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GLP-1 receptor agonists were not linked to an increased risk of breast cancer, new research showed.

In a systematic review and meta-analysis of 52 randomized, controlled studies, the breast cancer rates in adults with obesity or diabetes who were treated with such drugs were almost identical in comparison to other drug classes (relative risk 0.98, 95% CI 0.76- 1.26) Dr. med. Giovana Fagundes Piccoli from the Hospital de Clínicas de Porto Alegre in Brazil.

Across the cohort, there were 130 cases of breast cancer in 48,267 patients treated with a GLP-1 receptor agonist, versus 107 cases in 40,755 controls, Piccoli explained at the Endocrine Society’s virtual ENDO 2021 meeting.

Control subjects included patients who received either placebo or active treatment with a non-GLP-1 receptor agonist.

There was also no difference in the risk of benign breast neoplasms in patients with GLP-1 receptor agonists compared to other drug types (RR 0.99, 95% CI 0.48 to 2.01).

And there was no difference between individual GLP-1 receptor agonists. To assess this, the researchers compared each of the four main drugs in the class – liraglutide (Saxenda, Victoza), dulaglutide (Trulicity), semaglutide (Ozempic, Rybelsus), and albiglutide (Tanzeum) – to exendin-4 mimetics including exenatide (Byetta, Bydureon) and lixisenatide (adlyxin).

Comparing studies with an open design with double-blind studies showed no difference in breast cancer risk.

Piccoli said her group wanted to dig deeper into this topic after the 2015 SCALE study of obesity and prediabetes, which found more breast neoplasms in patients who received liraglutide than placebo (4.36 vs. 1.80 per 1,000 person-years). Most of the neoplasms in this study developed within the first year of treatment with GLP-1 receptor agonists and were more common in participants who had lost more weight on the drug.

“I think the results of our meta-analysis will provide more safety information about this treatment,” Piccoli said during a press conference. “Patients, physicians, and other health professionals can more safely ensure the safety of these drugs.”

For this analysis, her group searched the MEDLINE, Embase, Web of Science, and CENTRAL databases to include randomized trials evaluating GLP-1 receptor agonists in adults with overweight, obesity, prediabetes, or type 2 diabetes who also had breast cancer or benign breast neoplasm reported incident.

In the meta-analysis, the age of the participants was between 45 and 70 years and the follow-up period was between 24 weeks and 7.5 years.

Piccoli emphasized that these results are only relevant for patients treated with a GLP-1 receptor agonist for diabetes control or weight loss without pre-existing breast cancer. She added that patients with a history of breast cancer – or any cancer – were typically excluded from the studies included in this meta-analysis.

“In a general population with type 2 diabetes and obesity, we can say [GLP-1 receptor agonists] are safe, “Piccoli said. But the safety of the class in patients with a history of breast cancer is less certain, she added.

  • Kristen Monaco is a contributor focused on endocrinology, psychiatry, and dermatology news. She is based in New York City and has been with the company for nearly five years.


Piccoli reported on the support of the Research Incentive Fund of the Hospital of Clínicas de Porto Alegre. Other study authors reported disclosures.