New research seems to link the use of GLP-1 (Ozempic, Wegovy, and Zepbound) with better breast cancer outcomes. Scientists don't yet know why this is — it may not be the medications themselves, but rather the improved inflammation, body fat, and insulin resistance that GLP-1s can help with.
While it's too soon to start prescribing GLP-1s for breast cancer prevention and treatment, here's why people are talking about it.
Is There a Link Between GLP-1s and Breast Cancer Risk?
Two 2026 studies suggest there could be a connection between taking GLP-1 drugs and breast cancer risk and outcomes.
In a study published in June in the journal JCO Oncology Practice, researchers looked at the medical records of 217,624 overweight women ages 45-80 who had a mammogram between 2022 and 2025. Regardless of other risk factors for breast cancer, such as age, race, ethnicity, weight, breast density, and diabetes, women who were taking GLP-1s were less likely to be diagnosed with breast cancer during the selected time period.
Another study, presented this year at the American Society of Clinical Oncology Annual Meeting, looked at the medical records of 2,374 people with stage I-III breast cancer. Researchers paired the people with shared factors that might affect their risk of progression to stage IV metastatic disease, including demographics, body mass index (BMI), diabetes, smoking, other illnesses, screening frequency, treatment type, and other medications they were taking. One member of the pair had started a GLP-1 after diagnosis. The other had started with a different diabetes drug class called DPP-4 inhibitors (gliptins). While the members of each pair were similar in many other ways, those taking GLP-1s were less likely than those taking gliptins to progress to metastatic breast cancer.
But these studies don't prove that GLP-1 drugs themselves produced either benefit.
"We can conclude: GLP-1 use is associated with lower breast cancer incidence," says Christina M. Dieli-Conwright, PhD, MPH, an associate professor at Dana-Farber Cancer Institute in Boston. "We cannot conclude: GLP-1 drugs prevent breast cancer. That requires randomized controlled trials."
How do you prove it was the GLP-1s?
These studies were retrospective observational studies. That means they look back at a group of people who have already chosen to take the drug being studied. These types of studies can't totally rule out other causes of the end result.
Prospective randomized controlled clinical trials are designed to find out whether a medication causes a specific outcome. For this type of study to prove that GLP-1s directly lower breast cancer risk, a large group of women who are overweight and share other similar risk factors for breast cancer would be randomly assigned to either take a GLP-1 for weight loss or to lose weight by some other method.
The researchers would keep track of all the people in the study for several years. At the end of the designated time period, say 10 years, the researchers would compare the breast cancer rates of those who successfully lost weight with a GLP-1 to those who successfully lost weight in another way. If the GLP-1 group had lower breast cancer rates than women who lost the same amount of weight in another way, that would suggest the drugs themselves prevented cancer.
Why Would a Diabetes and Weight Loss Drug Affect Breast Cancer Risk?
Women who are overweight have a higher risk of breast cancer, and GLP-1s help you lose weight. That may explain much of it, but there's more to unpack here.
The obesity-breast cancer connection
Overweight and obesity cause multiple changes in the body that may make conditions ripe for breast cancer development.
Too much fat can cause ongoing, low-grade inflammation throughout the body. Inflammation on its own can cause changes that may eventually lead to the development of cancer. It may also make the immune system less able to fight cancer.
When the immune system isn't running as it should, it may not be able to monitor for abnormal cells that could eventually become cancerous. If you already have cancer, immune system dysfunction caused by obesity may also prevent cancer treatments from working as well as they should.
Finally, overweight and obesity can lead to insulin resistance. Insulin is the hormone produced by the pancreas that the body needs to process sugar. When the cells become resistant to insulin, the pancreas cranks out more.
Insulin not only helps regulate blood sugar, but it also sends signals that encourage cells to grow and divide. Too much cell growth and division — in this case caused by too much insulin — can produce and proliferate cancerous cells.
High insulin and insulin-related growth signals add "fuel to the fire for an altered cell and tumor development," says Stephen Hursting, PhD, AICR/WCRF distinguished professor of nutrition and cancer at UNC Chapel Hill Lineberger Comprehensive Cancer Center.
How GLP-1 drugs might help
Any reduction in breast cancer risk seen in GLP-1 users is currently believed to be the result of weight loss. Losing weight begins to reverse the systemwide dysfunction, such as insulin resistance, chronic inflammation, and immune system dysregulation, that overweight and obesity can cause.
