Quantitative analysis of plasma DNA in colorectal cancer patients - A novel prognostic tool

Extracellular DNA in the plasma or serum of cancer patients has been recently proposed as a source of analyzable cancer-related gene sequences (qualitative approach). Furthermore, patients with different tumor types show high levels of cell-free circulating DNA both in plasma and serum (quantitative approach) at the time of surgery. Our aim was to verify whether the level of cell-free DNA in plasma might help in detecting recurrences during follow-up of colorectal cancer (CRC) patients. We studied 70 patients undergoing surgery for primary CRC. Plasma samples were obtained at the time of surgery and during follow-up. The cell-free circulating DNA in plasma was quantified by the Dipstick Kit method. At the time of surgery, in all patients, cell-free DNA levels in plasma were about 25 times higher in comparison with 20 healthy donors. In contrast, the carcinoembryonic antigen (CEA) value of this cohort of patients was altered in only about 37% of cases. During follow-up, cell-free DNA levels decreased progressively in tumor-free patients, while it increased in those developing recurrences or metastases.