title: Quantification of CCI-103F labeling heterogeneity in canine solid tumors.
abstract: OBJECTIVE
  The purposes of this study were to assess sources of variation in the distribution of nitroimidazole-labeled hypoxic cells in canine tumors and to quantify the reliability of estimating overall nitroimidazole-labeled area fraction from biopsies.
  
  
  METHODS
  Hypoxic cells were labeled in 24 canine tumors by immunostaining of the nitroimidazole hypoxia marker CCI-103F. In tumors with a volume < 100 cm3, each cubic centimeter of tumor was examined; in larger tumors 100 randomly selected 1 cm3 samples were examined. These data were used to estimate the overall CCI-103F-labeled area fraction in the tumor. A variance components model was used to quantify intertumoral, intratumoral, and within slide (residual) sources of variation. The ability to estimate intratumoral CCI-103F-labeled area fraction based on information obtained from biopsies was assessed by randomly selecting two or four samples from the dataset for each tumor and comparing the mean CCI-103F-labeled area fraction from this limited sample to the labeled area fraction based on each cubic centimeter; this simulation process was repeated 1000 times.
  
  
  RESULTS
  Intratumoral (27% of total) and intertumoral (30% of total) variation in CCI-103F-labeled area fraction were similar. Residual variation (variation at the microscopic level) accounted for 43% of total variation in CCI-103F labeling. Intratumoral variation in labeling decreased as the intratumoral CCI-103F mean labeled area fraction decreased. The accuracy of estimating the intratumoral CCI-103F-labeled area fraction in a tumor from limited sampling increased as the number of samples increased or the intratumoral labeled area fraction decreased. When four random samples were used to estimate overall CCI-103F-labeled area fraction in the tumor, estimates from approximately 90% of the 1000 simulations were within 0.10 of the intratumoral CCI-103F-labeled area fraction. Classifying a minimally labeled tumor as unlabeled based on limited sampling was unlikely.
  
  
  CONCLUSIONS
  Despite intratumor variation, acceptable estimates of nitroimidazole-labeled cells in a tumor may be obtained from a clinically feasible number of biopsies.
authors.affiliation: North Carolina State University, College of Veterinary Medicine, Raleigh 27608, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Cline
authors.forename: G L
authors.initials: GL
authors.lastname: Rosner
authors.forename: J A
authors.initials: JA
authors.lastname: Raleigh
authors.forename: D E
authors.initials: DE
authors.lastname: Thrall
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers; D015687:Cell Hypoxia; D004283:Dog Diseases / Q000473:pathology; D004285:Dogs; D009369:Neoplasms / Q000473:pathology / Q000662:veterinary*; D009593:Nitroimidazoles; D010100:Oxygen / Q000032:analysis; D015203:Reproducibility of Results; D005466:Fluorocarbons
chemical_list: D015415:Biomarkers; D009593:Nitroimidazoles; D010100:Oxygen; C049948:CCI 103F; D005466:Fluorocarbons