There's not enough evidence to suggest a direct effect of the drugs themselves on either existing cancer cells or the process of developing cancer. But that doesn't mean researchers have ruled it out.
Research in mice led by Erika Crosby, PhD, at Duke University School of Medicine, finds that GLP-1-induced weight loss doesn't just drive cancer risk back down to the risk of a lean mouse; it drives risk lower than that.
"We see not just a reversal of the obesity effect, but actually a protective effect. We may be able to go beyond just reversing the problem," says Crosby, who is an assistant professor in integrative immunobiology.
But other mouse studies contradict that finding. Hursting's research, for example, shows that extreme calorie reduction, with or without the help of GLP-1s, had the same effect on cancer risk in mice.
"I think this tells us that much of the effect is through weight loss, decreased appetite, and adipose [fat] loss," he says.
His research also found that administering GLP-1s directly to cancer cells in a petri dish had no benefit.
More study is needed to find the true mechanism at work, experts say.
Should I Start or Keep Taking a GLP-1 to Prevent Breast Cancer?
It's just too soon to label GLP-1s as cancer prevention therapy. While the new studies show a link between GLP-1 use and a lower risk of breast cancer, there haven't yet been randomized controlled trials to prove that the medications themselves prevent breast cancer. But staying at a healthy weight does lower the risk of breast cancer, and these drugs may help you do that.
If you have concerns about your individual breast cancer risk and the role that a GLP-1 drug might play in lowering your risk, discuss this research and your unique breast cancer risk factors with your doctor.
What if You've Already Had Breast Cancer?
Just as staying at a healthy weight can help prevent breast cancer to begin with, it can also help stop it from coming back. In that respect, GLP-1s could help people lose weight and lower their risk of recurrence.
But when you're a breast cancer survivor, there's a lot more to consider before starting a GLP-1 for weight loss.
If you're still in treatment, you should talk to your cancer care team before starting a GLP-1. These weight loss drugs can slow the movement of oral medications through the gut, which could affect how the drugs work. It's not known whether GLP-1s interact with other non-oral cancer medications. Some of the side effects of GLP-1s might also be too much to add on top of any side effects you're having from your cancer treatment.
For people who have already completed breast cancer treatment, GLP-1s are considered safe when taken for the approved conditions: type 2 diabetes or obesity.
"There is no evidence that GLP-1RAs increase the risk of breast cancer recurrence or new primary breast cancers," Dieli-Conwright says.
But you shouldn't take them with the purpose of preventing a recurrence.
Takeaways
New research finds a connection between GLP-1 use and a lower risk of breast cancer and breast cancer metastasis. But the studies don't prove whether it was the drugs themselves that lowered these risks or the weight loss that brought about these benefits.
GLP-1s are recommended for weight loss, which can lower your risk of several cancers, including breast cancer. But the drugs aren't yet recommended specifically for the prevention of breast cancer, metastasis, or recurrence.
If you're in active cancer treatment, it's crucial to have a thorough conversation with your cancer care team about the risks and benefits of a GLP-1 drug before starting one.
GLP-1 and Breast Cancer FAQs
Do GLP-1s reduce breast cancer risk?
GLP-1 drugs have been linked to a lower risk of breast cancer, but it's not known whether it is the drugs themselves, or the weight loss induced by these drugs, that lowers cancer risk. Based on current evidence, experts say it's weight loss that lowers breast cancer risk.
Is Ozempic linked to a lower risk of cancer?
Ozempic is a GLP-1 drug, and these drugs have been linked to a lower risk of breast cancer, but they haven't been proven to directly cause the decrease in risk.
Should I take a GLP-1 if I'm worried about breast cancer risk?
If you are overweight and worried about breast cancer risk, experts recommend weight loss to lower your risk. GLP-1s help you lose weight, but weight loss through other methods can help lower breast cancer risk, too.
What did the 2026 ASCO study on GLP-1s and breast cancer show?
Two studies presented at the 2026 American Society of Clinical Oncology Annual Meeting showed a connection between GLP-1 use and breast cancer outcomes. One study showed that people taking GLP-1s were less likely to get breast cancer. Another study showed that people who started a GLP-1 while living with stage I, II, or III breast cancer were less likely to progress to stage IV.
Can GLP-1 medications prevent cancer?
Weight loss can lower your risk of certain cancers, and GLP-1s can help you lose weight. But it's not known whether GLP-1-induced weight loss lowers cancer risk more than weight loss by other means.
