METHODS: Sections from diagnostic biopsies were assessed for oral epithelial dysplasia using the WHO grading system, and DNA ploidy analysis was performed using established methods. Patients reviewed for a minimum of 5 years who did not develop oral squamous cell carcinoma were classified as "non-transforming" cases. Patients that developed oral squamous cell carcinoma ≥ 6 months after the initial diagnostic biopsy were classified as having "malignant transformation."

METHODS: The study was initiated in September 2005 and patients were followed up to March 2014. Two hundred patients with oral leukoplakia, 100 patients with oral cancer and 100 healthy, age and sex matched adults with normal oral mucosa as controls were recruited. The DNA ploidy content was measured by high resolution flow cytometry, level of telomerase expression was identified by TRAP assay and intrinsic DNA repair capacity was measured by mutagen induced chromosome sensitivity assay of cultured peripheral blood lymphocytes. The Chi-square test or Fisher's Exact test was used for comparison of categorical variables between biomarkers. A p value less than or equal to 0.05 was considered as statistically significant. Analysis was performed with SPSS software version 16. Logistic regression was used to find the association between the dependent and three independent variables.