Raman spectroscopy and cytopathology of oral exfoliated cells for oral cancer diagnosis

For oral cancers, screening and monitoring of high-risk populations can aid in early diagnosis and improve overall outcomes. Of the new methods, approaches based on exfoliative cytology are more practical for mass screening and monitoring of high-risk populations. Raman spectroscopy and exfoliative cytology for cervical cancers have shown promise in differentiating normal and abnormal samples. In this study, the feasibility of Raman oral exfoliative cytology along with cytopathology for oral cancer diagnosis was evaluated in 70 specimens. Exfoliated cells were obtained from 15 healthy volunteers (HV), 15 healthy tobacco users (HT), and 20 contralateral or disease control (DC) and 20 tumor (T) sites of same oral-cancer patients. Pap staining was carried out post Raman spectral acquisition. Spectral findings demonstrate that with increase in severity of pathology from HV to T, higher DNA and changes in secondary structure of proteins were encountered. Owing to heterogeneity in cellular samples, two different approaches - point-spectra and patient-wise - were evaluated for data analysis. PCA and PC-LDA using both approaches indicate that HV and HT are distinct from cancer groups DC and T. Misclassifications were also observed between HT and DC. These findings also correlate with cytopathological findings. Fewer misclassifications and higher classification efficiency were observed for the patient-wise approach. A large-scale validation study needs to be undertaken for evaluating the utility of Raman oral exfoliative cytology for screening of oral cancers using the patient-wise approach.