Molecular assessment of former cancer sites predicts second oral malignancy

Clinicopathological criteria currently used to identify lesions at risk for second oral malignancy (SOM) have severe limitations. This thesis investigated the value of loss of heterozygosity (LOH) as a risk-predictor for SOM. Eighty-nine patiknts with a history of oral cancer in longitudinal follow-up were used. Each patient had one sample (biopsy or brushing) analyzed for LOH using 19 markers on 7 chromosome arms. Within the follow-up period (mean 65 months), 28% developed SOMs. Brushing served as a valid DNA source for LOH analysis. An increased frequency of LOH observed at several loci was noted in samples from the SOM group compared with the non-SOM: 3p (P = 0.003), 4q (P = 0.045), 9p (P < 0.0001), 17p (P = 0.001), multiple LOH (P < 0.0001), and LOH at 3p &/or 9p (P < 0.0001). The latter pattern was associated with a 21.4-fold increase in SOM risk. In conclusion, LOH analysis could identify high-risk lesions for SOM using either biopsies or brushings.