title: Minimal residual disease (MRD) measurement as a tool to compare the efficacy of chemotherapeutic drug regimens using Escherichia Coli-asparaginase or Erwinia-asparaginase in childhood acute lymphoblastic leukemia (ALL).
abstract: BACKGROUND
  L-asparaginase is a crucial drug in childhood acute lymphoblastic leukemia (ALL) induction therapy, but much debate remains regarding the optimal formulation and dosage. As minimal residual disease (MRD) can accurately measure extremely low levels of lymphoblasts, it is a sensitive reflection of leukemia cell kill. We utilized MRD to compare the efficacy of Erwinia-asparaginase (Erwinia-asp) and E. coli-asparaginase (E. coli-asp) during induction therapy for childhood ALL.
  
  
  METHODS
  Of 116 precursor-B ALL patients, 22 were treated with Erwinia-asp, 90 with E. coli-asp, and 4 were switched from E. coli-asp to Erwinia-asp. MRD levels at the end of induction were analyzed for 90 patients (Erwinia-asp = 16; E. coli-asp = 74). Patients were stratified into MRD > or =10(-2), between 10(-2)-10(-4) and < or =10(-4). Toxicity information during induction was available for 110 patients.
  
  
  RESULTS
  MRD was the only significant prognosticator compared to conventional criteria. Patients treated with Erwinia-asp were 6.7 times more likely to have MRD levels > or =10(-2) (P = 0.031), reflecting slower lymphoblast clearance. While non-asparaginase related toxicities were similar in both groups, more E. coli-asp patients experienced severe asparaginase-related toxicity.
  
  
  CONCLUSIONS
  E. coli-asp is superior to Erwinia-asp in childhood ALL induction. Although E. coli-asp is more toxic, this is balanced by better response to therapy. Early response to treatment as measured by MRD is a direct reflection of leukemic cell kill and is a significant prognosticator of eventual outcome, making it a good surrogate marker to evaluate the efficacy of induction drugs in childhood ALL.
authors.affiliation: Division of Haematology/Oncology, Department of Paediatrics, National University of Singapore, Singapore, Singapore.
authors.forename: Cecilia Sze
authors.initials: CS
authors.lastname: Kwok
authors.forename: Shirley Kow
authors.initials: SK
authors.lastname: Kham
authors.forename: Hany
authors.initials: H
authors.lastname: Ariffin
authors.forename: Hai Peng
authors.initials: HP
authors.lastname: Lin
authors.forename: Thuan Chong
authors.initials: TC
authors.lastname: Quah
authors.forename: Allen Eng
authors.initials: AE
authors.lastname: Yeoh
mesh_terms: D000293:Adolescent; D001215:Asparaginase / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D018572:Disease-Free Survival; D004885:Erwinia / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D018365:Neoplasm, Residual / Q000175:diagnosis* / Q000188:drug therapy* / Q000235:genetics; D016133:Polymerase Chain Reaction; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis* / Q000188:drug therapy* / Q000235:genetics; D012307:Risk Factors; D012680:Sensitivity and Specificity; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D001215:Asparaginase