Pre-diagnosis oophorectomy, estrogen therapy and mortality in a cohort of women diagnosed with breast cancer

INTRODUCTION: Pre-diagnosis oophorectomy and estrogen therapy could impact mortality due to breast cancer and cardiovascular disease (CVD) among breast cancer survivors. Elective bilateral oophorectomy at the time of hysterectomy for benign conditions is not uncommon among US women. METHODS: We examined the association between pre-diagnosis total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAHBSO) and both overall and cause-specific mortality in the Collaborative Breast Cancer Studies cohort. Medical history and prior estrogen use were collected during standardized telephone interviews. Vital status, including date and cause of death, was obtained by linkage with the National Death Index. Multivariate hazard ratios (HR) and 95% confidence intervals (CI) for cause-specific mortality were calculated using Cox proportional hazards regression. RESULTS: Seventeen percent (N = 1,778) of breast cancer survivors (mean age at diagnosis = 63.5) reported pre-diagnosis TAHBSO. During follow-up (mean = 9.5 years), 2,856 deaths occurred, including 1,060 breast cancer deaths and 459 CVD deaths. Breast cancer deaths occurred a median of 5.1 years after diagnosis; CVD deaths occurred further from diagnosis (median = 9.7 years). Women who reported pre-diagnosis TAHBSO had a 16% decrease in all-cause mortality (HR = 0.84; 95% CI: 0.76, 0.92) compared to those with an intact uterus and ovaries. This overall decrease reflected a 27% lower breast cancer mortality among women who never used postmenopausal hormones (HR = 0.73; CI: 0.55, 0.96) and 43% lower CVD risk among women who reported using estrogen (HR = 0.57; CI: 0.39, 0.83) after TAHBSO. CONCLUSIONS: Information on prior TAHBSO and estrogen use can inform risk of death from both breast cancer and cardiovascular disease among breast cancer survivors.