Cell-free DNA concentration in pleural fluid and serum: quantitative approach and potential prognostic factor in...

The presence of pleural effusions in patients with tumors is often indicative of locally advanced or metastatic disease, and detection of malignancy in effusion samples frequently leads to a disease upstaging. Our purpose was to quantify the DNA in pleural effusion and serum in patients presenting pleural effusion in order to assess the potential prognostic impact.

The DNA level was determined by amplifying hRNase P in paired samples of serum and pleural fluid in 70 consecutive patients with cancer showing pleural effusion. A group of 30 patients without cancer was included. The correlation between serum and pleural DNA was calculated. Survival curves according to serum and pleural DNA were analyzed.

Median DNA concentrations were greater in patients with neoplasia than in patients without malignancy: 105 ng/mL versus 40 ng/mL (P = 0.001) in serum samples, respectively; 93 ng/mL versus 21 ng/mL (P = 0.001) in pleural fluids, respectively. A positive correlation between serum and pleural levels was confirmed (r = 0.3; P < 0.05). Median survival time for patients with serum DNA < or = 105 ng/mL was 11.03 months in contrast to only 3.63 months for patients with higher values (P = 0.036). Accordingly, median survival time for patients with pleural DNA < or = 93 ng/mL was 12.3 months versus only 4.63 months in case of higher levels (P = 0.027).

This study shows that there is a strong correlation between higher levels of free DNA in pleural fluid or serum and malignancy. Survival is worse for patients with higher DNA levels in serum and pleural fluid.