Diabetes Drug Linked to 35% Drop in Breast Cancer Risk

Medications designed to treat diabetes and obesity might be doing something remarkable that nobody planned for: protecting women from breast cancer.

A major study published today in JCO Oncology Practice examined health records from nearly 112,000 women between ages 45 and 80. Researchers discovered that women taking GLP-1 medications like Ozempic and Zepbound were 35% less likely to develop breast cancer compared to those not on the drugs.

The team at the Hospital of the University of Pennsylvania tracked women with a BMI of 25 or higher who underwent breast imaging between January 2022 and June 2025. Of the participants, about 14% had prescriptions for GLP-1 medications while the rest did not.

To make sure the results held up, researchers created a smaller comparison group where they matched women on GLP-1s with similar women who weren't taking them. They controlled for age, race, BMI, and other health factors. Even in this tightly controlled group, the breast cancer risk dropped by 30%.

The link isn't totally random, according to oncologists. After menopause, body fat becomes a woman's main source of estrogen, and estrogen fuels the most common type of breast cancer. When GLP-1s help people lose weight, estrogen levels drop too.

There's more happening beyond weight loss. These medications also lower insulin and a growth signal called IGF-1, both of which can encourage tumors to grow. They also reduce the chronic inflammation that comes with carrying extra weight.

Dr. Gilberto Lopes, chief of Medical Oncology at the University of Miami Health System, points out that some breast tumors even carry GLP-1 receptors on their surface. This suggests the drugs might directly impact cancer cells themselves.

Why This Inspires

This research opens a door that could change how we think about breast cancer prevention. We already use medications like tamoxifen to help high-risk women lower their odds of developing the disease. GLP-1s could become another tool in that prevention toolbox.

The timing matters too. Breast cancer remains one of the most common cancers affecting women, and obesity rates continue climbing. A medication that addresses both metabolic health and cancer risk could help millions of women simultaneously tackle two major health challenges.

Dr. Elizabeth McDonald, the study's lead author, emphasizes that while these findings are observational, they're significant enough to warrant immediate further research. The possibility that a widely available medication might offer protection against breast cancer represents genuine hope for preventive medicine.

For now, doctors say GLP-1s for cancer prevention probably make the most sense for women who have both elevated breast cancer risk and health reasons to lose weight. More research will determine whether the benefits extend to women at healthy weights, but the initial signal is lighting up screens in oncology departments across the country.