title: Minimal residual disease in peripheral blood at day 15 identifies a subgroup of childhood B-cell precursor acute lymphoblastic leukemia with superior prognosis.
abstract: BACKGROUND
  Most minimal residual disease-directed treatment interventions in current treatment protocols for acute lymphoblastic leukemia are based on bone marrow testing, which is a consequence of previous studies showing the superiority of bone marrow over peripheral blood as an investigational material. Those studies typically did not explore the prognostic impact of peripheral blood involvement and lacked samples from very early time points of induction.
  
  
  METHODS
  In this study, we employed real-time quantitative polymerase chain reaction analysis to examine minimal residual disease in 398 pairs of blood and bone marrow follow-up samples taken from 95 children with B-cell precursor acute lymphoblastic leukemia treated with the ALL IC-BFM 2002 protocol.
  
  
  RESULTS
  We confirmed the previously published poor correlation between minimal residual disease in blood and marrow at early treatment time points, with levels in bone marrow being higher than in blood in most samples (median 7.9-fold, range 0.04-8,293-fold). A greater involvement of peripheral blood at diagnosis was associated with a higher white blood cell count at diagnosis (P=0.003) and with enlargement of the spleen (P=0.0004) and liver (P=0.05). At day 15, a level of minimal residual disease in blood lower than 10(-4) was associated with an excellent 5-year relapse-free survival in 78 investigated patients (100% versus 69 ± 7%; P=0.0003). Subgroups defined by the level of minimal residual disease in blood at day 15 (high-risk: ≥ 10(-2), intermediate-risk: <10(-2) and ≥ 10(-4), standard-risk: <10(-4)) partially correlated with bone marrow-based stratification described previously, but the risk groups did not match completely. No other time point analyses were predictive of outcome in peripheral blood, except for a weak association at day 8.
  
  
  CONCLUSIONS
  Minimal residual disease in peripheral blood at day 15 identified a large group of patients with an excellent prognosis and added prognostic information to the risk stratification based on minimal residual disease at day 33 and week 12.
authors: Department of Pediatric Hematology and Oncology, Charles University, Prague, Czech Republic.
authors: Jana
authors: J
authors: Volejnikova
authors: Ester
authors: E
authors: Mejstrikova
authors: Tatana
authors: T
authors: Valova
authors: Leona
authors: L
authors: Reznickova
authors: Ladislava
authors: L
authors: Hodonska
authors: Vladimir
authors: V
authors: Mihal
authors: Jaroslav
authors: J
authors: Sterba
authors: Yahia
authors: Y
authors: Jabali
authors: Daniela
authors: D
authors: Prochazkova
authors: Bohumir
authors: B
authors: Blazek
authors: Jiri
authors: J
authors: Hak
authors: Zdenka
authors: Z
authors: Cerna
authors: Ondrej
authors: O
authors: Hrusak
authors: Jan
authors: J
authors: Stary
authors: Jan
authors: J
authors: Trka
authors: Eva
authors: E
authors: Fronkova
mesh_terms: D000293:Adolescent; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage*; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008297:Male; D018365:Neoplasm, Residual; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood* / Q000175:diagnosis* / Q000188:drug therapy* / Q000473:pathology; D011379:Prognosis; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors