GLP1 medications (used for weight management and diabetes, and other weight-related health issues) have many potential health benefits, and as for any medication, some potential risks. Where does colon cancer fall on this spectrum? If you search up GLP1 medications and colon cancer, the results you get will be conflicting and may seem downright confusing. Let’s dissect the existing data on this topic.
Some observational studies have raised a potential concern. An analysis of seven retrospective cohort studies suggested a 2.3 times higher risk of colon cancer in people receiving GLP1s, but no difference when compared with people using other drugs such as metformin or DPP4 inhibitors (both diabetes medications).
A meta analysis of 50 randomized controlled trials of at least 1 year in duration suggested a 27% increase in colon cancer which was significant only in shorter term trials. Authors hypothesized that this may be detection bias in the context of common side effects of GLP1s (example: a person develops diarrhea or constipation on GLP1, leading to a colonoscopy, and colon cancer is incidentally discovered).
Other studies have suggested no risk, or a protective effect in relation to colon cancer. For example, a recent meta analysis of randomized controlled trials found no effect on colon cancer risk. A database analysis suggested that 5-year mortality in people with colon cancer was 62% lower with GLP1 use in people with BMI over 35.
Individual randomized controlled clinical trials (the highest level of evidence) have not raised a signal for colon cancer. That being said, colon cancer typically take many years to develop, longer than the duration of most clinical trials.
What mechanisms could be at play? There are interesting considerations, some in favor of increased risk, and some in favor of protection. It has been questioned whether GLP1 medications may have proproliferative effects on the gastrointestinal lining that could stimulate cancers; whether the known anti-inflammatory and metabolic benefits may protect against cancers; or whether changes in gut bacteria may have an adverse effect on risk. Obesity is a risk factor for colon cancer; data from bariatric surgery studies suggest that weight loss can reduce colon cancer risk.
BOTTOM LINE: We don’t have a clear picture on if, or how, GLP1 medications may affect risk of colon cancer. Obesity is a risk factor for many types of cancer, including colon cancer. Dedicated long term studies are needed to explore the effect of GLP1 medications on cancer risk.
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