title: Circulating Plasma Tumor DNA.
abstract: Circulating cell-free DNA (ccfDNA)--first identified in 1947--is "naked" DNA that is free-floating in the blood, and derived from both normal and diseased cells. In the 1970s, scientists observed that patients with cancer had elevated levels of ccfDNA as compared to their healthy, cancer-free counterparts. The maternal fetal medicine community first developed techniques to identify the small fraction of fetal-derived ccfDNA for diagnostic purposes. Similarly, due to the presence of tumor-specific (somatic) variations in all cancers, the fraction of circulating cell-free plasma tumor DNA (ptDNA) in the larger pool of ccfDNA derived from normal cells can serve as extremely specific blood-based biomarkers for a patient's cancer. In theory this "liquid biopsy" can provide a real-time assessment of molecular tumor genotype (qualitative) and existing tumor burden (quantitative). Historically, the major limitation for ptDNA as a biomarker has been related to a low detection rate; however, current and developing techniques have improved sensitivity dramatically. In this chapter, we discuss these methods, including digital polymerase chain reaction and various approaches to tagged next-generation sequencing.
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Bunting and Blaustein Building, 1650 Orleans Street, Room 151, 21287, Baltimore, MD, USA.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Parsons
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Bunting and Blaustein Building, 1650 Orleans Street, Room 151, 21287, Baltimore, MD, USA.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Beaver
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins School of Medicine, Bunting and Blaustein Building, 1650 Orleans Street, Room 151, 21287, Baltimore, MD, USA. bpark2@jhmi.edu.
authors.forename: Ben H
authors.initials: BH
authors.lastname: Park
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics; D001943:Breast Neoplasms / Q000097:blood* / Q000235:genetics / Q000473:pathology / Q000628:therapy; D004273:DNA, Neoplasm / Q000097:blood* / Q000235:genetics; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011379:Prognosis
chemical_list: D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm
keywords: Breast cancer biomarker; Cancer biomarker; Circulating cell-free DNA; Digital PCR; Plasma tumor DNA; Tagged next-generation sequencing