Lung cancer is the most frequently diagnosed tumour type and the leading cause of cancer mortality throughout the world. The prognosis of patients is strongly correlated with tumour stage,1 hence the importance of an accurate, easily usable diagnostic tool for early detection.

Low-dose spiral computed tomography (CT) has opened up interesting prospects for early diagnosis but is expensive, invasive and presents some limitations, especially in terms of specificity.2 Free circulating DNA levels have been shown to be higher in patients with lung cancer than in healthy individuals (including heavy smokers), suggesting that this marker could be an important tool to identify lung cancer in screening programmes.3 More recently, our group4 and other researchers5 have shown that plasma or serum free DNA is also significantly higher in patients with other cancer histotypes than in healthy donors. …