Diagnostic Accuracy of Salivary DNA Integrity Index in Oral Malignant and Premalignant Lesions

As stated by the U.S. Preventive Services Task Force and the National Institute of Dental and Craniofacial Research, the main screening test for oral cancer remains conventional oral examination of the oral cavity. Most cases of oral cancer are preceded by a clinically visible lesion. These lesions are called oral potentially malignant disorders. These are leukoplakia, erythroplakia, oral submucous fibrosis, oral lichen planus and discoid lupus erythematosis. Leukoplakia has a reported annual transformation rate of 2-3%, while OLP has a rate of 0.5% .

Full thickness tissue biopsy is the "gold standard" for diagnosing suspicious lesions should they be encountered during COE. However, oral biopsy is an invasive technique that can be challenging in sites as the floor of the mouth or the soft palate . The invasive nature of a biopsy also makes it unsuitable for cancer screening in high-risk populations.

Thus there is a need for a diagnostic aid that can help primary care providers determine which patients need to be biopsied or referred to a specialist.

Nucleic acids can be released actively or passively into the circulation by both living and dead cells, where the latter is considered the predominant source. Programmed cell death gives neatly digested DNA fragments of approximately 180 bp in length. In case of solid tumors, cell-free DNA is released through necrosis which generates longer DNA fragments due to haphazard and incomplete digestion of DNA. Thus, the integrity of the DNA fragment can determine its origin making DNA integrity a potential marker for oral cancer.

The DNA integrity index (DII) is the ratio between the longer DNA fragments to the shorter ones. A higher index has been reported in breast, prostate, liver and cervical cancer. Jiang et al. 2006 found that the DNA integrity index was significantly higher in oral cancer patients than in normal ones and reported a sensitivity and specificity values of 84.5% 83% respectively . The next step for such a marker would be early quantification of performance in clinical settings to determine if it is possible to extrapolate cut off values.