Quantification of CCI-103F labeling heterogeneity in canine solid tumors

Int J Radiat Oncol Biol Phys. 1997 Feb 1;37(3):655-62. doi: 10.1016/s0360-3016(96)00559-7.


Purpose: 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 and materials: 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.

Conclusion: Despite intratumor variation, acceptable estimates of nitroimidazole-labeled cells in a tumor may be obtained from a clinically feasible number of biopsies.

MeSH terms

  • Analysis of Variance
  • Animals
  • Biomarkers
  • Cell Hypoxia*
  • Dog Diseases* / pathology
  • Dogs
  • Neoplasms / pathology
  • Neoplasms / veterinary*
  • Nitroimidazoles*
  • Oxygen / analysis
  • Reproducibility of Results


  • Biomarkers
  • Nitroimidazoles
  • CCI 103F
  • Oxygen