Observational Study Links GLP-1 Use to 30% Lower Breast Cancer Rate, but Researchers Caution Findings Are Not Definitive

A study published in the JCO Oncology Practice journal examined University of Pennsylvania Health System records from more than 111,000 women ages 45 to 80 who were overweight or obese. Researchers tracked which of those women developed breast cancer over the last several years.

Women taking GLP-1 medications showed a reduced risk of developing breast cancer by about 30 percent, according to the analysis.

The study's lead author and a professor of radiology at the University of Pennsylvania Perelman School of Medicine, said the findings were observational. McDonald stated that the results do not definitively confirm an association between GLP-1 medications and reduced breast cancer incidence.

She added that the study contributes to evidence suggesting the drugs merit investigation as potential cancer prevention tools.

Dr. Tara Narula discussed the study on Good Morning America on Wednesday. She said the research is hypothesis-generating and not practice-changing. Narula noted that after menopause, fat cells produce estrogen and that higher estrogen levels can increase breast cancer risk.

She also pointed to obesity as a pro-inflammatory state linked to elevated cancer risks and higher insulin levels that can drive some cancers. Narula said the mechanisms of GLP-1 medications—reducing weight, lowering inflammation, and improving insulin sensitivity—could plausibly affect breast cancer risk.

Some evidence indicates GLP-1 medications may directly reduce tumor growth and slow metastatic progression, Narula said.

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