Mortality and Risk of Cancer After Prophylactic Bilateral Oophorectomy in Women With a Family History of Cancer

BACKGROUND: Current international guidelines recommend systemic hormone therapy (HT) to oophorectomized women until the age of natural menopause. Despite an inherited predisposition to estrogen-dependent malignancies, the guidelines also apply to women oophorectomized because of a family history of cancer. The objective of this study was to investigate the impact of HT on mortality and risk of cancer in women oophorectomized because of a family history of cancer. METHODS: A nationwide, population-based cohort was used to study women oophorectomized because of a family history of cancer (n = 2002). Comparison cohorts included women from the background population individually matched on age (n = 18( )018). Oophorectomized women were subdivided into three groups: oophorectomized at 1) age 45 years or younger not using HT, 2) age 45 years or younger using HT, 3) older than age 45 years, and their respective population comparison cohorts. RESULTS: Women oophorectomized at age 45 years or younger using HT had increased overall mortality (mortality rate ratio [MRR] = 3.45, 95% confidence interval [CI] = 1.53 to 7.79), mortality because of cancer (MRR = 5.67, 95% CI = 1.86 to 17.34), and risk of overall cancer (incidence rate ratio [IRR] = 3.68, 95% CI = 1.93 − 6.98), primarily reflected in an increased risk of breast cancer (IRR = 4.88, 95% CI = 2.19 − 10.68). Women oophorectomized at age 45 years or younger not using HT and women oophorectomized at older than age 45 years did not have increased mortality, mortality because of cancer, or risk of overall cancer, but they had increased risk of breast cancer (IRR = 2.64, 95% CI = 1.14 to 6.13, and IRR = 1.72, 95% CI = 1.14 to 2.59, respectively). CONCLUSIONS: Use of HT in women oophorectomized at age 45 years or younger with a family history of cancer is associated with increased mortality and risk of overall cancer and breast cancer. Our study warrants further investigation to establish the impact of HT on mortality and cancer risk in oophorectomized women with a family history of cancer.