Diagnostic Value Of Confocal Raman Spectroscopy For Colorectal Cancer

Background and purpose:Colorectal cancer(CRC)is one of the most common malignancies in the world.It’s morbidity and mortality incidence is ranked third and second respectively among all malignancies.Currently,the diagnosis of CRC mainly relies on colonoscopy combined with the histopathological examination and lacks of an early,rapid and non-invasive screening technique.Raman spectroscopy is an inelastic light scattering technique that is capable of providing specific spectroscopic fingerprints of molecular compositions and structures of biological tissues.It can efficiently detect the subtle changes in the structure of the material accurately,reflecting the biochemical information changes in the process of carcinogenesis and has a high clinical application value.Currently,Raman spectroscopy has been used for the diagnosis of malignancies,but there are few reports on its application in CRC.Based on clinical requirements,this study used confocal Raman spectroscopy to analyze the spectral characteristics of colorectal tissue.,Observing the difference in spectral characteristics during colorectal tissue transforms into cancer,exploring the application value of Raman spectroscopy for diagnosing CRC.Methods:This study evaluated 71 patients who underwent an electronic colonoscopy and histopathological examination from May 20th to November 2018 in Zhujiang Hospital of Southern Medical University.A total of 80 cases of Colorectal tissues ex vivo was identified into three groups,including normal colorectal tissue(15 cases)、adenomatous polyps(40 cases)and colorectal adenocarcinoma tissues(25 cases)by using pathological staining.The Raman spectrum of each colorectal tissue was collected by confocal Raman spectroscopy.Statistical analysis was performed on the Spectral data by one-way analysis of variance(ANOVA),principal component analysis(PCA),Fisher discriminant analysis,and partial least squares discriminant analysis(PLS-DA).The advantages and disadvantages of Fisher discriminant analysis and partial least squares discriminant analysis(PLS-DA)in the diagnosis of CRC were compared,and the ROC curve was used to evaluate diagnostic efficiency.In addition,the PLS-DA algorithm is used to distinguish between adenomatous polyps and tumor tissues of different stages,to evaluate the early diagnostic value of Raman spectroscopy in colorectal cancer.Results:By using Fisher discriminant analysis combined with Leave one out cross validation to identify colorectal tissues,The results showed that the sensitivity,specificity,and accuracy of the normal group were 88.17%、98.43%、96.41%,respectively;The sensitivity,specificity,and accuracy of the adenoma group were 85.15%,82.45%,and 83.76%,respectively.The sensitivity,specificity,and accuracy of the adenocarcinoma group were 74.34%,89.13%,and 84.39%,respectively.The AUC of the normal group,adenoma group,and adenocarcinoma group were 0.9919,0.9881,and 0.8808,respectively.By using partial least squares discrimination analysis(PLS-DA)to distinguish colorectal tissues,the results showed that the sensitivity,specificity,accuracy,and AUC of the normal group and the adenoma group were 100%、87.39%,90.80%,and 0.9936,respectively.The sensitivity,specificity,accuracy,and AUC of the normal group and adenocarcinoma group were 96.59%,91.89%,93.64%,and 0.9840,respectively.The sensitivity,specificity,accuracy,and AUC of the colorectal tissues of the adenoma group and the adenocarcinoma group were 91.22%、78.57%、83.42%、0.9266,respectively.By using partial least squares discrimination analysis(PLS-DA)to distinguish between adenomatous polyps and tumor tissues of different stages,the results showed that the sensitivity,specificity,accuracy,and AUC of adenoma group and TNM stage I colorectal cancer were 68.07%,98.15%,73.63%and 0.9440,respectively.The sensitivity,specificity,accuracy,and AUC of TNM stage I and TNM Ⅱ+Ⅲ+Ⅳcolorectal cancer were 75.93%,71.28%,72.97%and 0.8383,respectively.Conclusion:(1)By analyzing and comparing the Raman spectra of colorectal tissues with different pathological types,it was found that the composition and content of colorectal tissues,in the process of carcinogenesis,has changed significantly at the molecular level:The relative intensity of the Raman peak of the adenocarcinoma group at 758 cm-1 was significantly stronger than that of the normal group and the adenoma group,it suggesting that the proliferation of colorectal adenocarcinoma was active and the expression of tryptophan increased.The relative intensity of the Raman peak in the normal group at 1156 cm-1 was significantly stronger than that in the adenoma group and the adenocarcinoma group suggesting that in the colorectal cancer,the content of anti-tumor substances such as B-carotene decreased.(2)Confocal Raman spectroscopy combined with PLS-DA or Fisher-discriminant analysis for the determination of normal colorectal tissue,colorectal adenomatous polyps,colorectal cancer tissue has a very high diagnostic efficiency;The PLS-DA method is slightly better than Fisher-discriminant analysis in the discrimination of colorectal adenomatous polyps and colorectal cancer tissues;Confocal Raman spectroscopy has a high diagnostic efficacy in the diagnosis of colorectal adenoma,TNM stage Ⅰ colorectal cancer,and TNM stage Ⅱ+Ⅲ+Ⅳcolorectal cancer.