Malignant transformation of oral submucous fibrosis in Taiwan: A nationwide population‐based retrospective cohort study

Background Oral submucous fibrosis ( OSF ) is one of the well‐recognized oral potentially malignant disorders. In this study, we investigated the malignant transformation of OSF in a 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 OSF cohort according to age, sex, and index year. Oral leukoplakia ( OL ) was further stratified to evaluate for the possible synergistic effects of OSF ‐associated malignant transformation. Results In this cohort, 71 (9.13%) of 778 cases of OSF were observed to transform into oral cancer. The malignant transformation rate was 29.26‐fold in the OSF cohort than in the comparison cohort after adjustment (95% confidence intervals 20.55‐41.67). To further stratify with OL, OSF with OL (52.46%; 95% confidence intervals 34.88‐78.91) had higher risk of malignant transformation rate than OSF alone (29.84%; 95% confidence intervals 20.99‐42.42). The Kaplan‐Meier plot revealed the rate free of malignant transformation was significant over the 13‐year follow‐up period (log‐rank test, P <.001). The mean duration of malignant transformation was 5.1, 2.7, and 2.2 years for non‐ OSF , OSF alone, and OSF with OL , respectively. Conclusion Oral submucous fibrosis patients exhibited a significantly higher risk of malignant transformation than those without OSF . OL could enhance malignant transformation in patients with OSF .