Causes of death and relative survival of older women after a breast cancer diagnosis

Abstract

Purpose: To understand the impact of breast cancer on older women's survival, we compared survival of older women diagnosed with breast cancer with matched controls. METHODS Using the linked 1992 to 2003 Surveillance, Epidemiology, and End Results (SEER) -Medicare data set, we identified women age 67 years or older who were newly diagnosed with ductal carcinoma in situ (DCIS) or breast cancer. We identified women not diagnosed with breast cancer from the 5% random sample of Medicare beneficiaries residing in SEER areas.We matched patient cases to controls by birth year and registry (99% or 66,039 [corrected] patient cases matched successfully). We assigned the start of follow-up for controls as the patient cases' date of diagnosis. Mortality data were available through 2006. We compared survival of women with breast cancer by stage with survival of controls using multivariable proportional hazards models adjusting for age at diagnosis, comorbidity, prior mammography use, and sociodemographics. We repeated these analyses stratifying by age.

Results: Median follow-up time was 7.7 years. Differences between patient cases and controls in sociodemographics and comorbidities were small (< 4%). Women diagnosed with DCIS (adjusted hazard ratio [aHR], 0.7; 95% CI, 0.7 to 0.7) or stage I disease (aHR, 0.8; 95% CI, 0.8 to 0.8) had slightly lower mortality than controls.Women diagnosed with stage II disease or higher had greater mortality than controls (stage II disease:aHR, 1.2; 95% CI, 1.2 to 1.2). The association of a breast cancer diagnosis with mortality declined with age among women with advanced disease [corrected].

Conclusion: Compared with matched controls, a diagnosis of DCIS or stage I breast cancer in older women is associated with better [corrected] survival, whereas a diagnosis of stage II or higher breast cancer is associated with worse survival.

Fig 1.

Overall survival of women age 67 years and older by breast cancer stage and of their controls. We excluded women with unknown stage and their matches for these analyses. DCIS, ductal carcinoma in situ.