Weight-loss medications have become some of the most widely used and closely watched drugs in recent years. Semaglutide (sold under brand names such as Ozempic® and Wegovy®) and tirzepatide (sold as Zepbound® and Mounjaro®) have seen especially rapid growth in use.
As more people take these medications, questions about their long-term safety have escalated, including whether they may affect cancer risk. Research so far has produced mixed findings: Some studies have raised questions about possible links to certain cancers, while other large studies and reviews have found no increased overall cancer risk.
Read on to learn more about the following topics:
- What are GLP-1 drugs and how do they work?
- Do GLP-1 medications cause cancer?
- Do weight-loss drugs reduce cancer risk?
- Weighing the risks and benefits of GLP-1 drugs
If you or a loved one is concerned about possible signs or symptoms of cancer and would like an initial consultation or a second opinion, call us 24/7 at (877) 460-4673.
What Are GLP-1 Drugs and How Do They Work?
Many newer diabetes and weight-loss medications belong to a group called glucagon-like peptide-1 (GLP-1) receptor agonists, or GLP-1 drugs. The U.S. Food and Drug Administration (FDA) has approved several of these medications to help people with type 2 diabetes manage their blood sugar. Some are also FDA-approved to help people who are obese or overweight shed pounds and maintain weight loss.
GLP-1 drugs work in several ways. They mimic the effects of a hormone naturally made in the body called GLP-1. In people with diabetes, these medications help the pancreas release more insulin when blood sugar is elevated, which helps lower blood sugar. They may also slow digestion and reduce appetite, which may help with weight loss.
Tirzepatide, while often discussed alongside GLP-1 medications, works somewhat differently. It activates both GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptors and is approved under the brand name Mounjaro® for type 2 diabetes and Zepbound® for chronic weight management.
Some of the most commonly recognized medications in this group include:
- Semaglutide (Ozempic®, Wegovy®, Rybelsus®)
- Tirzepatide (Mounjaro®, Zepbound®)
- Dulaglutide (Trulicity®)
- Exenatide (Byetta®, Bydureon®)
- Liraglutide (Victoza®, Saxenda®)
Most of these medications are given as an injection under the skin. Rybelsus® (semaglutide) is taken by mouth as a tablet. The specific brand, dose and form depend on the medication and the condition being treated.
It’s also important to know that not every brand in this list has the same FDA-approved uses. For example, Ozempic® is approved for type 2 diabetes, while Wegovy® is approved for chronic weight management. Doctors may sometimes prescribe medications for uses other than their FDA-approved indications, known as off-label use.
Do GLP-1 Medications Cause Cancer?
Because GLP-1 medications are relatively new and now widely used, researchers continue to study their long-term safety, including whether they affect cancer risk. So far, research has produced mixed findings, but there’s no clear evidence that these medications cause cancer in people.
Some studies have raised concerns about a possible connection between GLP-1 medications and thyroid cancer. One large study found that people with type 2 diabetes who took GLP-1 receptor agonists for one to three years had a higher risk for developing thyroid cancer, mainly a rare type called medullary thyroid cancer. However, the type of study conducted may show an association but cannot prove that the medication caused the cancer.
Researchers have also investigated a possible link to pancreatic cancer, but findings have been inconsistent. A review of tirzepatide found limited evidence that it increases pancreatic or thyroid cancer risk and noted that more research is needed.
More recent evidence is reassuring. A systematic review and meta-analysis found that semaglutide wasn’t associated with an increased risk for developing cancer overall, including thyroid or pancreatic cancer. The researchers said this conclusion was supported by a high level of evidence.
There’s also an important distinction between a potential risk and a proven risk. Animal studies have found thyroid C cell tumors with some GLP-1 medications, but it isn’t known whether these findings apply to people. As a precaution, the FDA warns against using these medications in people with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2 (MEN 2).
Sasan Fazeli, M.D., an oncologic endocrinologist and clinical director of the Thyroid and Endocrine Cancer Clinic at City of Hope® Cancer Center Duarte, says the bottom line is that current research doesn’t show that GLP-1 medications generally cause cancer.
“While some studies have raised questions about specific cancers, particularly thyroid cancer, other high-quality research hasn’t found an increased cancer risk,” Dr. Fazeli explains.
“Correlations are not causation. That’s why researchers continue to study these medications as more people use them over longer periods,” he adds. “Furthermore, we don’t yet have evidence of an association between GLP-1 drugs and the most common thyroid cancers, which are derived from follicular cells, including papillary, follicular and oncocytic thyroid cancers.”
Do Weight-Loss Drugs Reduce Cancer Risk?
There’s another side to the research on GLP-1 drugs and cancer: These medications may reduce the risk for developing some cancers associated with obesity. Overweight and obesity are linked to an increased risk for at least 13 types of cancer, including colorectal, endometrial, liver, kidney, pancreatic and postmenopausal breast cancers.
Researchers at Case Western Reserve University School of Medicine studied more than 1.6 million people with type 2 diabetes and found that those taking GLP-1 drugs had a significantly lower risk for developing 10 obesity-associated cancers compared with people taking insulin. These included:
- Colorectal cancer
- Endometrial cancer
- Esophageal cancer
- Gallbladder cancer
- Kidney cancer
- Liver cancer
- Meningioma
- Multiple myeloma
- Ovarian cancer
- Pancreatic cancer
The findings suggest that GLP-1 medications may help reduce some obesity-associated cancer risk, but they don’t prove that the drugs prevent cancer. The study found no significant reduction in postmenopausal breast or thyroid cancer, and the lower cancer rates weren’t seen when GLP-1 drugs were compared with metformin.
Early laboratory research also suggests a possible connection between weight loss and cancer risk. In a study of obese mice with breast tumors, tirzepatide boosted weight loss and slowed tumor growth, possibly by reducing some of the biological effects of obesity. However, because this was an animal study, it isn’t known whether the same effects occur in people.
Key takeaway: Losing excess weight may help decrease the risk for developing several obesity-associated cancers, and GLP-1 medications may contribute to that benefit. More research is needed to establish whether the medications directly prevent cancer or whether the benefit comes mainly from weight loss and improved metabolic health.
Weighing the Risks and Benefits of GLP-1 Drugs
For anyone considering a GLP-1 medication for weight loss, it’s important to understand both the potential benefits and possible risks. These medications may be helpful for weight management and overall health, but they may not be appropriate for everyone.
“It’s essential to talk with your doctor before starting a GLP-1 medication,” says Dr. Fazeli. “Depending on your medical history, that may include a thyroid specialist, endocrinologist or your cancer care team. They can help you understand the potential benefits and risks and determine whether the medication is right for you.”
A patient’s healthcare team may also explain how a GLP-1 medication may fit with a person’s cancer history, other medications and overall treatment plan.
If you or a loved one is concerned about possible signs or symptoms of cancer and would like an initial consultation or a second opinion, call us 24/7 at (877) 460-4673.