Bone health after RRBSO among BRCA1/2 mutation carriers: a population-based study

Objective: Examine the risks of fractures and osteoporosis after risk-reducing bilateral salpingo-oophorectomy (RRBSO) among women with BRCA1/2 mutations. Methods: In this retrospective population-based study in British Columbia, Canada, between 1996 to 2017, we compared risks of osteoporosis and fractures among women with BRCA1/2 mutations who underwent RRBSO before the age of 50 (n=329) with two age-matched groups without known mutations: 1) women who underwent bilateral oophorectomy (BO) (n=3,290); 2) women with intact ovaries who had hysterectomy or salpingectomy (n=3,290). Secondary outcomes were: having dual-energy X-ray absorptiometry (DEXA) scan, and bisphosphonates use. Results: The mean age at RRBSO was 42.4 years (range, 26-49) and the median follow-up for women with BRCA1/2 mutations was 6.9 years (range, 1.1-19.9). There was no increased hazard of fractures for women with BRCA1/2 mutations (adjusted hazard ratio [aHR]=0.80; 95% confidence interval (CI)=0.56-1.14 compared to women who had BO; aHR=1.02; 95% CI=0.65-1.61 compared to women with intact ovaries). Among women who had DEXA-scan, those with BRCA1/2 mutations had higher risk of osteoporosis (aHR=1.60; 95% CI=1.00-2.54 compared to women who had BO; aHR=2.49; 95% CI=1.44-4.28 compared to women with intact ovaries). Women with BRCA1/2 mutations were more likely to get DEXA-scan than either control groups, but only 46% of them were screened. Of the women with BRCA1/2 mutations diagnosed with osteoporosis, 36% received bisphosphonates. Conclusion: Women with BRCA1/2 mutations had higher risk of osteoporosis after RRBSO, but were not at increased risk of fractures during our follow-up. Low rates of DEXA-scan and bisphosphonates use indicate we can improve prevention of bone loss.