An international team of researchers has identified that cabergoline—a drug used to halt the production of breast milk—may reduce the risk of breast cancer when administered at the end of the lactation period. The findings, published this Thursday in the journal Cancer Discovery, combine evidence from animal models with an analysis of the medical records of more than 150,000 women in Spain and Norway.

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The research involved scientists from several countries, including specialists from the Cancer Research Center in Salamanca—a joint facility of the University of Salamanca and the Spanish National Research Council (CSIC).

In studies involving mice, the researchers found that a dose of cabergoline administered at the end of lactation reduced the proportion of animals that developed breast cancer by approximately half. The models used carried mutations in the BRCA1 and TP53 genes, which are linked to DNA repair, the elimination of damaged cells, and aggressive forms of the disease.

According to the team, the drug reduced potentially precancerous tissue, decreased the ductal area, inhibited cell growth, and increased the presence of immune cells involved in defending against tumors.

The study focuses on mammary involution—the natural “clearing” process that occurs after weaning. During pregnancy, hormone levels rise and milk-producing structures branch out; once lactation ends, these cells are no longer needed, and the breast eliminates the excess tissue.

“It’s like a fruit tree; in spring and summer, the breast develops branches and produces flowers and fruit, but when involution occurs—which is the mammary equivalent of winter—the structures required for pregnancy and lactation are reset in preparation for the future,” explained Christopher Maxwell, a professor at the University of British Columbia’s Faculty of Medicine in Canada and a researcher at the BC Children’s Hospital Research Institute.

💊Un fármaco podría reducir el riesgo de #CáncerDeMama postparto

🔬Cabergolina se receta para frenar la lactancia tras el parto

👩‍🔬@ciccancer muestra en ratones que reduce los tumores

🔎Un ensayo evaluará su eficacia en mujeres tras dejar de amamantar
➡️https://t.co/FqTffmBrvm pic.twitter.com/AahOcNLZyX

— CSIC (@CSIC) October 15, 2026

The text reads, “A drug could reduce the risk of #BreastCancer postpartum. Cabergoline is prescribed to halt breastfeeding after childbirth. @ciccancer shows in mice that it reduces tumors. A trial will evaluate its efficacy in women after stopping breastfeeding”

The researchers discovered that in mice with mutations in the BRCA1 and TP53 genes, this cleanup process can remain incomplete. In such cases, cabergoline appears to help complete the involution process following weaning.

To explore the effect in humans, the team reviewed medical records from Spain and Norway, focusing specifically on young women in the years following pregnancy. In total, the studies included data on the use of cabergoline in more than 150,000 women.

The results showed that women who received the drug to suppress lactation after childbirth—whether due to a medical recommendation, following the loss of a pregnancy, or because breastfeeding was not possible for medical reasons—had an approximately 70 percent lower risk of developing breast cancer compared to those who did not take it.

This association was observed in women under the age of 50 during the years following pregnancy—a period when the risk of this disease can increase.

Cabergoline is a prescription medication used only when medically necessary to stop milk production. It is not currently approved for the prevention of breast cancer; therefore, the authors emphasize that these findings should not be interpreted as a recommendation for its use as a preventive measure.

The next step will be a prospective clinical trial involving women who will receive the drug only after breastfeeding has ended. The goal is to determine whether cabergoline might, in the future, offer a less aggressive alternative to current preventive measures against breast cancer, such as surgery or hormone therapy.

#Science | A new Science special feature is putting the spotlight on major gaps in women’s health research beyond reproduction, from chronic pain and menopause to sex chromosomes and the immune system.

Researchers say significant gaps remain in understanding how diseases affect… pic.twitter.com/NXoaaRa3h5

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