Cell-free DNA concentration in pleural fluid and serum:: Quantitative approach and potential prognostic factor in patients with cancer and pleural effusions

PURPOSE: 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. PATIENTS AND METHODS: 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. RESULTS: 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 :5 105 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 f-. 93 ng/mL was 12.3 months versus only 4.63 months in case of higher levels (P = 0.027). CONCLUSION: 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.