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

<jats:sec><jats:title>Background</jats:title><jats:p>Oral submucous fibrosis (<jats:styled-content style="fixed-case">OSF</jats:styled-content>) is one of the well‐recognized oral potentially malignant disorders. In this study, we investigated the malignant transformation of <jats:styled-content style="fixed-case">OSF</jats:styled-content> in a Taiwanese population.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>A retrospective cohort study was analyzed from Taiwan's National Health Insurance Research Database. A comparison cohort was randomly frequency‐matched with the <jats:styled-content style="fixed-case">OSF</jats:styled-content> cohort according to age, sex, and index year. Oral leukoplakia (<jats:styled-content style="fixed-case">OL</jats:styled-content>) was further stratified to evaluate for the possible synergistic effects of <jats:styled-content style="fixed-case">OSF</jats:styled-content>‐associated malignant transformation.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>In this cohort, 71 (9.13%) of 778 cases of <jats:styled-content style="fixed-case">OSF</jats:styled-content> were observed to transform into oral cancer. The malignant transformation rate was 29.26‐fold in the <jats:styled-content style="fixed-case">OSF</jats:styled-content> cohort than in the comparison cohort after adjustment (95% confidence intervals 20.55‐41.67). To further stratify with OL, <jats:styled-content style="fixed-case">OSF</jats:styled-content> with <jats:styled-content style="fixed-case">OL</jats:styled-content> (52.46%; 95% confidence intervals 34.88‐78.91) had higher risk of malignant transformation rate than <jats:styled-content style="fixed-case">OSF</jats:styled-content> 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, <jats:italic>P</jats:italic><.001). The mean duration of malignant transformation was 5.1, 2.7, and 2.2 years for non‐<jats:styled-content style="fixed-case">OSF</jats:styled-content>,<jats:styled-content style="fixed-case"> OSF</jats:styled-content> alone, and <jats:styled-content style="fixed-case">OSF</jats:styled-content> with <jats:styled-content style="fixed-case">OL</jats:styled-content>, respectively.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>Oral submucous fibrosis patients exhibited a significantly higher risk of malignant transformation than those without <jats:styled-content style="fixed-case">OSF</jats:styled-content>. <jats:styled-content style="fixed-case">OL</jats:styled-content> could enhance malignant transformation in patients with <jats:styled-content style="fixed-case">OSF</jats:styled-content>.</jats:p></jats:sec>