Purpose: The aim of the study was to evaluate the inter- and intrapatient variability of positron emission tomography (PET) measurements of perfusion in advanced solid cancers.
Experimental design: Thirty-seven patients with predominantly intra-abdominal tumors underwent PET imaging using inhaled C15O2. Repeat data were obtained by scanning five patients twice, 1 week apart, with no intervening therapy. Regional flow and the volume of distribution (V(d)) were measured from dynamic images by use of a one-compartment model. Inter- and intrapatient variability were measured as the coefficient of variability (CV). Data were also obtained for regions of interest in normal liver, spleen, and kidney.
Results: The mean (+/-SD) regional flow in the tumors was 0.46 +/- 0.19 ml(blood)/min/ml(tissue), and the mean V(d) was 0.74 +/- 0.15 ml(blood)/ml(tissue). Variability in tumor flow was greater between (n = 37; CV = 41%) than within (n = 5; CV = 11%) patients. Variability in tumor V(d) was greater between (CV = 21%) than within (CV = 6%) patients. There was a good correlation between the repeat tumor data for both regional flow (rho = 0.82; P = 0.023) and V(d) (rho = 0.89; P = 0.007). Normal tissue variability was also greater between than within patients. In all cases, no statistically significant differences were seen between repeat measurements in the same patient.
Conclusions: Dynamic C15O2 PET measurements of regional flow are reproducible in patients with predominantly intra-abdominal malignancies and may be useful for the pharmacodynamic evaluation of novel antivascular and antiangiogenic cancer therapeutic agents.