Glucagon-like peptide 1 receptor agonists (GLP-1 RAs) are associated with a reduced risk for colorectal cancer (CRC) in patients with type 2 diabetes, with and without overweight or obesity, according to a new analysis.
In particular, GLP-1 RAs were associated with decreased risk compared with other antidiabetic treatments, including insulin, metformin, sodium-glucose cotransporter 2 (SGLT2) inhibitors, sulfonylureas, and thiazolidinediones.
More profound effects were seen in patients with overweight or obesity, "suggesting a potential protective effect against CRC partially mediated by weight loss and other mechanisms related to weight loss," Lindsey Wang, an undergraduate student at Case Western Reserve University, Cleveland, Ohio, and colleagues wrote.
Testing Treatments
GLP-1 RAs, usually given by injection, are approved by the US Food and Drug Administration to treat type 2 diabetes. They can lower blood sugar levels, improve insulin sensitivity, and help patients manage their weight.
Diabetes, overweight, and obesity are known risk factors for CRC and make prognosis worse. Wang and colleagues hypothesized that GLP-1 RAs might reduce CRC risk compared with other antidiabetics, including metformin and insulin, which have also been shown to reduce CRC risk.
Using a national database of more than 101 million electronic health records, Wang and colleagues conducted a population-based study of more than 1.2 million patients who had medical encounters for type 2 diabetes and were subsequently prescribed antidiabetic medications between 2005 and 2019. The patients had no prior antidiabetic medication use nor CRC diagnosis.
The researchers analyzed the effects of GLP-1 RAs on CRC incidence compared with the other prescribed antidiabetic drugs, matching for demographics, adverse socioeconomic determinants of health, pre-existing medical conditions, family and personal history of cancers and colonic polyps, lifestyle factors, and procedures such as colonoscopy.
During a 15-year follow-up, GLP-1 RAs were associated with decreased risk for CRC compared with insulin (hazard ratio [HR], 0.56), metformin (HR, 0.75), SGLT2 inhibitors (HR, 0.77), sulfonylureas (HR, 0.82), and thiazolidinediones (HR, 0.82) in the overall study population.
For instance, among 22,572 patients who took insulin, 167 cases of CRC occurred, compared with 94 cases among the matched GLP-1 RA cohort. Among 18,518 patients who took metformin, 153 cases of CRC occurred compared with 96 cases among the matched GLP-1 RA cohort.
GLP-1 RAs also were associated with lower but not statistically significant risk than alpha-glucosidase inhibitors (HR, 0.59) and dipeptidyl-peptidase-4 (DPP-4) inhibitors (HR, 0.93).
In patients with overweight or obesity, GLP-1 RAs were associated with a lower risk for CRC than most of the other antidiabetics, including insulin (HR, 0.5), metformin (HR, 0.58), SGLT2 inhibitors (HR, 0.68), sulfonylureas (HR, 0.63), thiazolidinediones (HR, 0.73), and DPP-4 inhibitors (HR, 0.77).
Consistent findings were observed in women and men.
"Our results clearly demonstrate that GLP-1 RAs are significantly more effective than popular antidiabetic drugs, such as metformin or insulin, at preventing the development of CRC," said Nathan Berger, MD, co-lead researcher, professor of experimental medicine, and member of the Case Comprehensive Cancer Center.
Targets for Future Research
Study limitations include potential unmeasured or uncontrolled confounders, self-selection, reverse causality, and other biases involved in observational studies, the research team noted.
Further research is warranted to investigate the effects in patients with prior antidiabetic treatments, underlying mechanisms, potential variation in effects among different GLP-1 RAs, and the potential of GLP-1 RAs to reduce the risks for other obesity-associated cancers, the researchers wrote.
"To our knowledge, this is the first indication this popular weight loss and antidiabetic class of drugs reduces incidence of CRC, relative to other antidiabetic agents," said Rong Xu, PhD, co-lead researcher, professor of medicine, and member of the Case Comprehensive Cancer Center.
The study was supported by the National Cancer Institute Case Comprehensive Cancer Center, American Cancer Society, Landon Foundation-American Association for Cancer Research, National Institutes of Health Director's New Innovator Award Program, National Institute on Aging, and National Institute on Alcohol Abuse and Alcoholism. Several authors reported grants from the National Institutes of Health during the conduct of the study.
The study was published online on December 7, 2023, in JAMA Oncology.
Carolyn Crist is a health and medical journalist who reports on the latest studies for Medscape, MDedge, and WebMD.
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