title: Poor drug distribution as a possible explanation for the results of the PRECISE trial.
abstract: OBJECTIVE
  Convection-enhanced delivery (CED) is a novel intracerebral drug delivery technique with considerable promise for delivering therapeutic agents throughout the CNS. Despite this promise, Phase III clinical trials employing CED have failed to meet clinical end points. Although this may be due to inactive agents or a failure to rigorously validate drug targets, the authors have previously demonstrated that catheter positioning plays a major role in drug distribution using this technique. The purpose of the present work was to retrospectively analyze the expected drug distribution based on catheter positioning data available from the CED arm of the PRECISE trial.
  
  
  METHODS
  Data on catheter positioning from all patients randomized to the CED arm of the PRECISE trial were available for analyses. BrainLAB iPlan Flow software was used to estimate the expected drug distribution.
  
  
  RESULTS
  Only 49.8% of catheters met all positioning criteria. Still, catheter positioning score (hazard ratio 0.93, p = 0.043) and the number of optimally positioned catheters (hazard ratio 0.72, p = 0.038) had a significant effect on progression-free survival. Estimated coverage of relevant target volumes was low, however, with only 20.1% of the 2-cm penumbra surrounding the resection cavity covered on average. Although tumor location and resection cavity volume had no effect on coverage volume, estimations of drug delivery to relevant target volumes did correlate well with catheter score (p < 0.003), and optimally positioned catheters had larger coverage volumes (p < 0.002). Only overall survival (p = 0.006) was higher for investigators considered experienced after adjusting for patient age and Karnofsky Performance Scale score.
  
  
  CONCLUSIONS
  The potential efficacy of drugs delivered by CED may be severely constrained by ineffective delivery in many patients. Routine use of software algorithms and alternative catheter designs and infusion parameters may improve the efficacy of drugs delivered by CED.
authors.affiliation: Division of Neurosurgery, Department of Surgery, Duke University, Durham, North Carolina, USA. john.sampson@duke.edu
authors.forename: John H
authors.initials: JH
authors.lastname: Sampson
authors.forename: Gary
authors.initials: G
authors.lastname: Archer
authors.forename: Christoph
authors.initials: C
authors.lastname: Pedain
authors.forename: Eva
authors.initials: E
authors.lastname: Wembacher-Schröder
authors.forename: Manfred
authors.initials: M
authors.lastname: Westphal
authors.forename: Sandeep
authors.initials: S
authors.lastname: Kunwar
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vogelbaum
authors.forename: April
authors.initials: A
authors.lastname: Coan
authors.forename: James E
authors.initials: JE
authors.lastname: Herndon
authors.forename: Raghu
authors.initials: R
authors.lastname: Raghavan
authors.forename: Martin L
authors.initials: ML
authors.lastname: Brady
authors.forename: David A
authors.initials: DA
authors.lastname: Reardon
authors.forename: Allan H
authors.initials: AH
authors.lastname: Friedman
authors.forename: Henry S
authors.initials: HS
authors.lastname: Friedman
authors.forename: M Inmaculada
authors.initials: MI
authors.lastname: Rodríguez-Ponce
authors.forename: Susan M
authors.initials: SM
authors.lastname: Chang
authors.forename: Stephan
authors.initials: S
authors.lastname: Mittermeyer
authors.forename: David
authors.initials: D
authors.lastname: Croteau
authors.forename: Raj K
authors.initials: RK
authors.lastname: Puri
mesh_terms: D000465:Algorithms; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001932:Brain Neoplasms / Q000188:drug therapy*; D002404:Catheterization / Q000379:methods* / Q000706:statistics & numerical data; D017326:Clinical Trials, Phase III as Topic / Q000379:methods; D018481:Convection; D016503:Drug Delivery Systems / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D018793:Interleukin-13; D053208:Kaplan-Meier Estimate; D016016:Proportional Hazards Models; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012189:Retrospective Studies; D012984:Software; D014018:Tissue Distribution; D017211:Treatment Failure
chemical_list: D000970:Antineoplastic Agents; D018793:Interleukin-13