Bodmer and colleagues carried out a case-control study using the UK General Practice Research Database to explore the association between the use of metformin and other anti-diabetes drugs and the risk of pancreatic cancer. They found that the use of metformin was associated with a decreased risk of pancreatic cancer in women only (adjusted odds ratio [OR] 0.43, 95% confidence interval [CI] 0.23–0.80). Use of sulphonylureas (≥30 prescriptions, adjusted OR 1.90, 95% CI 1.32–2.74) and of insulin (≥40 prescriptions, adjusted OR 2.29, 95% CI 1.34–3.92) were associated with an increased risk of pancreatic cancer.
A retrospective cohort study in over 3500 people with type 2 diabetes by Bo et al explored the association between the type and duration of anti-diabetes therapies and cancer and other-than-cancer mortality. The study found that cancer-related death occurred in 1.6% of metformin users compared with 3% of sulphonylurea users, 4.8% of insulin users and 4.2% of those on diet alone. All-cause mortality was also lower in those people taking metformin (9.2% compared with 13.1% on sulphonylureas, 26.8% on insulin and 11% on diet alone). The authors concluded that the lower risk of cancer-related mortality in metformin users compared with non-metformin users or those on diet only may represent another reason to choose metformin as a first-line therapy in type 2 diabetes.
Currie and colleagues used data from over 350 primary care practices in the UK to investigate whether survival after a diagnosis of a solid-tumour cancer is reduced in people with diabetes compared with those without diabetes, and the influence of metformin treatment on survival after cancer diagnosis. 112 408 individuals were identified, and 7.5% of these had type 2 diabetes. Cancer mortality was increased in those with diabetes compared with those without (OR 1.09, 95% CI 1.06–1.13). Mortality was increased in those with breast (OR 1.32, 95% CI 1.17–1.49) and prostate cancer (OR 1.09, 95% CI 1.08–1.31), and decreased in those with lung cancer (OR 0.84, 95% CI 0.77–0.92). Mortality was increased in those people with diabetes treated with sulphonylureas (OR 1.13, 95% CI 1.05–1.21) or insulin (OR 1.13, 95% CI 1.01–1.27), and decreased in those on metformin monotherapy (OR 0.85, 95% CI 0.78–0.93). The authors commented that the observations with metformin raise the possibility that this drug may come to play a wider role in cancer prevention and therapy in the future.
References
Bodmer M et al (2012) Use of antidiabetic agents and the risk of pancreatic cancer: A case–control analysis. Am J Gastroenterology doi:10.1038/ajg.2011.483
Bo S et al (2012) Cancer mortality reduction and metformin: a retrospective cohort study in type 2 diabetic patients. Diabetes Obes Metab 14: 23–29
Currie CJ et al (2012) Mortality after incident cancer in people with and without type 2 diabetes: Impact of metformin on survival Diabetes Care 35: 299–304
