Racial disparities in the development of breast cancer metastases among older women: a multilevel study.

BACKGROUND: Distant metastases are the most common and lethal type of breast cancer relapse. The authors examined whether older African American breast cancer survivors were more likely to develop metastases compared with older white women. They also examined the extent to which 6 pathways explained racial disparities in the development of metastases.
METHODS: The authors used 1992-1999 Surveillance, Epidemiology, and End Results (SEER) data with 1991-1999 Medicare data. They used Medicare's International Classification of Diseases, Ninth Revision, Clinical Modification codes to identify metastases of respiratory and digestive systems, brain, bone, or other unspecified sites. The 6 pathways consisted of patient characteristics, tumor characteristics, type of treatment received, access to medical care, surveillance mammography use, and area-level characteristics (poverty rate and percentage African American) and were obtained from the SEER or Medicare data.
RESULTS: Of the 35,937 women, 10.5% developed metastases. In univariate analysis, African American women were 1.61 times (95% confidence interval [CI], 1.54-1.83) more likely to develop metastasis than white women. In multivariate analysis, tumor grade, stage at diagnosis, and census-tract percentage African American explained why African American women were more likely to develop metastases than white women (hazard ratio, 0.84; 95% CI, 0.68-1.03).
CONCLUSIONS: Interventions to reduce late-stage breast cancer among African Americans also may reduce racial disparities in subsequent increased risk of developing metastasis. African Americans diagnosed with high-grade breast cancer could be targeted to reduce their risk of metastasis. Future studies should identify specific reasons why the racial distribution in census tracts was associated with racial disparities in the risk of breast cancer metastases. (c) 2009 American Cancer Society.