title: Using pharmacokinetic and pharmacodynamic modeling and simulation to evaluate importance of schedule in topotecan therapy for pediatric neuroblastoma.
abstract: OBJECTIVE
  The study aims to use mathematical modeling and simulation to assess the relative contribution of topotecan systemic exposure and scheduling in the activity and myelosuppression of topotecan in pediatric patients with neuroblastoma.
  
  
  METHODS
  Pharmacokinetic and pharmacodynamic data were obtained from a phase II study for pediatric patients with high-risk neuroblastoma. The topotecan dosage was individualized to attain a topotecan lactone area under the plasma concentration-time curve between 80 and 120 ng/mL h and given over a protracted schedule (i.e., 10 days). Four mathematical models describing topotecan pharmacokinetics, tumor growth, and neutrophil and platelet dynamics were developed. The models were combined to simulate and compare different topotecan treatment strategies with respect to systemic exposure and schedule.
  
  
  RESULTS
  The median change in tumor volume was significantly different between schedules (5% increase for D x 5 versus 60% decrease for D x 5 x 2; P < 0.0001) when administering the same total systemic exposure. Whereas protracted schedules showed increased neutropenia (median of 7 versus 12 days below an absolute neutrophil count of 500/microL; P < 0.0001) and thrombocytopenia (median of 3 versus 10 days below a platelet count of 20,000/microL; P < 0.00001), simulations showed that delays in topotecan therapy would not be required. Simulations showed that an increase in topotecan exposure on the D x 5 schedule by 2.4-fold resulted in a modest decrease in tumor volume (i.e., median percentage change tumor volume of 24% versus 3%).
  
  
  CONCLUSIONS
  The present mathematical model gave an innovative approach to determining relevant topotecan schedules for possible evaluation in the clinic, which could lead to improved tumor response with minimized toxicities.
authors.affiliation: Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Panetta
authors.forename: Paula
authors.initials: P
authors.lastname: Schaiquevich
authors.forename: Victor M
authors.initials: VM
authors.lastname: Santana
authors.forename: Clinton F
authors.initials: CF
authors.lastname: Stewart
mesh_terms: D000293:Adolescent; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002648:Child; D002675:Child, Preschool; D017322:Clinical Trials, Phase II as Topic; D004334:Drug Administration Schedule; D049690:History, Ancient; D006801:Humans; D007231:Infant, Newborn; D008962:Models, Theoretical; D009447:Neuroblastoma / Q000188:drug therapy*; D019772:Topotecan / Q000008:administration & dosage* / Q000493:pharmacokinetics*
chemical_list: D000970:Antineoplastic Agents; D019772:Topotecan