Real-time polymerase chain reaction quantification of free DNA in serum of patients with polyps and colorectal cancers

Background: Colorectal cancer (CRC) is one of the most frequent causes of cancer related deaths worldwide. Recently, the use of cell-free DNA as diagnostic tools to identify cancer has been investigated. The aim of this work was to assess whether circulating DNA could be considered a useful marker for detection of early stage CRC and polyps. Methods: A total of 118 patients with CRC were included in the study along with 49 patients with colorectal polyps and 26 control subjects. Cell-free DNA was quantified using a real-time TaqMan-polymerase chain reaction assay. Nonparametric tests (Mann-Whitney test and Spearman correlation) were utilized for statistical analysis. Results: Serum DNA concentrations were significantly higher in CRC patients and patients with polyps (median value 105.0 ng/mL and 40.0 ng/mL) compared with controls (median value 14.0 ng/mL; p<0.05). Although carcinoembryonic antigen was above the cut-off in only 13/66 (19.7%) patients with early stage CRC, serum free DNA showed values above the threshold identified using receiver operator characteristic (ROC) curve analysis in 53/66 (80.3%) patients. Conclusions: Our data confirm that serum DNA concentrations are significantly increased in CRC patients with early stage disease and in patients with polyps. This marker might be useful for identifying high-risk individuals. Clin Chem Lab Med 2010;48:1665-8.