title: Comparative analysis of different approaches to measure treatment response in acute myeloid leukemia.
abstract: OBJECTIVE
  In acute myeloid leukemia (AML), initial treatment response by morphologic analysis of bone marrow predicts long-term outcome. Response can now be assessed by minimal residual disease (MRD) monitoring with flow cytometry or polymerase chain reaction (PCR). We determined the relation among the results of these approaches and their prognostic value.
  
  
  METHODS
  In the multicenter AML02 study, follow-up bone marrow samples from 203 children and adolescents with newly diagnosed AML were examined by flow cytometry (n = 1,514), morphology (n = 1,382), and PCR amplification of fusion transcripts (n = 508). Results were correlated with treatment outcome.
  
  
  RESULTS
  Among 1,215 samples with less than 5% leukemic myeloblasts by morphology, 100 (8.2%) were MRD positive (≥ 0.1%) by flow cytometry, whereas 96 (57.5%) of the 167 samples with ≥ 5% blasts were MRD negative. Virtually all (308 of 311; 99.0%) MRD-negative samples by PCR were also MRD negative by flow cytometry. However, only 19 (9.6%) of the 197 PCR-positive samples were flow cytometry positive, with analyses of AML1-ETO and CBFβ-MYH11 accounting for most discrepancies, whereas eight of 13 MLL-positive samples had detectable MRD by flow cytometry. MRD by flow cytometry after induction 1 or 2 predicted lower event-free survival and higher relapse rate (P < .001) and was an independent prognostic factor in a multivariable analysis; prediction was not improved by morphologic information or molecular findings.
  
  
  CONCLUSIONS
  In childhood AML, morphologic assessment of treatment response has limited value if MRD is measured by flow cytometry. MLL fusion transcripts can provide prognostic information in some patients, whereas monitoring of AML1-ETO and CBFβ-MYH11 transcripts is largely uninformative.
authors.affiliation: Department of Oncology, MS 260, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA. hiroto.inaba@stjude.org
authors.forename: Hiroto
authors.initials: H
authors.lastname: Inaba
authors.forename: Elaine
authors.initials: E
authors.lastname: Coustan-Smith
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Cao
authors.forename: Stanley B
authors.initials: SB
authors.lastname: Pounds
authors.forename: Sheila A
authors.initials: SA
authors.lastname: Shurtleff
authors.forename: Kathleen Y
authors.initials: KY
authors.lastname: Wang
authors.forename: Susana C
authors.initials: SC
authors.lastname: Raimondi
authors.forename: Mihaela
authors.initials: M
authors.lastname: Onciu
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Jacobsen
authors.forename: Raul C
authors.initials: RC
authors.lastname: Ribeiro
authors.forename: Gary V
authors.initials: GV
authors.lastname: Dahl
authors.forename: W Paul
authors.initials: WP
authors.lastname: Bowman
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Taub
authors.forename: Barbara
authors.initials: B
authors.lastname: Degar
authors.forename: Wing
authors.initials: W
authors.lastname: Leung
authors.forename: James R
authors.initials: JR
authors.lastname: Downing
authors.forename: Ching-Hon
authors.initials: CH
authors.lastname: Pui
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Rubnitz
authors.forename: Dario
authors.initials: D
authors.lastname: Campana
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000704:Analysis of Variance; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001853:Bone Marrow / Q000473:pathology*; D002648:Child; D015331:Cohort Studies; D018572:Disease-Free Survival; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry; D053208:Kaplan-Meier Estimate; D015470:Leukemia, Myeloid, Acute / Q000175:diagnosis* / Q000188:drug therapy / Q000401:mortality*; D008297:Male; D009010:Monte Carlo Method; D018365:Neoplasm, Residual / Q000175:diagnosis* / Q000188:drug therapy / Q000401:mortality*; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012737:Sex Factors; D016019:Survival Analysis