title: Detection of mutant free circulating tumor DNA in the plasma of patients with gastrointestinal stromal tumor harboring activating mutations of CKIT or PDGFRA.
abstract: OBJECTIVE
  In gastrointestinal stromal tumor (GIST), there is no biomarker available that indicates success or failure of therapy. We hypothesized that tumor-specific v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (CKIT)- or platelet-derived growth factor receptor-α (PDGFRA)-mutant DNA fragments can be detected and quantified in plasma samples of patients with GIST.
  
  
  METHODS
  We prospectively collected 291 plasma samples from 38 subjects with GIST harboring activating mutations of CKIT or PDGFRA detected in tumor tissue, irrespective of current disease status or treatment. We used allele-specific ligation PCR to detect mutant free circulating DNA (fcDNA).
  
  
  RESULTS
  We were able to detect fcDNA harboring the tumor mutation in 15 of 38 patients. Patients with active disease displayed significantly higher amounts of mutant fcDNA compared with patients in complete remission (CR). The amount of mutant fcDNA correlated with disease course. We observed repeated positive test results or an increase of mutant fcDNA in five patients with progressive disease or relapse. A decline of tumor fcDNA or conversion from positive to negative was seen in five patients responding to treatment. A negative to positive conversion was seen in two patients with relapse and one patient with progression. In two cases, we aimed to identify additional mutations and found four additional exchanges, including mutations not known from sequentially conducted tumor biopsies.
  
  
  CONCLUSIONS
  Our results indicate that fcDNA harboring tumor-specific mutations in the plasma of patients with GIST can be used as tumor-specific biomarker. The detection of resistance mutations in plasma samples might allow earlier treatment changes and obviates the need for repeated tumor biopsies.
authors.affiliation: Center for Internal Medicine, Department of Hematology/Oncology and Hemostaseology, University of Leipzig, Leipzig, Germany.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Maier
authors.forename: Thoralf
authors.initials: T
authors.lastname: Lange
authors.forename: Irina
authors.initials: I
authors.lastname: Kerle
authors.forename: Katja
authors.initials: K
authors.lastname: Specht
authors.forename: Melanie
authors.initials: M
authors.lastname: Bruegel
authors.forename: Claudia
authors.initials: C
authors.lastname: Wickenhauser
authors.forename: Philipp
authors.initials: P
authors.lastname: Jost
authors.forename: Dietger
authors.initials: D
authors.lastname: Niederwieser
authors.forename: Christian
authors.initials: C
authors.lastname: Peschel
authors.forename: Justus
authors.initials: J
authors.lastname: Duyster
authors.forename: Nikolas
authors.initials: N
authors.lastname: von Bubnoff
mesh_terms: D000328:Adult; D000818:Animals; D014408:Biomarkers, Tumor / Q000097:blood*; D004247:DNA / Q000097:blood* / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000097:blood* / Q000235:genetics* / Q000473:pathology; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000473:pathology; D009360:Neoplastic Cells, Circulating; D011379:Prognosis; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; D004247:DNA; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha