GLP-1 Medications and Breast Cancer Research

Originally, scientists developed GLP-1 drugs to control blood sugar in people with Type 2 diabetes. Today, doctors also use these medications to manage obesity, heart disease, and some drug use disorders.

New research suggests that GLP-1 drugs may lower breast cancer risk. They may also improve outcomes for people who already have a breast cancer diagnosis. However, researchers say we need more evidence before drawing firm conclusions. Most studies so far show encouraging results, but scientists need to examine these effects in more diverse groups.

Researchers especially want to study people who do not have diabetes or obesity. These groups remain less represented in current research. For now, the findings offer promising insights into the potential role of GLP-1 drugs in breast cancer prevention and care. Scientists will need larger and longer-term studies to understand their benefits and limitations.

GLP-1 is a natural hormone that helps control blood sugar and appetite. It boosts insulin release, lowers blood sugar hormones, and slows digestion to keep you full longer. Ozempic, Wegovy, Mounjaro, and Zepbound are brand-name medications that mimic GLP-1. They can help manage blood sugar and support weight loss when prescribed by a healthcare professional.

1. GLP-1 drug users may have a lower risk of breast cancer. One study followed nearly 110,000 women with obesity. It found about a 30% lower breast cancer risk among GLP-1 users than non-users. Another study examined about 230,000 people. GLP-1 users had a 41% lower risk of obesity-related cancers, including breast cancer. Tirzepatide showed a greater risk reduction than semaglutide in this analysis. However, researchers need more evidence to explain this difference.

A third study included about 148,700 women without diabetes. GLP-1 use linked to a small reduction in hormone receptor-positive, HER2-negative breast cancer. These findings look promising. However, they do not prove that GLP-1 drugs prevent breast cancer. More research is needed to understand whether the benefits come from the drugs themselves, weight loss, or other health changes.

2. Obesity can increase inflammation and hormonal changes that may help cancer spread. Researchers are now exploring whether GLP-1 drugs could reduce this risk. One study followed more than 10,200 people with early-stage lung, breast, colorectal, or liver cancer. Patients who started a GLP-1 drug after their diagnosis showed a lower risk of cancer spreading than those who did not take these medications.

These findings suggest that GLP-1 drugs may offer benefits beyond weight management. However, researchers need more studies to determine whether GLP-1 medications directly reduce metastasis risk.

3. Less adverse effects from treatment. Although the difference was minimal, GLP-1 users had somewhat less and later-onset side effects when using CDK4/6 inhibitors for hormone receptor-positive breast cancer. GLP-1 users experienced reduced incidences of anemia, blood clots, low white blood cell counts, sepsis, nausea, vomiting, exhaustion, heart issues, and neuropathy among over 5,600 chemotherapy patients. Additionally, GLP-1 users had a 63% decreased risk of lymphedema among approximately 62,000 mastectomy patients.

4. Improved results for breast cancer that has spread. GLP-1 users had a 60% lower risk of dying from any cause during a ten-year period, according to a study that compared 1,600 GLP-1 users with 1,600 non-users. GLP-1 users had approximately a 90% lower death risk and fewer recurrences among patients with both diabetes and breast cancer compared to those on metformin or insulin; however, experts pointed out that the study lacked information on hormone-receptor status and complete treatment histories, casting doubt on its validity. Additionally, adding a GLP-1 was associated with a 46% decreased risk of death over approximately 5.5 years in roughly 8,800 patients with obesity and breast cancer receiving hormonal therapy.

And among people with diabetes and breast cancer that had spread to the brain, GLP-1 users had a 32% lower three-year death risk though this benefit applied to semaglutide, dulaglutide, and tirzepatide, not liraglutide.

GLP-1 use was associated with better outcomes in people with hormone receptor-positive ductal carcinoma in situ (DCIS), a non-invasive form of breast cancer. In a real-world study of more than 6,000 patients receiving hormonal therapy, those taking GLP-1 drugs had a 93.5% five-year survival rate, compared with 85.7% among non-users.

5. The GLP-1 group also had a 74% lower risk of invasive or metastatic breast cancer. However, the researchers noted that the overall rate of progression was unusually high for DCIS, raising questions about whether some cases may have been misclassified.

Because this was a retrospective observational study, the findings do not prove that GLP-1 drugs prevent cancer progression or improve survival. Researchers say prospective studies are needed to confirm the results and understand whether GLP-1 therapy directly contributes to better DCIS outcomes.

The benefits may not apply to people without diabetes or obesity. So far, studies have only included people using GLP-1 drugs for these conditions. Researchers have also relied on retrospective studies. They reviewed existing medical records instead of tracking outcomes in real time.

Still, the findings support a broader cancer theory. Metabolism, inflammation, and body composition may affect how cancer develops and spreads. Treatments that target these factors could eventually become part of cancer care.