Malignant transformation of oral leukoplakia and associated risk factors: A retrospective clinical study from a single institution

This study investigated the clinical features of oral leukoplakia (OL) and its rate of progression to oral squamous cell carcinoma (OSCC) in a Japanese population. We also investigated the impact of clinical risk factors on the rate of malignant transformation (MT). This retrospective study included 308 patients diagnosed with OL between 1989 and 2020. Of these, 231 patients with 6 months follow-up were enrolled. The Kaplan−Meier method was employed to analyze 5- and 10-year risks of developing OSCC. Chi-square test and nominal logistic regression analysis were used to investigate predictors of progression to OSCC. The mean age of the patients was 62.6 years (range 20 −89), and 45.9 % were female. The most common site of OL was the tongue (36.4 %). Twenty patients (8.7 %) experienced MT to OSCC. The predominant clinical type was the homogenous type (66.7 %), with no patient developing OSCC. Univariate analyses showed that the risk of progression to OSCC was significantly higher in patients aged < 64 years, those with OL of the tongue, nonhomogeneous type, and biopsied cases. In the multivariate analyses, the statistically significant predictor was clinical type. The numbers of female nonsmokers and nondrinkers were significantly higher among the MT cases (p = 0.0016, p = 0.0373, respectively). OL increases the risk of MT due to a combination of clinical risk factors. Therefore, high-risk cases require shorter follow-up intervals, and we suggest that multiple examiners share their findings. Performing biopsies to identify histopathological factors and make a definitive diagnosis should be considered.