The following question was addressed by Joanne Kotsopoulos, PhD, who is a scientist at Women’s College Hospital in Toronto, Canada, with a longstanding interest in researching hormonal and other risk factors among those with inherited forms of breast cancer.
Q:What is the latest information about risks of taking hormone replacement therapy (HRT) in BRCA1/2 carriers without a past diagnosis of breast cancer?
A: The information we have is reassuring that HRT does not further raise the risks of breast cancer in pre-menopausal BRCA1/2 carriers following risk-reducing salpingo-oophorectomy. We recently published a study among BRCA1/2 carriers without a prior breast cancer diagnosis (which included ICARE participants) and showed that HRT use (either estrogen plus progesterone OR estrogen alone) did NOT lead to a significant increase in
breast cancer risk and that estrogen alone HRT may actually be protective (meaning this may actually lower risk).1 Findings were similar regardless of the type of estrogen or how the HRT was given (whether it was oral, injected, or absorbed through the skin). It is important to remember that estrogen alone is not given in someone who has their uterus, as it can then raise the risk of uterine (also referred to as endometrial) cancer. This is important information for women with BRCA1/2 mutations as well as their healthcare providers. Given their high risk of ovarian (or fallopian tube) cancer, these women are strongly encouraged to remove their ovaries and tubes at an early age leading to early surgical menopause. HRT is the most effective way to mitigate the health issues that go along with early menopause that may include vasomotor symptoms, a decline in quality of life and other side effects. Importantly, this study shows that HRT can be used safely in this population. Prior research studies have also shown that among BRCA carriers without a history of breast cancer, HRT does not further raise the risk for breast cancer.2-5
1Kotsopoulos, et al. J Natl Cancer Inst. 2025:djaf363. PMID: 41403285.
Article available at: https://pubmed.ncbi.nlm.nih.gov/41403285/
2Rebbeck, et al. J Clin Oncol. 2005;23(31):7804-10. PMID:16219936.
Article available at: https://pubmed.ncbi.nlm.nih.gov/16219936/
3Eisen, et al. J Natl Cancer Inst. 2008;100(19):1361-7. PMID:18812548.
Article available at: https://pubmed.ncbi.nlm.nih.gov/18812548/
4Kotsopoulos, et al. Breast Cancer Res Treat. 2016;155(2):365-73. PMID:26780555.
Article available at: https://pubmed.ncbi.nlm.nih.gov/26780555/
5Mills KA, et al. Gynecol Oncol. 2020 Jun;157(3):706-710. PMID: 32143914.
Article available at: https://pubmed.ncbi.nlm.nih.gov/32143914/