Fecal microbial markers–the role in colorectal cancer screening: a review of literature

Abstract

Introduction. Colorectal cancer (CRC) is the third most common cancer worldwide, accounting for about 10% of all cancer cases diagnosed annually. Due to the high prevalence of CRC, implementation of a screening program, especially non-invasive would reduce the incidence by eradicating precancerous lesions, as well as mortality by treating the early stages of the disease. Aim of the study. Presentation of recent information on the role of fecal microbial markers as a non-invasive method in the early detection of CRC. Materials and methods.. 47 literary sources were analyzed, using Medline, PubMed, Google Scholar, Hindawi databases over a 5 year period. Keywords used in the search: microbial markers, screening, colorectal cancer. Results. Of the 47 articles selected: 16–dedicated to clinical diagnostic methods, 10–regarding the fecal immunochemical test (FIT), 11–regarding the role of fecal microbial markers in combination with FIT, as predictors of CRC and 10–regarding the specificity and sensitivity of the markers fecal microbes in symptomatic and asymptomatic patients. Thus, it was determined that certain bacterial species, such as Parvimonas micra, Solobacterium moorei, and Clostridium hathewayi, are significantly enriched in stool samples from CRC patients, whereas the presence of other bacterial species, such as Bacteroides clarus and Roseburia intestinalis, is significantly reduced in CRC patient stool. Also, Fusobacterium nucleatum is thought to potentiate intestinal tumorigenesis through recruitment of infiltrating immune cells and via activation of beta-catenin signaling. Such increased or decreased presence of these bacterial species results in higher or lower levels of signature DNA, RNA and protein species unique to these species, witch in turn can be used for detection, both qualitatively and quantitatively. Conclusions. This review highlights the effectiveness of non-invasive methods in the early diagnosis of CRC, in estimating the risk of relapse and neoplastic dissemination, as well as the rate of response to adjuvant treatment. Implementing an effective screening program would reduce mortality in CRC, save a significant portion of the resources that would be spent on treating patients in advanced stages of the disease.