Risk factors for leukoplakia and malignant transformation to oral carcinoma: a leukoplakia cohort in Taiwan

The effects of betel nut chewing, smoking and alcohol on the occurrence of leukoplakia and its malignant transformation to oral carcinoma were quantif ied in a leukoplakia cohort (n = 435) from one medical centre between 1988 and 1998 in Taiwan. Sixty oral carcinomas were ascertained in this cohort. A case-control study within the leukoplakia cohort was used to study, risk factors. Using the Weibull survival model, the incidence of malignant trans formation of leukoplakia was shown to increase with follow-up years. After adjustment for other relevant risk factors, betel nut chewing (adjusted odd s ratio (OR) = 4.59; 95% confidence interval (CI) 1.25-16.86) remained a si gnificant risk factor for malignant transformation. Results from the case-c ontrol study showed that the adjusted odds ratios for betel nut chewing and smoking on the occurrence of leukoplakia were 17.43 (95% CI 1.94-156.27) a nd 3.22 (95% CI 1.06-9.78), respectively. Similar findings were observed wh en daily frequency and duration were taken into account. This implies that cessation of smoking may reduce by 36% leukoplakia cases, while elimination of betel nuts may prevent 62% of leukoplakia and 26% of malignant transfor mation to oral carcinoma in the underlying population. (C) 2000 Cancer Rese arch Campaign.