An international research team, composed of researchers from the Cancer Research Center (CSIC, University of Salamanca, FICUS) and IBSAL, has discovered that cabergoline, a medication used to suppress lactation, may reduce the risk of breast cancer.
This is a promising approach that, if successful in upcoming clinical trials, could be used as a preventive strategy, offering a gentler treatment option for women who need it.
An international research team, made up of researchers from the Cancer Research Center (CSIC, University of Salamanca, FICUS) and IBSAL, has discovered that a medication used to suppress lactation may reduce the risk of breast cancer in mothers after childbirth. The drug cabergoline suppresses milk production and is prescribed following a pregnancy loss or when breastfeeding is not possible. Currently, cabergoline is not approved for the prevention of breast cancer.
The study, published in *Cancer Discovery*, analyzed medical records from Spain and Norway, including more than 150,000 women with recorded information on whether or not they had used cabergoline. The analysis revealed an association: women who took cabergoline to suppress milk production after childbirth had approximately a 70% lower risk of developing breast cancer in the following years, compared with those who did not receive the medication.
This finding was consistent with what the team observed in mice. They tested a single dose of cabergoline at the end of the lactation period in mice carrying mutations in the BRCA1 and TP53 genes—which are associated with aggressive forms of breast cancer—and the percentage of mice that developed breast cancer was reduced by approximately half.
“Breast cancer is the leading cause of cancer death among young women, and most of these cases occur in the years following pregnancy. This is especially true for women at high risk of developing breast cancer,” says the study’s co-director, Dr. Christopher Maxwell, a professor at the University of British Columbia (Canada) School of Medicine and a researcher at the British Columbia Children’s Hospital Research Institute. “Our findings suggest that it may be possible to reduce that risk by helping the breast complete a natural process that occurs after breastfeeding has stopped.”
Like a fruit tree preparing for winter
When a woman stops breastfeeding, the breast undergoes a significant cleansing process called involution. Dr. Maxwell compared it to a fruit tree. In the spring and summer, the tree grows branches and produces flowers and, eventually, fruit. Once the fruit has disappeared, the tree sheds what it no longer needs and prepares for the next season.
Similarly, during pregnancy, hormone levels rise and the milk-producing structures in the breast branch out, creating a “ductal tree.” However, once breastfeeding ends, those cells are no longer needed, and the breast undergoes involution to eliminate the excess tissue.
“We believe that involution is the mammary equivalent of winter,” said Dr. Maxwell. “It is a period during which the structures that were necessary for pregnancy and lactation are reset for the future.”
However, researchers have discovered that this cleanup process may be incomplete in laboratory mice, leaving behind cells that could become cancerous.
Cabergoline appears to help complete this transition by accelerating the breast’s natural process following weaning. In studies with mice, it reduced potentially precancerous tissue, decreased the ductal area, reduced cell growth, and increased the presence in the breast of immune cells involved in defending against tumors.
Clinical Trial Planning
“We believe that the post-breastfeeding period is an important window of opportunity for prevention. There is a unique opportunity to intervene in involution, the natural process that begins after weaning. This is not about changing women’s breastfeeding plans; any preventive intervention would only be considered once breastfeeding has ended,” says Dr. Jesús Pérez-Losada, a CSIC researcher at the CIC and IBSAL and co-director of the study. “Cabergoline still needs to undergo prospective trials. Therefore, the next step is to test it in clinical trials and determine whether the benefits we have observed can be confirmed in women.”
The multinational research team has already secured funding from the Gray Foundation for a clinical trial targeting women with a BRCA1 gene mutation.
Participants will be recruited through clinics specializing in high-risk pregnancies and will choose how long they wish to breastfeed. After weaning, they will receive cabergoline or a placebo, while the research team monitors biological markers related to future breast cancer risk.
If it proves successful in upcoming clinical trials, the drug’s existing approval for another use could accelerate its development as a preventive strategy, offering a gentler treatment option for women who need it.
This research was funded by the Canadian Institutes of Health Research, the Canadian Cancer Society, the Terry Fox Research Institute, and the Ministry of Science, Innovation, and Universities through the Spanish National Research Agency, with additional support from funding agencies in the United Kingdom and the United States, as well as the We Can Be Heroes Association.
Study Reference
García-Sancha N, Corchado-Cobos R, Ghorayeb R, et al. Cabergoline Suppresses Postpartum Breast Cancer by Enhancing Mammary Gland Involution in BRCA1-Mutant Mice and Is Associated with a Reduced Risk in Younger Women. Cancer Discovery. DOI: 10.1158/2159-8290.CD-26-0187.
Contact
Almudena Timón. Head of Communications, CIC
923 294 720
