Fourier-transform infrared spectrometric analysis for detecting colorectal carcinoma

OBJECTIVE: To assess the value of Fourier-transform infrared (FT-IR) spectroscopic analysis in detecting colorectal carcinoma. METHODS: Fifty pairs of specimens of exfoliated cells from patients with colorectal carcinoma, who had undergone colorectal resection, were analyzed by using FT-IR spectrometry. Exfoliated cells were obtained by scraping off: (i) the foci of the colorectal carcinoma; and (ii) the normal mucosa more than 5 cm away from the foci. Cell specimens were fixed and smeared onto two slides: a gold-coated slide for the infrared spectrometry and a conventional one for histopathological evaluation. The spectra from 28 pairs of specimens were analyzed by logistic regression with multiple factors to establish a statistical model for predicting the probability of colorectal cancers, and then the spectra of the remaining 22 pairs were judged according to the model. Their corresponding diagnostic accuracy was calculated. RESULTS: Substantial differences were found in the spectral properties of cancer and non-cancer cells, which were evident in the frequency region of 1000–1350/cm. A shift of the phosphodiester groups of nucleic acids was noted: compared with the spectral features of non-cancerous cells, the distance between VsPO2– and VasPO2– was shorter in cancerous cells. The C–O stretching bonds of cell proteins were significantly changed in the frequency region of 1140–1180/cm. In non-cancerous cells, the peak intensity of 1155/cm was stronger than that of 1174/cm, whereas in cancerous cells the peak intensity of 1155/cm was weaker than that of 1174/cm; the peak intensity ratio of 1174/cm : 1155/cm was increased in cancerous cells. The spectral characteristics of the spectrometric data from the 22 pairs of specimens were consistent with those of the base-model data. The other 22 pairs of specimens were analyzed according to the model, indicating that Fourier-transform infrared spectrometry can be used to discriminate cancerous cells from non-cancerous cells with a sensitivity of 90.91%, a specificity of 86.36%, a positive prediction value of 86.96% and a negative predictive value of 90.48%. CONCLUSIONS: Fourier-transform infrared spectrometry is of value in detecting colorectal cancer cells and it could be used as a rapid method for the clinical screening of malignant cells.