Comorbidities and mammography use interact to explain racial/ethnic disparities in breast cancer stage at diagnosis.

BACKGROUND: Interactions with comorbidity burden and comorbidity-related care have not been examined as potential explanations for racial/ethnic disparities in advanced-stage breast cancer at diagnosis.
METHODS: The authors used linked Surveillance, Epidemiology, and End Results-Medicare data to determine whether comorbidity burden and comorbidity-related care are associated with stage at diagnosis, whether these associations are mediated by mammography use, and whether they explain racial/ethnic disparities. Stage at diagnosis and mammography use were analyzed in multivariate regression models, adjusting for comorbidity burden and comorbidity-race interactions among 118,742 women diagnosed with breast cancer during 1993 to 2005.
RESULTS: Mammography utilization was higher among women with ≥ 3 stable comorbidities than among those without comorbidities. Advanced stage at diagnosis was associated with black race (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.6-1.8), Hispanic ethnicity (OR, 1.3; 95% CI, 1.2-1.5), unstable comorbidity, and age ≥ 80 years. Mammography was protective in all racial/ethnic groups, but neither mammography use (OR, 0.3; 95% CI, 0.3-0.3 and OR, 0.2; 95% CI, 0.2-0.2 for women with 1 and ≥ 2 prior mammograms, respectively) nor overall physician service use (OR, 0.7; 95% CI, 0.7-0.8 for women with ≥ 16 visits) explained the association between race/ethnicity and stage at diagnosis. The black/white OR fell to 1.2 (95% CI, 0.9-1.5) among women with multiple stable comorbidities who received ≥ 2 screening mammograms, and 1.0 (95% CI, 0.8-1.3) among mammography users with unstable comorbidities.
CONCLUSIONS: Comorbidity burden was associated with regular mammography and earlier stage at diagnosis. Racial/ethnic disparities in late stage disease were reduced among women who received both regular mammograms and comorbidity-related care.