Absence of an anticipated racial disparity in interval breast cancer within a large health care organization

Abstract

PURPOSE Compared to non-Latina (nL) white women, nL Black women are diagnosed with more aggressive breast cancers, which in turn should be more likely to go undetected on screening mammography and subsequently arise as interval breast cancer (IBC). We sought to estimate the extent of an anticipated racial disparity in IBC within a single, large health care organization. METHODS The present analyses focuses on 4,357 breast cancers diagnosed between 2001 and 2012 and within 18 months of a screening mammogram (N=714,218). We used logistic regression with model-based standardization (predictive margins) to estimate adjusted prevalence differences (PD) corresponding to a racial disparity in IBC. RESULTS Overall, prevalence of IBC within 18 months was 20.7 percent. Contrary to expectation, in patient-adjusted models, there was no IBC racial disparity (percentage point disparity = −2.1, 95% CI: −4.7, 2.6). However, when controlling for facility characteristics, including proportion nL Black patients, the model coefficient for the IBC disparity reversed sign and changed substantially (p<0.0001) and a racial disparity emerged (percentage point disparity = +5.1, 95% CI: −0.3, 9.9). CONCLUSIONS The sorting of patients by race across facilities appears to have mitigated an otherwise anticipated disparity in interval breast cancer. Possible explanations are discussed.

Validation of the breast cancer surveillance consortium model of breast cancer risk

“…The Chicago registry collects data on mammography examinations from a large health care delivery organization with facilities throughout metropolitan Chicago [6]. We included women ages 35 to 74 years who had at least one mammogram between 2001 and 2012 who were not diagnosed with breast cancer within 3 months of the index mammogram.…”

“…We grouped benign diagnoses as non-proliferative, proliferative without atypia, proliferative with atypia, or lobular carcinoma in situ [7]. We linked to the Illinois Sate Cancer Registry and hospital tumor registry and pathology sources to identify breast cancer diagnoses [6].…”

“…Younger women screened for breast cancer prior to most guideline recommendations for screening (ages 35-45) are likely at higher than average risk for breast cancer, so a model based on average risk would be expected to underestimate risk for this younger population. Second, the prevalence of obese (19%) and morbidly obese women (16%) in the Chicago cohort is high [6]. There is a strong association between body mass index (BMI) and breast density and between BMI and breast cancer incidence.…”