Chemoprevention of Oral Premalignant Lesions

Oral precancerous lesions have been relatively well studied in the chemoprevention research. Oral precancerous lesions are used as intermediate end point biological markers to help screen potential chemopreventive agents that might have utility in the prevention of oral and pharyngeal cancers. Chemoprevention of these lesions has direct clinical relevance and can also be used to screen agents that may have efficacy in the prevention of oral, pharyngeal, or other cancers. This chapter introduces various types of oral premalignant lesions, discusses design and interpretation issues of relevance to chemoprevention trials in this clinical setting, and reviews the results of chemoprevention trials of oral premalignancy. Several agents that have been evaluated for chemopreventive efficacy in oral precancerous lesions include various retinoids, β-carotene, the algae Spirulina fusiformis, vitamin E, selenium, tea, protease inhibitors, and bleomycin. Some of these agents have established efficacy in terms of regressing oral precancerous lesions, demonstrating proof of the principle behind chemoprevention of oral premalignancy. However, these same agents have limitations to their widespread use for this purpose. The chapter concludes with a discussion of the validity of oral precancerous lesions in predicting the efficacy of agents for oral-cancer prevention and discusses the challenges that lie ahead with regard to identifying suitable agents with clear evidence of efficacy but without significant toxicity.