title: Pretreatment plasma folate modulates the pharmacodynamic effect of high-dose methotrexate in children with acute lymphoblastic leukemia and non-Hodgkin lymphoma: "folate overrescue" concept revisited.
abstract: BACKGROUND
  To evaluate the influence of pretreatment plasma folate concentrations on methotrexate exposure in children with acute lymphoblastic leukemia/non-Hodgkin lymphoma treated with high-dose methotrexate, we assessed time profiles of plasma homocysteine, folate, and vitamin B(12) concentrations in children treated with high-dose methotrexate with leucovorin rescue.
  
  
  METHODS
  We analyzed 98 treatment courses. The study endpoints were to determine how methotrexate exposure is related to homocysteine accumulation and whether it is influenced by pretreatment plasma folate.
  
  
  RESULTS
  Peak concentrations of homocysteine increased from the start of the intravenous infusion through cessation of methotrexate therapy up to time point t(42), when this trend was reversed by administration of folinic acid. The area under the curve (AUC) for plasma homocysteine showed decreasing course-to-course tendencies with a statistically significant decrease only between courses 1 and 2 (P <or=0.05), indicating decreased whole-body homocysteine accumulation in response to administration of consecutive methotrexate courses. Therapeutic courses with low initial folate concentrations (<or=10 nmol/L) gave significantly higher responses in homocysteine accumulation expressed both as (hcys)AUC(0-66 h) and the peak t(42) homocysteine concentrations than did courses with initial folate >10 nmol/L. Correspondingly, in the courses with low initial folate, peak plasma concentrations of methotrexate were significantly higher than in courses with high precourse concentrations of plasma folate.
  
  
  CONCLUSIONS
  Endogenous pretreatment plasma folate modulates the magnitude of the methotrexate effect, providing support for a "folate overrescue" concept.
authors.affiliation: Department of Pediatric Oncology, University Hospital, Brno, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Sterba
authors.forename: Ladislav
authors.initials: L
authors.lastname: Dusek
authors.forename: Regina
authors.initials: R
authors.lastname: Demlova
authors.forename: Dalibor
authors.initials: D
authors.lastname: Valik
mesh_terms: D000293:Adolescent; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006710:Homocysteine / Q000097:blood; D006801:Humans; D007223:Infant; D002955:Leucovorin / Q000627:therapeutic use*; D008228:Lymphoma, Non-Hodgkin / Q000097:blood / Q000188:drug therapy*; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood / Q000188:drug therapy*; D014805:Vitamin B 12 / Q000097:blood; D014803:Vitamin B Complex / Q000627:therapeutic use*
chemical_list: D000964:Antimetabolites, Antineoplastic; D006710:Homocysteine; D014803:Vitamin B Complex; D005492:Folic Acid; D014805:Vitamin B 12; D002955:Leucovorin; D008727:Methotrexate