Discrimination of normal and malignant stomach mucosal tissues by Raman spectroscopy: A pilot study

Stomach cancers are the fourth most common cancers and second most common cause of death from cancers worldwide. Two thirds of cases are reported from the developing world. The identified risk factors are consumption of traditionally salted meat or pickles, tobacco smoking and Helicobacter pylori infection. High intake of fruits and vegetables has shown to decrease the risk. Endoscopy with histopathology is the diagnostic investigation. Radical gastrectomy is the treatment of choice. Prognosis depends on the stage at the time of diagnosis. Conventional Raman spectroscopic studies of normal and malignant stomach tissues are carried out. The aim of the study is to explore the feasibility of discriminating these tissues. The mean Raman spectra of normal and malignant tissues exhibit significant differences in amide I, ΔCH₂ and amide III region. The major spectral features of normal tissue with respect to malignant tissue are: weak amide I, slightly red shifted ΔCH₂, an intense band at 1303 cm^-1 and a hump at 1276 cm^-1. Multivariate statistical tool, principal components analysis (PCA) is employed for developing discrimination methods. Scores of factors, Mahalanobis distance and spectral residuals are used as discriminating parameters. This approach is tested both retrospectively and prospectively. The analysis is further fine-tuned by employing 'Limit test' approach wherein reasonable discrimination between two groups, normal and malignant is observed for Mahalanobis distance of '3'. The results obtained in this pilot study indicate the feasibility of discriminating normal and malignant stomach mucosal tissues by Raman spectroscopy.