title: Quantitative monitoring of NPM1 mutations provides a valid minimal residual disease parameter following allogeneic stem cell transplantation.
abstract: BACKGROUND
  Minimal residual disease (MRD) diagnostics in acute myeloid leukemia (AML) gain increasing importance after allogeneic stem cell transplantation (SCT). Nucleophosmin (NPM1) mutations, with their high frequency in AML, were suggested to represent suitable MRD markers, but so far no study has evaluated their usefulness in the posttransplantation period.
  
  
  METHODS
  We evaluated the validity of this MRD marker in the posttransplantation period in a cohort of 13 patients with an NPM1A mutation (NPM1Amut). For this most frequent NPM1A subtype, quantitative real-time polymerase chain reaction (qPCR) was retrospectively performed on bone marrow/peripheral blood samples that had been taken before and after SCT.
  
  
  RESULTS
  NPM1Amut was retrospectively followed up in 13 patients who received 14 transplantations. One-hundred and thirty-nine qPCR analyses were performed (median: 7 time points; median follow-up: 216 days; range, 35-1825 days). After SCT, 10 of 14 NPM1Amut cases (71%) became PCR-negative, of which four achieved stable remissions. All four patients (29%) who remained NPM1Amut-positive after SCT relapsed. In all nine relapse cases, increases of NPM1Amut were seen that preceded morphological relapse and the decrease of molecular chimerism with mean intervals of 24 days (range, 12-38 days) and 15 days (range, 1-36 days), respectively.
  
  
  CONCLUSIONS
  Quantitative assessment of NPM1Amut seems to provide a reliable MRD marker in the posttransplantation period, predicting relapse earlier than morphology or molecular chimerism, which should be confirmed in larger studies.
authors.affiliation: Clinic for Stem Cell Transplantation, University of Hamburg, Germany. u.bacher@uke.de
authors.forename: Ulrike
authors.initials: U
authors.lastname: Bacher
authors.forename: Anita
authors.initials: A
authors.lastname: Badbaran
authors.forename: Boris
authors.initials: B
authors.lastname: Fehse
authors.forename: Tatjana
authors.initials: T
authors.lastname: Zabelina
authors.forename: Axel Rolf
authors.initials: AR
authors.lastname: Zander
authors.forename: Nicolaus
authors.initials: N
authors.lastname: Kröger
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000378:metabolism / Q000628:therapy; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009154:Mutation; D018365:Neoplasm, Residual; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D000090243:Nucleophosmin; D012008:Recurrence; D012074:Remission Induction; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D033581:Stem Cell Transplantation; D013997:Time Factors; D018183:Transplantation Chimera / Q000235:genetics* / Q000378:metabolism; D014184:Transplantation, Homologous
chemical_list: D014408:Biomarkers, Tumor; C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D000090243:Nucleophosmin