Malignant transformation of Taiwanese patients with oral leukoplakia: A nationwide population-based retrospective cohort study

Background/Purpose: Oral leukoplakia (OL) is one of the clinically diagnosed oral potentially malignant disorders (OPMDs) with an increased risk of oral cancer development. In this study, we investigated the malignant transformation of OL in Taiwanese population. Methods: A retrospective cohort study was analyzed from Taiwan's National Health Insurance Research Database. A comparison cohort was randomly frequency-matched with the OL cohort according to age, sex, and index year. Oral submucous fibrosis (OSF) and oral lichen planus (OLP) were further stratified to evaluate the possible synergistic effects for OL-associated malignant transformation. Results: In this cohort, 102 (5.374%) of 1898 OL patients were observed to transform into oral cancer. The malignant transformation rate was 26.40-fold in the OL cohort than in the comparison cohort after adjustment (95% confidence intervals 18.46–37.77). To further stratify with OSF and OLP, OL with OSF (58.38; 95% confidence intervals 34.61–98.50) and OL with OLP (36.88; 95% confidence intervals 8.90–152.78) had higher risk of malignant transformation rate than OL alone (27.01; 95% confidence intervals 18.91–38.59). The Kaplan–Meier plot revealed the free of malignant transformation rate was significant over the 13 years follow-up period (log-rank test, p < 0.001). Conclusion: OL patients exhibited a significantly higher risk of malignant transformation than those without OL. In addition, both OSF and OLP could enhance malignant transformation in patients with OL. However, further studies are required to identify the histopathological and clinical parameters in the pathogenesis of malignant transformation among OPMDs. Keywords: Oral leukoplakia, Oral submucous fibrosis, Oral lichen planus, Malignant transformation, Nationwide population, Cohort study, Taiwa