Oral leukoplakia is a white lesion of the mouth that has the potential to develop into squamous cell carcinoma. The rate of malignant transformation is highly variable in different populations and ranges from less than 1% to approximately 20% in 1 to 30 years.230 A number of small uncontrolled trials have reported some degree of clinical improvement in 44 to 71% of those treated after supplementation with P-carotene (30 to 90mg/d)231232 or combinations of P-carotene and other antioxidants233 234 for 3 to 6 months. However, these trials may be too short to provide information about the actual benefit of P-carotene therapy, since less than half of all leukoplakias undergo malignant transformation within 2 years of diagnosis. In a longer trial, 50 men and women with oral leukoplakia were treated with 60mg/d of P-carotene for 6 months.235 In the 23 participants who consented to biopsies, 39% improved by at least one grade of dysplasia. After 6 months, those who were judged to have had a clinical response to the treatment (52%) were randomized to continued P-carotene treatment at 60mg/d or a placebo for an additional 12 months. The rate of relapse was similar between the groups treated with P-carotene (18%) and placebo (17%), suggesting that remissions induced by high-dose P-carotene supplementation are sustainable for at least one year in most oral leukoplakia patients. Two randomized controlled trials have examined the effect of P-carotene alone or in combination with other nutrients on oral leukoplakia in high-risk populations. In Uzbekistan, a combination of 100,000 IU/week of retinol, 40mg/d of P-carotene, and 80mg/week of vitamin E for 20 months significantly decreased the prevalence of oral leukoplakia by 35% in a study of 532 men with oral leukoplakia or chronic esophagitis.236a Supplementation of 131 Indian oral leukoplakia patients with 360mg/week of P-carotene significantly improved the regression rate to 33% compared with 10% for placebo.236b However, supplementation with 300 IU/week of retinol resulted in a regression rate of 52%. Smokers and tobacco chewers are at increased risk of oral leukoplakia. Given the potential for long-term oral P-carotene supplementation to increase lung cancer risk, its utility as a long-term treatment for oral leukoplakia must be questioned.
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