title: Variability of dynamic 18F-FDG-PET data in breast cancer xenografts.
abstract: BACKGROUND
  A murine breast cancer xenograft model was employed to evaluate inter- and intra-variability of various parameters derived from dynamic positron emission tomography with [18F]-fluorodeoxyglucose as tracer (FDG-PET).
  
  
  METHODS
  Seventeen female athymic nude foxn1/nu mice with bilaterally implanted triple-negative basal-like ductal carcinoma (MAS98.12) breast cancer xenografts underwent a dynamic PET scan over an hour after injection of approximately 10 MBq FDG. Inter-animal data were obtained from the entire animal cohort, while intra-animal data were from four mice receiving an additional scan after one or two days. Standardised uptake values (SUVmax, SUVmean and SUVmedian) were estimated for all tumours at different time points. Tumour uptake was analysed with a kinetic two-compartment model for estimation of pharmacokinetic parameters. The coefficient of variation (CV) was calculated for all PET-derived metrics.
  
  
  RESULTS
  The CVs for SUVmean and SUVmedian were typically 10-20% for the tumours, depending on the time post-injection and group (intra vs. inter). The CV for SUVmax was mostly higher. The variability in the pharmacokinetic parameters ranged from 23 to almost 150%.
  
  
  CONCLUSIONS
  SUVmean and SUVmedian show less variability than SUVmax. The pharmacokinetic tumour metrics again display much greater variability than the SUV-based metrics. However, it is generally not known which of these metrics that best represents cancer aggressiveness and their use may still depend on the research questions addressed.
authors.affiliation: a Department of Physics , University of Oslo , Oslo , Norway.
authors.forename: Kathinka E
authors.initials: KE
authors.lastname: Pitman
authors.affiliation: a Department of Physics , University of Oslo , Oslo , Norway.|b Department of Medical Physics , Oslo University Hospital , Oslo , Norway.
authors.forename: Espen
authors.initials: E
authors.lastname: Rusten
authors.affiliation: c Department of Tumour Biology , Oslo University Hospital , Oslo , Norway.
authors.forename: Alexandr
authors.initials: A
authors.lastname: Kristian
authors.affiliation: a Department of Physics , University of Oslo , Oslo , Norway.|b Department of Medical Physics , Oslo University Hospital , Oslo , Norway.
authors.forename: Eirik
authors.initials: E
authors.lastname: Malinen
mesh_terms: D000818:Animals; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D064593:Heterografts; D008325:Mammary Neoplasms, Experimental / Q000000981:diagnostic imaging*; D008819:Mice, Nude; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D064726:Triple Negative Breast Neoplasms / Q000000981:diagnostic imaging*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18