Circulating DNA is a non-invasive prognostic factor for survival in non-small cell lung cancer

IntroductionCirculating plasma DNA is present in a considerably higher concentration in lung cancer patients than in controls. Conflicting data are reported about circulating DNA as a prognostic factor. The aim of this study was to prospectively analyse the relationship of circulating plasma DNA with overall survival (OS) of previously untreated non-small cell lung cancer (NSCLC) patients.Methods46 untreated NSCLC patients and 21 controls with a follow-up time of 6.5 years were analyzed. Quantification of baseline circulating plasma DNA was performed by a real-time quantitative polymerase chain reaction (qPCR) targeting the human β-globin gene. Survival analysis was performed using the Kaplan–Meier method and compared with a Cox-regression analysis.ResultsThe median DNA concentration of the patients who died (87%) was significantly higher compared to the patients that survived at the end of follow-up (55 ng/ml versus 23 ng/ml, p = 0.02). In patients with higher DNA concentration overall survival was significantly worse. In this study no relation of DNA concentration with tumour characteristics, age, gender or pulmonary inflammatory conditions was found.ConclusionIn this study a high circulating plasma DNA concentration at time of diagnosis in NSCLC patients was a prognostic factor for poorer survival. Circulating DNA may be used as a non-invasive biomarker to refine the prognostic profile in NSCLC patients.