Cell-free circulating tumor DNA in colorectal cancer: a proof of concept with simplified methodology

Cell-free DNA analysis (cfDNA) holds promise for residual disease or tumor burden quantification in colorectal cancer, with reduced costs and diagnostic equipment compared to gold standard-specific tumor DNA (ctDNA) analysis.

This prospective case-control study included 46 colorectal cancer patients and healthy controls to perform cfDNA quantification by fluorometry using Quantus Fluorometer (Promega, Madison, WI) and using cell-free DNA ScreenTape assay (Agilent) and 4200 TapeStation instrument (Agilent Technologies, Inc., Santa Clara, CA, USA). cfDNA quantification results were correlated with stage, clinical and histopathological features.

33 localized (8 stage I, 12 stage II, and 13 stage III) and 13 advanced colorectal cancer patients were included. No differences in cfDNA quantification by fluorometry were demonstrated depending on stage or histopathological features in localized disease patients. Differences in cfDNA quantification by fluorometry could be demonstrated in patients with advanced disease depending on the presence of liver metastases and synchronous or metachronous metastatic disease. Differences in cfDNA quantification by fluorometry could be demonstrated between advanced colorectal cancer patients and both localized disease patients and healthy controls. Secondary cfDNA analysis by electrophoresis, although showing more specificity to measure ctDNA in cfDNA values, could not improve the capacity to detect differences between analyzed a groups beyond previously achieved with fluorometry.

This exploratory analysis of cfDNA based on fluorometry and electrophoresis methods showed promising results discriminating colorectal cancer and non-cancer patients, as well as different colorectal cancer stages and disease profiles. Further studies are needed to increase our knowledge and to help to overcome barriers to broader implementation and applications.