Meta-analyses have suggested that type 2 diabetes is associated with an increased risk of cancer, but that antidiabetes medications may reduce this risk. Several observational studies have found that metformin reduced the risk of cancer by approximately one-third, but this research may be prone to bias and randomized controlled trials (RCTs) have not been able to confirm these results. Published in Diabetes Care, a new study reviewed longitudinal data from the German Disease Analyzer database of 22,556 patients who received a diagnosis of type 2 diabetes from January 2000 to December 2012 and who used any diabetes drug after diagnosis of diabetes. Metformin was the most commonly used medication; among those who ever used metformin, 83.7% used it as their only first diabetes medication.
Approximately 6% of patients developed cancer after their diabetes diagnosis, with mean follow-up after first diagnosis of diabetes until incidence of cancer or end of observation of 4.8 years. No increased risk of cancer of all sites was seen in patients taking other first diabetes medication (sulfonylurea, insulin, or other medication but metformin) compared to patients taking metformin as first diabetes medication. While this study attempted to avoid immortal time bias and bias from time lag and latency, future studies should avoid time-related biases to further assess associations between diabetes medication and site-specific cancer, especially colorectal, breast, pancreatic, liver, and hepatocellular cancer.
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