Metformin for the Prevention of Oral Cancer in Patients With Oral Premalignant Lesions

PRIMARY OBJECTIVE: I. To evaluate the transformation-free-survival in lesion types erythroplakia (EP) and verrucous hyperplasia (VH). 'Transformation' is defined as the development of invasive cancer. SECONDARY OBJECTIVE: I. To evaluate the current spontaneous regression rates, i.e., percentages of patients having lesion disappear within 1-year post treatment, in all four lesion types and compare them with historical documented regression rate in literature. EXPLORATORY OBJECTIVE: I. To evaluate the transformation-free-survival in lesion types homogenous leukoplakia (HL) and non-homogenous leukoplakia (NHL). OUTLINE: Patients receive metformin orally (PO) once daily (QD) on days 1-3 and then PO twice daily (BID) for up to 12 months in the absence of unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 24 months.