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Does Hormone Replacement Therapy After Oophorectomy Affect Breast Cancer Risk in BRCA1-Mutation Carriers?

By: Sarah Campen, PharmD
Posted: Tuesday, July 24, 2018

The use of any hormone replacement therapy in BRCA1-mutation carriers after oophorectomy for the prevention of ovarian cancer does not seem to be associated with an increased risk of breast cancer, although a nonsignificant increase in risk was observed with progesterone-containing hormone replacement therapy. Joanne Kotsopoulos, PhD, of the Women’s College Research Institute in Toronto, Canada, and colleagues also identified a possible protective effect from the development of breast cancer for women who used estrogen-containing hormone replacement therapy. The results of the prospective, longitudinal cohort study were published in JAMA Oncology.

“Our findings indicate the BRCA1 mutation carriers should not avoid risk-reducing surgery because of the fear associated with estrogen-alone [hormone replacement therapy] use,” stated the researchers.

They enrolled 872 BRCA1-mutation carriers who had undergone oophorectomy, and 377 of those women received hormone replacement therapy. Breast cancer was diagnosed in 92 of the women (10.6%) during the follow-up period.

Each year of estrogen use was associated with an 8% reduction in breast cancer risk (P = .07), whereas each year of progesterone use was associated with an 8% increased risk (P = .34). After 10 years of follow-up, the cumulative incidence of breast cancer among women who used estrogen-alone hormone replacement therapy was significantly lower at 12%, compared with 22% among women who used estrogen plus progesterone hormone replacement therapy (P = 0.4). Researchers cautioned that “the possible adverse effect of progesterone-containing [hormone replacement therapy] warrants further study.”

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