Multicenter retrospective cohort study of hormone therapy and breast cancer risk in women with BRCA pathogenic variants

The use of hormone replacement therapy (HRT) after risk-reducing bilateral oophorectomy (RRBO) in women carrying BRCA1/2 pathogenic variants (PVs) remains debated due to concerns about its possible role in breast cancer (BC) risk. A retrospective cohort study at 3 centers in Israel assessed the possible association between HRT use and BC incidence after RRBO in women harboring a limited range of germline BRCA PVs. A total of 919 adult women (mean age at RRBO 47.6 ± 8.9 years; 496 with BRCA1 PV; 423 with BRCA2 PV) were included . During a mean follow-up of 8.8 ± 6.2 years, 144 women (16%) were diagnosed with invasive BC. Overall,381 participants (42%) had ever used and 538 (58%) had never used HRT following RRBO. Ever use of HRT was not associated with increased BC risk (combined estrogen-progestin: HR 1.06; 95% CI 0.67-1.68; estrogen only: HR 0.89; 95% CI 0.48-1.63). In duration of use analyses, each year of estrogen-only HRT was associated with a reduction of BC risk (HR 0.90; 95% CI 0.81-0.99). The authors conclude that HRT use was not associated with increased BC risk after RRBO among women with BRCA1/2 PVs.