Women taking popular GLP-1 weight loss drugs like Ozempic and Wegovy had a 30 percent reduced risk of developing breast cancer than people not on the drugs, according to a new study from the University of Pennsylvania Perelman School of Medicine.
The findings build on years of previous studies that tie GLP-1 use to improved outcomes for multiple types of the life-threatening cancer — although past research has also found the drugs have little effect on reducing the risk of obesity-related cancers like breast cancer.
Still, the school’s observations could help fight one of the most common cancers among women in the U.S. Breast cancer accounts for nearly a third of all cases and the American Cancer Society says about 42,140 women are expected to die from breast cancer this year.
And, the researchers say their study supports examining the medications’ abilities to improve overall cancer prevention.
“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,” Dr. Elizabeth McDonald, a radiologist and professor at the school, explained in a statement.
“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, so we’re eager to study them in this context,” she added.
The study examined the health of more than 110,000 overweight American women between the ages of 45 and 80 over the course of three years from 2022-2025, 15,264 of whom were on the drugs initially.
It did not take into account what kinds of GLP-1 drugs the patients used during that time, as well as a patient’s genetic history or cancer stage when they were diagnosed.
Future research will address some of these factors, the school said, and McDonald and team are working to set up a clinical trial to assess whether the drugs can lower rates of breast cancer in women who are at higher risk and those with a history of breast cancer.
So, what do the researchers think may be behind these conclusions?
Well, the weight loss is a big part of it.
GLP-1 drugs work by mimicking a hormone the body produces to regulate blood sugar and appetite called glucagon‑like peptide‑1, or GLP-1. It controls cravings, helping users to shed dozens of pounds in just months.
The drugs were initially targeted specifically for diabetes patients, but millions now take them to help lose weight.
Obesity has been pervasive in the U.S. thanks to an inactive lifestyle, ultraprocessed diet and other factors, with rates projected to dramatically rise by 2050. More than 100 million Americans live with obesity now, federal data shows, and women are disproportionately affected.
The chronic condition, characterized by excessive body fat, is a known risk factor for breast and other types of cancer.
Notably, obesity triggers harmful inflammation in the body: something researchers have long suspected plays a role in affecting cancer tumor growth.
GLP-1 drugs help to tackle both of those problems, although it remains unclear whether those effects are directly responsible for the new study’s results.
Whatever is the case, the doctors say using the drugs could be beneficial for women to avoid some of the more invasive methods of treatment for breast cancer.
Mastectomies are surgeries that remove the whole breast, for example.
“Ultimately, we want to find better options to prevent breast cancer,” McDonald said. “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.”
