A new study has revealed that GLP-1 drugs, widely used to treat obesity and type 2 diabetes, may be associated with a reduction in the likelihood of developing breast cancer by up to 30%.
The study, whose results were presented at the 2026 American Society of Clinical Oncology Annual Meeting and published in the journal JCO Oncology Practice, included more than 110,000 women.
The researchers found that women who took GLP-1 drugs were 35.1% less likely to develop breast cancer compared to all participants in the study, and the percentage dropped to 30.5% when each drug user was compared to a non-user woman similar to her in age, weight, breast density, and diabetes status.
Dr. Elizabeth MacDonald, professor of radiology at the University of Pennsylvania and lead author of the study, explained that these findings, although observational and not conclusive, add to the growing evidence of the importance of studying these drugs as options for cancer prevention.
GLP-1 drugs work by mimicking a natural hormone that regulates blood sugar and appetite. Although they were originally developed to treat diabetes, their use has expanded to include weight loss. Previous studies have suggested they are associated with a reduced risk of cancer or improved outcomes for survivors, but future clinical trials that provide stronger evidence have not yet been completed.
Researchers believe that the explanation for this association may be due to several factors, including the effectiveness of the drugs in reducing weight, as excess weight is known to be a risk factor for breast cancer, especially after menopause, as well as their ability to reduce chronic low-grade inflammation, which is a contributing factor in cancer development, in addition to their potential metabolic and genetic effects that may slow tumor growth.o
The analysis did not address the differences between the various types of GLP-1 drugs, the duration of treatment, genetic factors, or the stage of cancer at diagnosis, prompting the team to plan additional studies to explore these aspects.
McDonald's team is currently preparing to launch a multi-site clinical trial to confirm these results, especially in high-risk women such as breast cancer survivors or those carrying gene mutations, as prevention options are currently limited. Some resort to prophylactic mastectomy, while others avoid the drug tamoxifen due to its side effects, making GLP-1 drugs an attractive option if their effectiveness is proven in clinical trials.
MacDonald hopes these findings will contribute to improved prevention options, noting that breast cancer survival rates have improved in recent decades, and that progress in prevention may be the logical next step.
