Stool DNA methylation assays in colorectal cancer screening.

Colorectal cancer (CRC) is fourth most common cancer in men and third in women worldwide. Developing a diagnostic panel of sensitive and specific biomarkers for the early detection of CRC is recognised as to be crucial for early initial diagnosis, which in turn leads to better long term survival. Most of the research on novel potential CRC biomarkers in the last 2 decades has been focussed on stool DNA analysis. In this paper, we describe the recent advances in non-invasive CRC screening and more specifically in molecular assays for aberrantly methylated BMP3 and NDRG4 promoter regions. In several research papers these markers showed superior rates for sensitivity and specificity in comparison to previously described assays. These tests detected the majority of adenomas ≥ 1 cm in size and the detection rates progressively increased with larger adenomas. The methylation status of the BMP3 and NDRG4 promoters demonstrated effective detection of neoplasms at all sites throughout the colon and was not affected by common clinical variables. Recently, a multitarget stool DNA test consisting of molecular assays for aberrantly methylated BMP3 and NDRG4 promoter regions, mutant KRAS and immunochemical assay for human haemoglobin has been made commercially available and is currently reimbursed in the United States. Although this is the most sensitive non-invasive CRC screening test, there is the need for further research in several areas - establishment of the best timeframe for repeated DNA stool testing; validation of the results in populations outside of North America; usefulness for surveillance and prognosis of patients; cost-effectiveness of DNA stool testing in real-life populations.