Detection of circulating tumour cells in colorectal cancer: Emerging techniques and clinical implications

Abstract

Despite several advances in oncological management of colorectal cancer, morbidity and mortality are still high and devastating. The diagnostic evaluation by endoscopy is cumbersome, which is uncomfortable to many. Because of the intra- and inter-tumour heterogeneity and changing tumour dynamics, which is continuous in nature, the diagnostic biopsy and assessment of the pathological sample are difficult and also not adequate. Late manifestation of the disease and delayed diagnosis may lead to relapse or metastases. One of the keys to improving the outcome is early detection of cancer, ease of technology to detect with uniformity, and its therapeutic implications, which are yet to come. "Liquid biopsy" is currently the most recent area of interest in oncology, which may provide important tools regarding the characterization of the primary tumour and its metastasis as cancer cells shed into the bloodstream even at the early stages of the disease. By using this approach, clinicians may be able to find out information about the tumour at a given time. Any of the following three types of sampling of biological material can be used in the "liquid biopsy". These are circulating tumour cells (CTCs), circulating tumour DNA, and exosomes. The most commonly studied amongst the three is CTCs. CTCs with their different applications and prognostic value has been found useful in colorectal cancer detection and therapeutics. In this review, we will discuss various markers for CTCs, the core tools/techniques for detection, and also important findings of clinical studies in colorectal cancer and its clinical implications.

Keywords: Circulating tumour cells; Colorectal cancer; Tools and techniques; Clinical implications

Core Tip: Circulating tumour cells (CTCs) in the blood have been found to be mainly associated with the stage of the disease and serve as a prognostic marker for survival in colorectal cancer. Some studies have also reported its role in the diagnosis and treatment monitoring. By focusing molecular research on rare CTCs, targeting cellular markers of CTCs, and discovering new cellular markers may improve the management of colorectal cancer and play a role in prevention of metastatic disease. Patients at high risk might benefit from additional individualized treatment which can be investigated in future clinical trials.