title: Dynamic magnetic resonance imaging of regional contrast access as an additional prognostic factor in pediatric osteosarcoma.
abstract: BACKGROUND
  The purpose of this article was to evaluate the utility of a pharmacokinetically modeled measure of regional contrast access, based on dynamic contrast-enhanced magnetic resonance imaging (MRI) studies after preoperative chemotherapy, as a predictor of disease free survival in osteosarcoma.
  
  
  METHODS
  The kinetic parameters of a two-compartment pharmacokinetic model of MRI contrast agent accumulation were analyzed in relation to disease free survival in 31 patients who received protocol-based therapy for nonmetastatic osteosarcoma of the extremities. The modeled exchange rate of contrast between the plasma and the tumor extravascular extracellular fluid space served as a measure of regional contrast access. The prognostic impact of both the clinically accepted standard of histologic evaluation of tumor necrosis and the regional contrast access were analyzed with tumor size as an influential factor.
  
  
  RESULTS
  Although the histologic grade of response was not a statistically significant prognostic factor in these patients (P = 0.884), regional contrast access after preoperative chemotherapy was significantly predictive of disease free survival (P = 0.035) in the Cox proportional hazards model. Lower regional access before surgery and smaller tumor size were associated with a better treatment outcome. Log-rank analyses of Kaplan-Meier curves indicated that the impact of regional access was most pronounced in patients with larger tumors (P = 0.052). Higher regional access at presentation also was associated significantly with greater decreases during therapy.
  
  
  CONCLUSIONS
  Dynamic MRI estimates of regional contrast access after preoperative chemotherapy, when combined with tumor size, holds promise for the early identification of patients at risk of recurrence. The availability of such response predictors could facilitate the development of risk-adapted treatment approaches.
authors: Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA. gene.reddick@stjude.org
authors: W E
authors: WE
authors: Reddick
authors: S
authors: S
authors: Wang
authors: X
authors: X
authors: Xiong
authors: J O
authors: JO
authors: Glass
authors: S
authors: S
authors: Wu
authors: S C
authors: SC
authors: Kaste
authors: C B
authors: CB
authors: Pratt
authors: W H
authors: WH
authors: Meyer
authors: B D
authors: BD
authors: Fletcher
mesh_terms: D000293:Adolescent; D000328:Adult; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media / Q000493:pharmacokinetics*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D012516:Osteosarcoma / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality / Q000628:therapy; D011379:Prognosis; D016016:Proportional Hazards Models; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media