A new analysis of nearly 50 randomized trials suggests that GLP‑1 medications, popular for weight loss and diabetes control, probably do not alter the risk of developing any of 13 obesity‑related cancers.
Study Design and Findings
The research, published Monday in the Annals of Internal Medicine, was led by Dr. Cho‑Han Chiang, who was an internal medicine resident at Mount Auburn Hospital earlier this year and is now a medical oncology fellow at Northwell Health Cancer Institute. Chiang and his team examined 48 randomized controlled trials that included 94,245 patients with type 2 diabetes, overweight or obesity. More than 51,000 of those patients received a GLP‑1 medication while nearly 43,000 received a placebo, and the median follow‑up period was 70 weeks.
Chiang explained that the trials focused on 13 obesity‑related cancers identified by the International Agency for Research on Cancer Working Group. The study found, with moderate certainty, that GLP‑1 drugs had little or no effect on the risk of developing breast, kidney, thyroid and pancreatic cancers. For eight additional cancers—liver, gallbladder, colorectal, ovarian, endometrial, esophageal, meningioma and multiple myeloma—the effect was similar but with low certainty. The risk of gastric cancer was described as “very uncertain.”
Limitations of the Evidence
Chiang noted two major limitations. First, none of the nearly 50 trials he analyzed was designed to measure cancer outcomes. Second, the follow‑up period was relatively brief, lasting less than a year and a half. “Patients prescribed GLP‑1s should be monitored for far longer, particularly for slow‑growing diseases like breast and thyroid cancers,” said Dr. Kandace McGuire, chief of breast surgery at the Massey Comprehensive Cancer Center.
McGuire added that when researchers combine studies that were not looking at cancer risk, the results can sometimes contradict initial hypotheses. “Some of that may be just the makeup of the studies, rather than the actual data itself,” she said. “From a cancer prevention perspective, I think more data is needed.”
Expert Voices
Dr. Bassel El‑Rayes, deputy director of the O’Neal Comprehensive Cancer Center at the University of Alabama at Birmingham, praised the study’s reassurance. “This study gives us more reassurance about using these drugs in the treatment of things like obesity and type 2 diabetes,” he said. “There are questions left unanswered, like, could it be protective against cancer? Could there be a small increase of risk that we’re not recognizing yet?”
El‑Rayes also noted that the patients who are using the drugs at this moment are safer than what was previously thought. “The patients who are using the drugs at this moment are safer than what we thought before this paper came out,” he added.
Dr. Susan Wolver, who directs the Medical Weight Loss Program at VCU Health, said cancer is rarely a top concern when patients discuss GLP‑1 therapy. “Nobody comes to me and says, ‘I’d like to go on some medication to reduce my cancer risk,’” she said. “They’re going on these medications to lose weight, to improve their diabetes, their sleep apnea, their heart failure— all their obesity‑related conditions, but not cancer.”
Wolver praised the thoroughness of Chiang’s research and noted that GLP‑1 drugs are relatively young, with FDA approval for weight loss only in 2021 and 2023. “I am relieved with the findings of this study that there does not appear to be any increased cancer signals,” she said. “But I am also not dismayed that there was no reduction in the development of cancer or metastases, because I think we just didn’t have a long enough time.”
Clinical Take‑Away
The Food and Drug Administration warns people with a personal or family history of medullary thyroid carcinoma— a rare form of thyroid cancer— against certain GLP‑1 medications. This boxed warning stems from decade‑old rodent research. Chiang said that once an association is identified, it is difficult to dispel.
He also emphasized that the study does not prove that GLP‑1 drugs do not reduce cancer risk. “It’s not that GLP‑1 does not reduce the risk of cancer; I don’t think we can make that conclusion from our study,” Chiang said. “I would say GLP‑1 drugs probably do not increase the risk of cancer. It’s a little different.”
Key Takeaways
- GLP‑1 medications likely have little or no impact on the risk of 13 obesity‑related cancers.
- The evidence is limited by the lack of cancer‑specific endpoints and short follow‑up.
- Longer‑term studies are needed to confirm these findings and to explore potential protective effects.
The study provides reassurance for patients and clinicians using GLP‑1 drugs for weight loss and diabetes management, but it also highlights the need for extended monitoring and research to fully understand the long‑term cancer implications of these medications.
