There is growing evidence to suggest that common weight loss drugs, such as Ozempic and Mounjaro, could have a protective effect against developing breast cancer and may even help delay progression — and improve survival odds — in those already diagnosed with the disease.
One study published in the Journal of Oncology and presented at this year’s ASCO (American Society of Clinical Oncology) annual meeting found patients taking GLP-1 agonists were almost a third less likely to develop breast cancer than their peers.
Still, while several new studies offer promising hints at the medication’s potential, the results show a correlational link, not a causal link. While it is too early to make any definitive claims, researchers say it warrants further investigation.
“These findings support the need for prospective trials investigating incretin medications for breast cancer prevention,” the study authors wrote.
GLP-1 Agonists and Cancer Diagnosis
A team of researchers at the University of Pennsylvania and American College of Radiology scoured the electronic health records of over 94,000 patients for a retrospective study — a technical term meaning the researchers examined historical data to identify any patterns between past exposures and outcomes.
In this case, the scientists looked at records collected between Jan. 1, 2022, and June 30, 2025, to determine any links between GLP-1 use (past exposure) and a breast cancer diagnosis (outcome).
All participants included in the study were females aged 45 to 80 years with a BMI of 25 or more. In total, 15,107 (or 15.9 percent) had been exposed to GLP-1 agonists, meaning they received their first prescription before undergoing breast imaging. The remaining 79,720 (84.1 percent), who had not, served as the control group.
Just over 2,300 participants (2.4 percent) were diagnosed with breast cancer over the course of the study, but there was a significant difference between the two groups. Of those exposed to GLP-1s, 249 (1.65 percent) were diagnosed with breast cancer compared to 2,065 (2.6 percent) of the control group. In relative terms, that is a difference of more than a third.
Read More: GLP-1 Weight Loss Drugs May Increase Brain Connectivity — and Faster Than Expected
Results Hold Up During Case-Control Matching
To dig a little deeper and negate the effect of any confounding variables — third-party factors that can unhelpfully influence the final results — the team completed one-to-one, case-control matching. This meant the researchers could directly compare patients who were similar in terms of their age, race, ethnicity, BMI, and breast density, as well as their type-2 diabetes status.
This exercise involved more than 30,000 observations and 580 cancer cases. Again, they found GLP-1 exposure was linked to a lower incidence of breast cancer, though the difference was not quite as stark as before. The rate of breast cancer in GLP-1 users was 1.65 percent versus 2.2 percent in non-GLP-1 users.
It is important to note that neither case shows that taking GLP-1s directly reduces the likelihood of developing breast cancer — it simply shows a correlation the researchers believe is worth investigating. The study is also limited to a subset of society, namely women aged 45 to 80 with a BMI of 25 or more.
GLP-1 Agonists and Cancer Progression
A second study, also published in the Journal of Oncology, again looked at GLP-1 use and cancer. This time in those already diagnosed with the disease.
In total, the researchers tracked the progression of disease in more than 10,000 people diagnosed with stage I to III cancer. The study wasn’t strictly restricted to breast cancer, but it was one of seven types included in the research.
The results suggest GLP-1 use reduces the rate of progression of six of the seven cancers studied, including breast cancer. In patients who were prescribed the weight loss drug after diagnosis, approximately 10 percent of breast cancers progressed to stage IV. In contrast, those who were prescribed gliptins (or DPP-4 inhibitors) — a medication also taken to manage diabetes — 20 percent of breast cancers progressed to stage IV.
The researchers also note data in The Cancer Genome Atlas suggests a 45 percent reduced risk of death in breast cancer patients who took GLP-1s.
“GLP-1 receptor agonists have never been just glucose-lowering drugs. Their anti-inflammatory and immune-modulatory properties have long suggested broader effects,” Marcin Chwistek, M.D., FAAHPM, chief of Supportive Oncology and Palliative Care Program at Fox Chase Cancer Center and an ASCO expert in supportive care, said in a statement. “What's new here is the consistency across tumor types, and data this large and this consistent warrant a prospective randomized trial.”
This article is not offering medical advice and should be used for informational purposes only.
Read More: GLP-1 Drugs May Cut Risk of Heart Attack, Stroke, and Death by About 13 Percent
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from the Journal of Oncology: Association of GLP-1 agonists with breast cancer incidence in women
- This article references information from the Journal of Oncology: Can GLP-1 receptor agonists mitigate cancer progression? A propensity-matched analysis across seven solid tumors
