Small, preclinical studies on breast tissue suggest the pill mifepristone shows promise for reducing the risk of breast cancer, however the use of mifepristone for medical abortion has created barriers for developing it for other purposes. This finding is highlighted in a Viewpoint published in The Lancet Obstetrics, Gynecology, & Women’s Health.

Globally, breast cancer is the leading cause of cancer deaths among women. For women at high risk of breast cancer, for example with a BRCA mutation, the current risk-reducing strategies are surgery or estrogen receptor medications, which often have unwanted side effects. There is an urgent need for alternative and non-surgical risk-reducing options to prevent breast cancer.

Three small laboratory studies have found mifepristone can slow down cell growth in breast tissue, including in breast tissue from women with a BRCA mutation. This is due to mifepristone inhibiting the effects of the hormone progesterone, a driver of cell growth. However, large preclinical and early-phase clinical studies are needed to evaluate the safety and efficacy of mifepristone specifically in the context of breast cancer prevention.

The authors highlight the unwillingness of pharmaceutical companies to be associated with mifepristone, as well as countries with restricted abortion access limiting the availability of the medication. They argue that funding bodies and the pharmaceutical industry have too long delayed supporting research into mifepristone as a non-surgical breast cancer prevention option and call for backing from policy-makers and governments.