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.