By now, you’ve heard plenty about GLP-1 drugs like Ozempic, Wegovy, Mounjaro, and Zepbound, which are now being regularly prescribed for weight loss and diabetes management. But the conversation around these medications has now expanded to other conditions, with researchers asking an intriguing question: Could GLP-1 drugs impact our risk of developing breast cancer, or even change the way cancer behaves?
The answer, according to newly released research, is a cautious maybe.
“The bottom line is that all the data we have so far is observational,” says Dr. Marisa Weiss, chief medical officer and founder of BreastCancer.org. “It's a signal, not proof. But all of these studies are all leaning in the same direction. So that's what's exciting from our point of view.”
GLP-1 medications mimic a hormone naturally produced in the body. They help regulate blood sugar, slow digestion, and increase feelings of fullness. That’s why they can be so effective for treating Type 2 diabetes and helping people lose weight. But weight and metabolism don't exist in isolation. Body fat, blood sugar, hormones, and inflammation are all connected — and researchers are increasingly interested in how those connections might influence cancer. Obesity, for example, is associated with a higher risk of developing breast cancer, as well as a greater risk of recurrence and death from breast cancer.
“Breast cancer is the most common cancer to affect women,” says Weiss, “and carrying extra weight does increase your risk for getting breast cancer, as well as having it recur and maybe even having it progress and becoming metastatic. So it's a significant public health issue, because obesity is rising. If there's a way to solve or reduce both public health crises, that's amazing.”
Here’s what we know so far.
GLP-1s may lower the risk of developing breast cancer
In a study of more than 110,000 women between 45 and 80 who had obesity, women taking a GLP-1 had about a 30 percent lower risk of developing breast cancer than women who weren't taking one. Another study, involving nearly 230,000 people, found that those taking GLP-1 medications for weight loss had a 41 percent lower risk of obesity-related cancers, including breast cancer, compared to people who were trying to lose weight through diet and exercise alone.
Weiss points to an important caveat here: These studies don't prove that GLP-1s prevent breast cancer.
"The studies are not what we call the randomized double-blind control trials, where, let's say, half the people get X and the other half gets Y, and they're supposed to be similar people in each group so that at the end of the study they can compare them and see what happened to each group,” Weiss explains. In other words, researchers don't yet know exactly why these associations between the medication and lower cancer risk exist, but the numbers are interesting enough that the field is paying close attention.
The drugs may help stop cancer from spreading
Obesity can involve chronic inflammation and changes in hormones and metabolism, which may influence the development and progression of cancer. Researchers are beginning to ask whether improving metabolic health itself might change the environment in which cancer develops and grows.
In one study of more than 10,000 people who had been diagnosed with cancer, those who started taking a GLP-1 after their diagnosis had a lower risk of the cancer metastasizing, or spreading to other parts of the body.
Why might that be? Weiss explains that “extra fat is very biologically metabolically active, so it's making all kinds of stuff — not just hormones, but inflammatory molecules that irritate cells and the barriers that contain these cells. We know that inflammation is associated with a higher risk of medical problems, including cancer, and that these inflammatory conditions seem to be reduced by these medicines and by losing weight.”
GLP-1s could potentially make cancer treatment easier
Breast cancer treatment can be grueling. Chemotherapy, hormonal therapy, and other treatments can bring fatigue, nausea, and a host of other side effects. Researchers have started looking at whether GLP-1 use might affect some of those complications.
In one study of more than 5,600 people with breast cancer who were receiving chemotherapy, those who were also taking GLP-1 medications were less likely to experience anemia, blood clots, low white blood cell counts, nausea, vomiting, fatigue, heart problems, and neuropathy (a nerve condition that causes pain or numbness).
Another study looked at lymphedema, the painful swelling that can develop after breast cancer treatment. Among nearly 62,000 people who had undergone a mastectomy, those taking a GLP-1 had a 63 percent lower risk of developing lymphedema.
Some research suggests better outcomes after a breast cancer diagnosis
Several studies have found that people with breast cancer who were taking GLP-1 medications had lower rates of death or recurrence than similar people who weren't taking them. One study, for example, found that women with breast cancer taking a GLP-1 were 60 percent less likely to die from breast cancer or any other cause over a 10-year period.
Another study of nearly 8,800 people with breast cancer and obesity who were receiving hormonal therapy found that those taking a GLP-1 had a 46 percent lower risk of death from any cause during about five-and-a-half years of follow-up.
“If you go through cancer treatment and they do a blood test and find pieces of cancer DNA floating around, that's not a good sign,” says Dr. Weiss. “It's a sign that there's some leftover cancer. And [researchers] found that the people who were on GLP-1s were less likely to have circulating tumor DNA after treatment.”
So, should you take a GLP-1 to prevent breast cancer? Not necessarily — but it may be a conversation worth having with your doctor. Researchers are only beginning to conduct studies specifically designed to answer these questions. But the findings are certainly encouraging.
“As a doctor in this space, an oncologist, and a survivor myself,” says Dr. Weiss, “we're always looking at how can we help the people that lean on us. That's why these studies are so important.”
