According to a recent study published in JAMA Network Open, using one of the new GLP-1 drugs, such as Ozempic, in patients with type 2 diabetes is associated with a lower risk of developing 10 of 13 obesity-associated cancers compared to using insulin.
The study was retrospective, collecting data from more than 1.6 million patients with type 2 diabetes but no history of obesity-associated cancers prior to the study period. Using electronic health records, researchers had follow-up data for up to 15 years after the patients started taking a GLP-1 drug, insulin or metformin, between 2008 and 2015.
This type of study can't prove that the GLP-1 drugs caused the lower associated risks, but the results fit with previous findings. That includes results from a study that found a 32 percent lower overall risk of obesity-associated cancers after bariatric weight loss surgery.
In the new study, led by researchers at Case Western Reserve University School of Medicine, some of the GLP-1-associated risk reductions were quite substantial. Compared with patients taking insulin, patients taking a GLP-1 drug had a 65 percent lower associated risk of gallbladder cancer, a 63 percent lower associated risk of meningioma (a type of brain tumor), a 59 percent lower associated risk of pancreatic cancer and a 53 percent lower associated risk of hepatocellular carcinoma (liver cancer). The researchers also found lower associated risks for esophageal cancer, colorectal cancer, kidney cancer, ovarian cancer, uterine cancer and multiple myeloma.
Compared to insulin, the researchers did not see a reduced associated risk of thyroid and breast cancer. A lower risk of stomach cancer was calculated, but the finding was not statistically significant.
Gaps and goals
The GLP-1 drugs did not show such promising results compared to metformin in the study. Compared with patients taking metformin, patients on GLP-1 drugs saw lower associated risks of colorectal cancer, gallbladder cancer, and meningioma, but those calculations were not statistically significant. The results also unexpectedly showed a higher risk of kidney cancer for those taking GLP-1 drugs, but the cause of that potentially higher risk (which was not seen in the comparison with insulins) is unclear. The researchers called for more research to investigate that possible association.
Overall, the researchers call for many more studies to try to confirm a link between GLP-1 drugs and lower cancer risk, as well as studies to try to understand the mechanisms behind those potential risk reductions. It's unclear whether the lower risks are simply caused by weight loss, or whether insulin resistance, blood sugar levels or other mechanisms play a role.
The current study had several limitations given its retrospective, record-based design. Perhaps the most significant is that the data did not allow researchers to track individual patients’ weights over the study period. As such, researchers could not examine the associated reduction in cancer risk with actual weight loss. It is another aspect that warrants further investigation.
Still, the study yields another promising result for the blockbuster, albeit expensive, drug. The researchers propose expanding their work to assess whether GLP-1 drugs can be used to improve outcomes in patients with type 2 diabetes or obesity who have already been diagnosed with cancer, in addition to understanding whether the drugs can help prevent cancer.
