title: Quantification of free circulating tumor DNA as a diagnostic marker for breast cancer.
abstract: OBJECTIVE
  To determine whether the amounts of circulating DNA could discriminate between breast cancer patients and healthy individuals by using real-time PCR quantification methodology.
  
  
  METHODS
  Our standard protocol for quantification of cell-free plasma DNA involved 175 consecutive patients with breast cancer and 80 healthy controls.
  
  
  RESULTS
  We found increased levels of circulating DNA in breast cancer patients compared to control individuals (105.2 vs. 77.06 ng/mL, p < 0.001). We also found statistically significant differences in circulating DNA amounts in patients before and after breast surgery (105.2 vs. 59.0 ng/mL, p = 0.001). Increased plasma cell-free DNA concentration was a strong risk factor for breast cancer, conferring an increased risk for the presence of this disease (OR, 12.32; 95% CI, 2.09-52.28; p < 0.001).
  
  
  CONCLUSIONS
  Quantification of circulating DNA by real-time PCR may be a good and simple tool for detection of breast cancer with a potential to clinical applicability together with other current methods used for monitoring the disease.
authors.affiliation: Molecular Oncology Group and Virology Laboratory, Portuguese Institute of Oncology, Porto, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Catarino
authors.forename: Maria M
authors.initials: MM
authors.lastname: Ferreira
authors.forename: Helena
authors.initials: H
authors.lastname: Rodrigues
authors.forename: Ana
authors.initials: A
authors.lastname: Coelho
authors.forename: Ana
authors.initials: A
authors.lastname: Nogal
authors.forename: Abreu
authors.initials: A
authors.lastname: Sousa
authors.forename: Rui
authors.initials: R
authors.lastname: Medeiros
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood* / Q000175:diagnosis*; D004247:DNA / Q000097:blood* / Q000235:genetics; D004273:DNA, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011174:Portugal; D011237:Predictive Value of Tests; D012016:Reference Values; D012307:Risk Factors
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D004247:DNA