A drug that new mothers sometimes take for a simple reason, to dry up breast milk they no longer need, may come with an unexpected second payoff: sharply lower odds of breast cancer in the years after childbirth. In a combined analysis of two large European studies, women who received cabergoline shortly after giving birth were about 69% less likely to develop breast cancer than women who didn’t.
Breast cancer that shows up in the years right after pregnancy tends to be more aggressive and harder to treat than cancer diagnosed at other times. Scientists have long known that having a baby early offers long-term protection against breast cancer, but the months right after childbirth actually bring a temporary spike in risk, one that hits hardest for women who had their first child later in life or who carry BRCA1 gene mutations. Until now, no specific method has protected those women during that dangerous stretch.
Researchers from institutions in Spain, Canada, Norway, the United Kingdom, Singapore and the United States, reporting in the journal Cancer Discovery, tested whether cabergoline, already approved to stop lactation, could close that gap. In mice bred to carry a high-risk breast cancer mutation, a single dose of the drug given right after weaning sharply delayed and reduced tumors, a clue that helped explain the pattern researchers later found in women.
How a Single Dose of Cabergoline Cut Breast Cancer in Mice
To test the idea, researchers used mice bred without working copies of two genes that normally guard against cancer: BRCA1 and a second gene called Trp53. Female mice that went through two full rounds of pregnancy, breastfeeding, and the natural recovery period afterward developed tumors later, and less often, than mice that never had pups at all. Tumors appeared around day 224 in mice that had given birth, compared with day 175 in mice that hadn’t. Only 59% of the mothers developed tumors, versus nearly 89% of the childless mice.
Then the team gave a single dose of cabergoline to another group of mother mice right when breastfeeding ended. Tumors took even longer to appear, around 259 days, and only about 28% of treated mice developed tumors. Giving the same drug to mice that had never been pregnant did almost nothing to protect them, which told researchers the benefit was tied specifically to the recovery window after breastfeeding, not some general cancer-fighting effect.
So what’s actually happening inside the breast tissue during that window? After a mother stops nursing, the breast naturally shrinks back down, clearing out the milk-producing cells it no longer needs. In mice carrying the cancer-linked gene mutations, that cleanup process slowed and left behind riskier tissue, including cells with two nuclei instead of one, which are especially prone to becoming cancerous when their normal damage-control systems are broken. Cabergoline noticeably sped up that cleanup: treated breast tissue shrank faster, had fewer risky double-nuclei cells, and showed less overall tissue growth two months later.
Cabergoline also seemed to help the immune system. Breast tissue from the high-risk mice showed signs that T cells, the immune cells that normally hunt down and destroy abnormal cells, had become worn out and less effective. Cabergoline appeared to reverse that pattern. Treated tissue had more active, cancer-fighting T cells and fewer that showed signs of exhaustion. Researchers believe the combination, healthier tissue plus a stronger immune response, helps explain why treated mice developed far fewer tumors.
What Cabergoline Means for Breast Cancer in Real Women
To see whether any of this held up outside the lab, researchers examined medical records from two different European populations. The first came from a primary care database in Catalonia, Spain, covering more than 14,800 women who had their first child at age 30 or older. Of those, 780 had received cabergoline within a month of giving birth. Over an average of eight years of follow-up, only 2 of those 780 women developed breast cancer, compared to 132 cases among the more than 14,000 women who hadn’t taken the drug. After accounting for other risk factors like age, smoking, family history and income, women who’d taken cabergoline still showed roughly a 75% lower risk of developing breast cancer.
A second analysis using the same Spanish database, this time looking at all women within ten years of their first pregnancy regardless of age, told a similar story: 2 cancer cases among 1,604 treated women, compared to 125 cases among nearly 26,000 untreated women.
To make sure the pattern wasn’t unique to one country, researchers checked it against a nationwide registry in Norway covering more than 690,000 women. The results pointed in the same protective direction, though the small number of cancer cases there, 2 among treated women compared to 899 among untreated women, meant the finding didn’t clear the usual bar scientists use to call a result reliable on its own. When the team combined the data from both countries, the pooled analysis showed an estimated 69% reduction in breast cancer risk linked to cabergoline use after childbirth.
Source : https://studyfinds.com/common-lactation-drug-linked-to-sharply-lower-breast-cancer-risk/