title: Effects of prolonged storage of whole plasma or isolated plasma DNA on the results of circulating DNA quantification assays.
abstract: Analysis of molecular markers in biological fluids has been proposed as a tool for early detection and monitoring of cancer. Circulating plasma DNA concentrations have been found to be higher in cancer patients than in cancer-free control subjects, but little is known about the effect of specimen storage on plasma DNA concentrations. Here we investigated the impact of long-term storage of both plasma samples and purified plasma DNA on the reproducibility of plasma DNA quantification as determined using real-time polymerase chain reaction analysis. The analysis was performed on samples from a subset of 34 lung cancer patients and 28 matched control subjects selected from 200 subjects in our previously published case-control study and from 117 cancer-free smokers enrolled in a lung cancer screening program. Two samples of plasma and isolated DNA were assessed for each patient, with a median of 41 months between the first and second assessments for participants in the case-control study and 9 months for participants in the screening study. DNA levels declined substantially between the two assessments at an average rate of approximately 30% per year. These data provide valuable information for the rational planning of retrospective studies of banked series of biological samples, particularly if collected over a long period of time, as can occur in large clinical trials.
authors.affiliation: Department of Experimental Oncology, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy. gabriella.sozzi@istitutotumori.mi.it
authors.forename: Gabriella
authors.initials: G
authors.lastname: Sozzi
authors.forename: Luca
authors.initials: L
authors.lastname: Roz
authors.forename: Davide
authors.initials: D
authors.lastname: Conte
authors.forename: Luigi
authors.initials: L
authors.lastname: Mariani
authors.forename: Francesca
authors.initials: F
authors.lastname: Andriani
authors.forename: Paolo
authors.initials: P
authors.lastname: Verderio
authors.forename: Ugo
authors.initials: U
authors.lastname: Pastorino
mesh_terms: D014408:Biomarkers, Tumor / Q000097:blood*; D001793:Blood Preservation; D016022:Case-Control Studies; D004273:DNA, Neoplasm / Q000097:blood*; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm