Effect of metformin on the incidence of head and neck cancer in diabetics

BACKGROUND: The purpose of this study was to examine the effect of metformin on head and neck cancer in patients with diabetes. METHODS: We compared 66,600 patients, all with diabetes and all newly diagnosed with head and neck cancer in 2002. Half were being treated with metformin for diabetes (Met(+) ) and half were not (Met(-) : controls). All were matched for comorbidities (obesity, coronary artery disease, hyperlipidemia, and hypertension), sex, and age. The risk of head and neck cancer at the end of 2011 was determined. RESULTS: The incidence of head and neck cancer was 34% lower in the Met(+) cohort than in the Met(-) cohort (adjusted hazard ratio [HR] = 0.66; 95% confidence interval [CI] = 0.55-0.79). The risks for oropharyngeal cancer (adjusted HR = 0.66; 95% CI = 0.17-0.74) and nasopharyngeal carcinoma (NPC; adjusted HR = 0.50; 95% CI = 0.31-0.80) were significantly lower in the Met(+) cohort than in the Met(-) cohort. CONCLUSION: Metformin is associated with a lower risk of developing head and neck cancer in patients with diabetes.