Circulating free DNA concentration as a marker of disease recurrence and metastatic potential in lung cancer

Background: Plasma circulating cell-free (cf) DNA is regarded as a source of tumor DNA. Based on availability of blood tissue for the purposes of early detection of cancer and patients' follow-up, several studies have evaluated concentration of cf DNA in cancer patients in association with tumor features. In the present study, we assessed concentration of cf DNA in lung cancer patients with two commercial kits (MN and QIAGEN) to find whether it can be used as a prognostic biomarker. Results: Primary cf DNA concentrations as measured by QIAGEN kit was significantly higher in patients who died in the follow-up period compared with alive patients (P=0.007). Moreover, the concentrations as measured by both methods were higher in patients who experienced recurrence in the follow-up period compared with patients without recurrence (P=0.008 and 0.007 for MN and QIAGEN kits respectively). Significant associations were also found between cf DNA concentrations and tumor stage (P=0.005 and 0.02 for MN and QIAGEN kits respectively). Notably, cf DNA concentration was higher in metastatic tumors compared with non-metastatic tumors in association with number of involved organs. Based on the AUC values, both kits could differentiate metastatic cancers from non-metastatic ones with accuracy of 98%. Conclusions: The current study highlights the accuracy of cf DNA concentrations for prediction of disease course in lung cancer patients.