Quantitative analysis of free-circulating DNA in plasma of patients with resectable NSCLC

Objective: Minute amounts of free-circulating DNA are present in plasma of healthy individuals, whereas its increased concentration was observed in patients with malignant tumors including non-small cell lung cancer (NSCLC). This study aimed at demonstrating the potential usefulness of plasma DNA concentration monitoring in NSCLC patients for therapy effectiveness assessment throughout the treatment and follow-up period. Methods: Plasma DNA concentration was assessed in 50 NSCLC patients (stage I - IIIA) prior and following the radical treatment using real-time quantitative PCR method. 10 orthopedic patient undergoing hip joint surgery and 40 healthy volunteers comprised control groups. Results: NSCLC patients (8.02 ng/ml) demonstrated significantly higher mean plasma DNA concentration with respect to healthy controls (2.27 ng/ml; p < 0.0000). Drastic increase in plasma DNA levels up to mean 68.74 ng/ml was detected a week after primary tumor resection. Still, similar phenomenon was observed in patients subjected to orthopedic surgical treatment (from 3.00 to 28.38 ng/ml, p < 0.0015). Most resected NSCLC patients with no disease recurrence during 3- to 6-month follow-up demonstrated reduced plasma DNA levels (mean 2.77 ng/ml) with respect to their presurgical values, whereas in relapsed subjects plasma DNA levels were significant higher. Conclusion: Free-circulating DNA concentration in plasma was significantly higher in NSCLC patients versus healthy controls. Its drastic increase following radical NSCLC treatment was most likely due to the surgical trauma. Importantly, the kinetics of plasma free-circulating DNA seems to be a promising marker of long-term effects of radical surgery in NSCLC.