title: Quantitative analysis of circulating plasma DNA as a tumor marker in thoracic malignancies.
abstract: BACKGROUND
  Increased plasma DNA has been found in cancer patients and may have potential as a tumor marker. The objectives of this study were to develop a controlled, quantitative PCR (QPCR) assay to measure plasma DNA and then evaluate plasma DNA concentrations as a tumor marker in patients with thoracic malignancies.
  
  
  METHODS
  We developed a QPCR assay for DNA, using the human beta-actin gene. Plasma samples were analyzed from 58 patients with esophageal cancer (EC; 20 banked samples and 38 prospectively collected samples) and 25 patients with lung cancer (LC; all prospectively collected). Control groups consisting of 51 patients with gastroesophageal reflux disease (GERD; 23 banked samples and 28 prospectively collected) and 11 healthy volunteers were also analyzed.
  
  
  RESULTS
  The assay had an experimental variability <4%. In our banked samples, the mean concentration of plasma DNA in EC was 819.0 microg/L (range, 46.2-4738.0 microg/L) vs 432.0 microg/L (6.0-2888.0 microg/L) in GERD (P = 0.02). However, the prospectively collected samples had lower DNA concentrations, and there was no difference between cancer patients and controls. The mean DNA concentration was 10.6 microg/L (range, 7.0-14.0 microg/L) in healthy volunteers and 10.5 microg/L (range, 4.0-23.5 microg/L) in GERD controls vs 13.0 microg/L (range, 4.5-46.5 microg/L) in EC and 14.6 microg/L (range, 3.0-30.0 microg/L) in LC.
  
  
  CONCLUSIONS
  Our data indicate that plasma DNA concentrations are of limited diagnostic value when samples are prospectively collected and uniformly handled. This is in contrast to previously published results. Qualitative analysis of DNA may be needed if plasma nucleic acids are to be used as a diagnostic tool in cancer screening.
authors.affiliation: Department of Surgery, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Luis J
authors.initials: LJ
authors.lastname: Herrera
authors.forename: Siva
authors.initials: S
authors.lastname: Raja
authors.forename: William E
authors.initials: WE
authors.lastname: Gooding
authors.forename: Talal
authors.initials: T
authors.lastname: El-Hefnawy
authors.forename: Lori
authors.initials: L
authors.lastname: Kelly
authors.forename: James D
authors.initials: JD
authors.lastname: Luketich
authors.forename: Tony E
authors.initials: TE
authors.lastname: Godfrey
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D004273:DNA, Neoplasm / Q000097:blood*; D004938:Esophageal Neoplasms / Q000175:diagnosis; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis; D010949:Plasma; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D015203:Reproducibility of Results; D013899:Thoracic Neoplasms / Q000175:diagnosis*
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm