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. Cancer 2011. © 2011 American Cancer Society.