Dr. Elizabeth McDonald’s study on GLP-1 drugs and breast cancer risk, published June 2 in JCO Oncology Practice, found that women taking weight-loss medications like Ozempic had a 35% lower risk of developing breast cancer, with the effect persisting after matching participants for age, BMI, and other factors.
Dr. Elizabeth McDonald’s Findings
Dr. Elizabeth McDonald, a professor of radiology at the University of Pennsylvania Perelman School of Medicine, led a study analyzing health records of 112,000 women aged 45 to 80 with a BMI of 25 or higher. The research, presented at the American Society of Clinical Oncology’s annual meeting, revealed that women prescribed GLP-1 drugs—such as Ozempic and Zepbound—had a 35% lower risk of breast cancer compared to those not taking the medications. After matching GLP-1 users with non-users for demographic and health factors, the risk reduction narrowed to 31%, still significant according to U.S. News & World Report.
“While our study was observational and does not definitively confirm an association between GLP-1 medications and reduced breast cancer incidence, it does add to the growing body of evidence suggesting that it’s worth investigating these weight-loss drugs as potential cancer prevention tools,” McDonald said, emphasizing the need for further clinical trials per The Guardian.
Observational Evidence and Cautious Optimism
The study’s findings align with a broader trend of research linking GLP-1 drugs to cancer risk reduction. A separate analysis presented at the same oncology conference found that GLP-1 users had a 30% lower risk of breast cancer mortality, while another study reported a 50% reduction in cancer spread among patients with breast, lung, bowel, or liver cancer The Guardian. However, researchers stress that the studies are observational and do not prove causation.
“These results should only increase the possibility there’s a real biological signal that should be studied in a robust clinical trial,” McDonald said, noting that GLP-1 drugs’ anti-inflammatory properties and weight-loss effects may contribute to their potential cancer-protective role per USA Today.
Mechanisms Behind the Risk Reduction
GLP-1 drugs, originally developed to treat type 2 diabetes, work by mimicking the hormone glucagon-like peptide-1, which regulates blood sugar and appetite. Their weight-loss effects are well-documented, and obesity is a known risk factor for postmenopausal breast cancer. By helping patients lose weight, GLP-1 drugs may indirectly lower cancer risk The Washington Post.
However, the drugs’ impact extends beyond weight loss. McDonald highlighted that GLP-1s reduce systemic inflammation and may influence metabolic and epigenetic pathways linked to cancer development. “GLP-1 medications are intriguing from a cancer research perspective because they weren’t designed for cancer therapy, but they do affect many different targets and pathways associated with cancer development,” she said The Guardian.
Limitations and Future Research
While the findings are promising, the studies have limitations. The research relied on health records from Penn Medicine, excluding patients who obtained GLP-1 drugs through telehealth or compounding pharmacies. Additionally, the studies did not account for genetic risk factors or cancer stage at diagnosis USA Today.
“The benefits would be transformative for women’s health,” McDonald said, urging further research to confirm the findings. “Ultimately, we want to find better options to prevent breast cancer. It’s been encouraging to see the survival rates for breast cancer improve over recent decades, and we’d love to see the same gains in prevention,” she added U.S. News & World Report.
What Comes Next?
The next step is to design randomized controlled trials to establish whether GLP-1 drugs can be repurposed as cancer prevention tools. Researchers also aim to identify which patient populations might benefit most and whether the drugs’ effects vary by cancer type. If confirmed, GLP-1s could offer a new strategy for reducing breast cancer risk, particularly for overweight individuals.
“This is a critical moment in cancer research,” said McDonald. “The potential for these drugs to impact prevention is immense, but we must proceed with scientific rigor to ensure safety and efficacy.”
