<qa>  What is the purpose of the trial of sulindac?The purpose of this protocol is to pilot a multi-center chemoprevention trial of sulindac, a pan-cyclooxygenase COX inhibitor, for oral leukoplakia through an international collaboration between Memorial Sloan-Kettering Cancer Center MSKCC, New York, Regional Cancer Centre RCC in Trivandrum, India and the Amrita Institute of Medical Sciences AIMS, Kerala, India. Specifically, we will conduct a 66 subject, 2-arm, double-blind, placebo-controlled randomized study of sulindac 150 mg bid to test the clinical efficacy, safety and molecular effects of sulindac against OPL and OPL tissue. Oral leukoplakia subjects will be enrolled from both RCC, AIMS and MSKCC, however, we expect that most subjects will be recruited from AIMS due to the substantially higher prevalence of this condition among the Indian compared to the US population. 