Metformin Reduces The Increased Risk Of Oral Squamous Cell Carcinoma Recurrence In Patients With Type 2 Diabetes Mellitus: A Cohort Study With Propensity Score Analyses

Background: To investigate the impact of type 2 diabetes mellitus (T2DM) and metformin treatment on the prognosis of oral squamous cell carcinoma (OSCC) patients received radical surgical treatment.Methods: Eight hundred and fifty-two patients with OSCC between January 2011 and January 2015 were included in the cohort study. Propensity score analysis was used to balance the characteristics of patients with or without T2DM and those of patients with T2DM treated with or without metformin. Five-year OSCC-free survival (OFS) was used to evaluate the prognosis of OSCC patients.Results: Two hundred and sixty-nine patients without T2DM and 138 patients with T2DM were selected after the propensity score matching. The 5-year OFS of patients with T2DM was significantly lower than that of those without T2DM, both before (P = 0.019) and after (P = 0.014) the propensity score matching. Forty-four metformin users of OSCC patients with T2DM and 44 patients never users were further compared after the propensity score matching. The 5-year OFS of metformin users was significantly higher than that of metformin never users both before (P = 0.005) and after (P = 0.002) the propensity score matching.Conclusions: T2DM is associated with a higher risk of OSCC recurrence that can be reduced by metformin treatment.