A prospective study of 872 BRCA1 PV carriers of whom 43% (77% premenopausal, 23% postmenopausal at RRSO, mean age 43 years, range 30–70 years) took HRT for a mean of 3.9 years (range 0.5–19 years) concluded that estrogen alone did not increase breast cancer risk but the safety of progestin-containing HRT was uncertain.25 A 2019 systematic review including seven studies (n = 933 BRCA1/2 PV carriers) concluded that HRT could be used for up to 4.3 years without increasing breast cancer risk.26 Age at initiation of HRT may be important. The gene discussed is BRCA1; the disease is breast cancer.