Has racial difference in cause-specific death improved in older patients with late-stage breast cancer?

Abstract

Background: Research on temporal mortality trends for stage IV breast cancer is limited, especially among older patients by race. We evaluated factors associated with overall, breast cancer-specific and other-cause mortalities using contemporary population data.

Patients and methods: Using the Surveillance, Epidemiology, and End Results-Medicare linked data, we identified older women (≥ 66 years) with stage IV breast cancer diagnosed in 2002-2009. Overall mortality was estimated by the Kaplan-Meier method, compared by log-rank tests, and modeled by Cox models. Competing risk analysis was used to evaluate breast cancer-specific and other-cause mortalities.

Results: The median overall survival time for non-Hispanic blacks improved from 8.6 months in 2002-2003 to 9.9 months in 2007-2009, whereas that for non-Hispanic whites improved from 12.1 to 14.8 months. In the multivariate model, the risk of breast cancer-specific death for patients diagnosed in 2007-2009 was significantly lower (P = 0.02), whereas the risk of other-cause mortality changed little (P = 0.88) compared with those risks for patients diagnosed in 2002-2003. Non-Hispanic blacks had the higher risk of both mortality types compared with non-Hispanic whites; a diagnosis time-race interaction term was not statistically significant for either cause of death.

Conclusion: Breast cancer-specific mortality among older women modestly improved from 2002 to 2009 across all races, but not other-cause mortality. Racial disparity in mortality persisted, but did not widen in this period. Efforts should be devoted to improving other-cause mortality for all women, with special attention toward decreasing breast cancer mortality for non-Hispanic black women.

Keywords: Medicare; SEER program; breast cancer-specific mortality; competing risk; older stage IV breast cancer; other-cause mortality.