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 [Cl], 1.6-1.8), Hispanic ethnicity (OR, 1.3; 95% Cl, 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% Cl, 0.3-0.3 and OR, 0.2; 95% Cl, 0.2-0.2 for women with 1 and >= 2 prior mammograms, respectively) nor overall physician service use (OR, 0.7; 95% Cl, 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% Cl, 0.9-1.5) among women with multiple stable comorbidities who received >= 2 screening mammograms, and 1.0 (95% Cl, 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. Cancer (C) 2011;117:3252-61. (C) 2011 American Cancer Society.