A few reports have suggested that people who take metformin, one of the most widely prescribed drugs for Type 2 diabetes, have a lower risk of getting colorectal cancer. Later reviewers of these studies, however, concluded that they were possibly flawed, which left the question open.
To address that concern, researchers recently conducted a study, published in the journal Cancer Epidemiology, Biomarkers & Prevention, of the relationship between metformin use and colorectal cancer, and they came away with some good news: Long-term use of metformin is associated with a decreased risk for colorectal cancer in men with diabetes. As one of the authors put it, “If our findings are confirmed, metformin may have a role in the chemoprevention of colorectal cancer.”
The study involved people who participated in the Kaiser Permanente Northern California Diabetes Registry. The subjects were at least 40 years old, had been diagnosed with diabetes, and were taking at least one diabetes-related medication. Nearly 48,000 patients were included, and almost half of them received metformin.
The “fully adjusted model,” as the researchers expressed it, showed “no association between ever metformin use and risk for colorectal cancer.” In addition, the researchers reported that long-term users of metformin and those who took higher doses showed a lower risk. These findings about duration of use, however, applied only to men, not to women.
The researchers advised that their findings need to be confirmed in larger studies. But because earlier studies have indicated that people with Type 2 diabetes have an increased risk of certain types of cancer, this latest research suggests that there is much fascinating research to be done on the as-yet unexplained association between metformin and decreased colorectal cancer risk.