Ex Vivo Vibration Spectroscopic Analysis of Colorectal Polyps for the Early Diagnosis of Colorectal Carcinoma

Abstract

Colorectal cancer is one of the most common and often fatal cancers in humans, but it has the highest chance of a cure if detected at an early precancerous stage. Carcinogenesis in the colon begins as an uncontrolled growth forming polyps. Some of these polyps can finally be converted to colon cancer. Early diagnosis of adenomatous polyps is the main approach for screening and preventing colorectal cancer, and vibration spectroscopy can be used for this purpose. This work is focused on evaluating FTIR and Raman spectroscopy as a tool in the ex vivo analysis of colorectal polyps, which could be important for the early diagnosis of colorectal carcinoma. Multivariate analyses (PCA and LDA) were used to assist the spectroscopic discrimination of normal colon tissue, as well as benign and malignant colon polyps. The spectra demonstrated evident differences in the characteristic bands of the main tissue constituents, i.e., proteins, nucleic acids, lipids, polysaccharides, etc. Suitable models for discriminating the three mentioned diagnostic groups were proposed based on multivariate analyses of the spectroscopic data. LDA classification was especially successful in the case of a combined set of 55 variables from the FTIR, FT Raman and dispersion Raman spectra. This model can be proposed for ex vivo colorectal cancer diagnostics in combination with the colonoscopic extraction of colon polyps for further testing. This pilot study is a precursor for the further evaluation of the diagnostic potential for the simultaneous in vivo application of colonoscopic Raman probes.

Comparative Study on Handheld, Modular, and Laboratory Raman Instruments for the Analysis of Colon Tissues and Colorectal Polyps

“…The above bands, showing significant differences between samples, can be offered as potential markers of carcinogenesis in colon tissue. The spectra of normal colon tissue have a number of bands characteristic of the main biochemical components: proteins (including collagens), lipids, nucleic acids, and polysaccharides [5,6,[43][44][45][46][47][48][49][50]. In addition, many bands include contributions from several biochemical components, making their assignment difficult.…”

“…These two bands arise mainly from the purine ring breathing vibrations [29,30], and the C-S stretching vibration of cysteine (Cys) contributes to the first one [31][32][33]. Thus, the observed spectral differences between normal colon tissue and benign and malignant polyps, which can be associated with colorectal cancer development, indicate changes in the ratio between such major biochemical tissue components as proteins, nucleic acids, lipids, and polysaccharides [44][45][46][47]50]. The above bands, showing significant differences between samples, can be offered as potential markers of carcinogenesis in colon tissue.…”

“…This goal can be achieved by comparing individual characteristic Raman bands of biochemical markers of carcinogenesis or through the discriminatory analysis of Raman spectra using multivariate statistical methods. Previous works have used various approaches to separate and classify normal and pathological tissue and biofluid samples based on Raman spectra, such as HCA [6,43], PCA [40], partial least squares discriminant analysis (PLS-DA) [51,52], SVM and other machine learning methods [43], PCA in combination with linear discriminant analysis (LDA), SVM, SIMCA [53] and other discriminating parameters like Mahalanobis distance or spectral residuals [45,52,[54][55][56][57], and convolutional neural networks (CNN) [58][59][60][61]. Of particular interest for early cancer diagnosis is the immediate analysis of intracellular Raman spectra using a biomolecular component analysis (BCA) algorithm [62].…”

In vivo Raman spectroscopy in the diagnostics of colon cancer

“…Raman spectroscopy was found to be effective in tissue diagnostics of colorectal cancer in studies focusing on ex vivo samples, 11–16 while others aimed to turn to in vivo analyses and succeeded in testing specialized optical fiber systems. 17–19…”

“…Raman spectroscopy was found to be effective in tissue diagnostics of colorectal cancer in studies focusing on ex vivo samples, [11][12][13][14][15][16] while others aimed to turn to in vivo analyses and succeeded in testing specialized optical fiber systems. [17][18][19] The first use of an in vivo Raman probe to diagnose precancerous colonic polyps showed 95% accuracy on a set of 19 patients.…”