title: Tumor size as a predictor of outcome in pediatric non-metastatic osteosarcoma of the extremity.
abstract: BACKGROUND
  Better predictors of outcome would allow improved risk-adapted therapy for pediatric nonmetastatic osteosarcoma of the extremity. We investigated the predictive value of MR imaging-based measures of absolute and relative tumor size and volume at the time of diagnosis. We also assessed the relation of tumor size to age and histologic response.
  
  
  METHODS
  We retrospectively abstracted demographic, treatment history, and outcome information of patients treated on a single institutional protocol. A single pediatric oncologic radiologist manually measured each primary lesion and the affected native bone in three dimensions on MR images obtained at the time of diagnosis. Eight parameters of tumor size were analyzed for their value in predicting overall survival (OS) and event-free survival (EFS).
  
  
  RESULTS
  The median age of the 42 patients was 13.5 years (range: 5.9-18.7 years); 50% were female and 74% were Caucasian. Absolute tumor volume was an important predictor of OS (P < 0.05); absolute tumor depth (analyzed as a continuous variable) was a significant predictor of OS (P = 0.018) and EFS (P = 0.036). Relative measures of tumor size were not found to predict outcome. No relation was seen between tumor size and histologic response.
  
  
  CONCLUSIONS
  Absolute tumor size at the time of diagnosis is significantly predictive of OS and EFS. If validated in a larger study, this indicator should be used in the design of risk-adapted treatment protocols for osteosarcoma.
authors.affiliation: Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA. sue.kaste@stjude.org
authors.forename: Sue C
authors.initials: SC
authors.lastname: Kaste
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.forename: C A
authors.initials: CA
authors.lastname: Billups
authors.forename: N C
authors.initials: NC
authors.lastname: Daw
authors.forename: C B
authors.initials: CB
authors.lastname: Pratt
authors.forename: W H
authors.initials: WH
authors.lastname: Meyer
mesh_terms: D000293:Adolescent; D002648:Child; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D012516:Osteosarcoma / Q000175:diagnosis* / Q000401:mortality; D011379:Prognosis; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome; D047368:Tumor Burden