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.
This phase I trial tests whether metformin works in reducing the annual transformation (development of invasive cancer) of oral precancerous lesions into cancerous lesions. Metformin is a drug approved for the treatment of diabetes, but studies have shown that it may have some anticancer properties. Giving metformin may help prevent or slow the development of oral cancer from precancerous lesions.