lump). Among all participants, those lacking both screening and regular care had larger tumors (21% vs 8%, RR = 2.51, 1.76-3.56) and advanced (3B +) stage (19% vs 6%, RR = 3.15, 2.15-4.63) compared to the referent category (screening-adherent and regular care). Under-use of regular care and screening was more prevalent in socioeconomically disadvantaged areas of North Carolina.

Conclusions: Access to regular care is an important safeguard for earlier detection. Our data suggest that health equity interventions should prioritize both primary care and screening.

Keywords: Cancer screening; Cohort study; Disparities; Healthcare; Mammography; Tumor presentation.

Fig 1

Tumor characteristics according to regular care and screening. Risk ratios (RR) and 95% confidence intervals were estimated from bivariate log-binomial regression models. Estimates represent the relative risk of the indicated outcome for those lacking care compared to those with care. Results are shown for A) no regular care, B) no regular care - by race, C) non-adherence to biennial screening, and D) non-adherence to biennial screening - by race

Fig 2

Simultaneous assessment of regular care and screening. Kernel density plots show a smoothed, non-parametric distribution of mammography receipt (units of screening mammograms per year). Distributions are compared A) between participants with and without regular care, and B) between Black and non-Black participants overall with restriction to participants with regular care. C) Risk ratios and confidence intervals were estimated from log binomial regression models. Each estimate corresponds to the relative risk for the 3 comparator groups relative to the reference group. The reference group includes participants with regular care and screening adherence. The “double exposed” index group include participants without regular care and are non-adherent to screening guidelines. The advanced stage RR for no regular care, screening-adherent is not shown because there were only 3 participants in this exposure-outcome and the CI was not stable.

Fig 3

Racial differences in tumor characteristics by receipt of regular care and screening. Frequency (expressed as a percentage) of unfavorable tumor characteristics are reported for Black and non-Black women according to receipt of preventive care. Results are shown for A) regular care and B) screening