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No Increased Breast Cancer Risk Found With GLP-1 Agonists

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No Increased Breast Cancer Risk Found With GLP-1 Agonists

Researchers in Brazil have found no link between a widely used type of diabetes medication and breast cancer, a new study reports. Their findings were reported at the 2021 virtual meeting of the Endocrine Society.

The medications they studied are what are known as GLP-1 receptor agonists. These drugs are also called incretin mimetics, because how they function is based on the action of incretins, which are hormones that help control the working of the pancreas. GLP-1 is an incretin that stimulates the pancreas to make more insulin after meals, which helps control blood sugar levels.

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GLP-1 receptor agonists mimic the action of the natural GLP-1 manufactured in the pancreas, but while the effects of pancreatic GLP-1 are brief, the effects of GLP-1 receptor agonists can last for days. Some of the better known GLP-1 receptor agonists are exenatide (brand names Byetta, Bydureon), semaglutide (Ozempic), liraglutide (Victoza, Saxenda), albiglutide (Tanzeum), dulaglutide (Trulicity), and lixisenatide (Lyxumia). They are liquid medications that are self-administered through an injection under the skin, although in 2019 the U.S. Food and Drug Administration (FDA) approved the first oral GLP-1 receptor agonist — semaglutide, which is marketed as Rybelsus. Although GLP-1 agonists were developed for treating type 2 diabetes, they have recently been shown to be effective for weight loss in obese people without diabetes when administered along with diet control and exercise.

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The authors of the new study, which was led by Giovana Fagundes Piccoli, MD, of the Hospital de Clinicas de Porto Alegre in Porto Alegre, Brazil, set out to investigate earlier reports that had suggested a link between the use of GLP-1 receptor agonists and breast cancer. As they explained, “Risk of cancer is a major concern in the development of drugs for the treatment of obesity and diabetes. In randomized controlled trials (RCTs) of the Liraglutide Clinical Development Program, subjects treated with a glucagon-like peptide-1 receptor agonist (GLP-1RA) had a higher absolute number of breast cancer events.” This earlier report, they said, found more breast neoplasms (which include not only cancer but also high-risk lesions as well as benign growths) in patients using liraglutide than in patients using a placebo (an inactive substance). Most of these neoplasms occurred in the first year of use of the GLP-1 receptor agonist. The researchers decided to investigate further and to assess whether patients treated with GLP-1 receptor agonists did, in fact, have a higher risk of breast neoplasms.

By searching such databases as MEDLINE, Embase, and Web of Science, they did a review and meta-analysis  (analysis of data from several clinical trials) of 52 randomized controlled trials. Of these, the researchers said, 50 reported breast cancer events and 11 reported benign breast neoplasms. The patients ranged in age from 45 to 70 and the follow-up periods ranged from 24 weeks to 7 1/2 years. The researchers identified 48,267 patients who had been treated with GLP-1 receptor agonists. The researchers concentrated on patients who were being treated with a GLP-1 receptor agonist for diabetes or obesity and did not have preexisting breast cancer; they excluded subjects who had a history of breast cancer.

Among all the patients, there were 130 incidents of breast cancer. In a control group of 40,755 subjects who did not receive GLP-1 receptor agonists, 107 were diagnosed with breast cancer. Taken as a percentage, the breast cancer rates were virtually the same in both groups. The researchers also compared the effects of the four major GLP-1 receptor agonists — liraglutide, dulaglutide, semaglutide, and albiglutide — and determined there was no difference among them.

The researchers’ conclusion was succinct: “Treatment with GLP-1RAs for obesity and diabetes does not increase the risk of breast neoplasms.” And in a press conference, Dr. Piccoli added, “I think that the results of our meta-analysis adds more security and safety information about this treatment. Patients, doctors, and other health professionals can be more secure of the safety of these drugs.”

Want to learn more about GLP-1 agonists? Read “Non-insulin Injectable Diabetes Medications.”

Living with type 2 diabetes? Check out our free type 2 e-course!

Joseph Gustaitis

Joseph Gustaitis

Joseph Gustaitis on social media

A freelance writer and editor based in the Chicago area, Gustaitis has a degree in journalism from Columbia University. He has decades of experience writing about diabetes and related health conditions and interviewing healthcare experts.

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