Evaluation of Cu-PTSM as a tracer of tumor perfusion: comparison with labeled microspheres in spontaneous canine neoplasms.

Copper-62-labeled Cu-PTSM is a promising generator-produced PET tracer for myocardial, cerebral and renal perfusion. To evaluate whether [62Cu]Cu-PTSM could also serve as a blood flow tracer in PET studies of tumor tissue, the tumor uptake of [62Cu]Cu-PTSM was examined in dogs with spontaneously-occurring soft-tissue neoplasms. Copper-67-labeled Cu-PTSM was administered intravenously to four anesthetized dogs, followed c. 5 min later by a left ventricular injection of 85Sr-labeled microspheres (15 microns) to provide an independent measure of tumor perfusion. Forty-seven tumors (average weight = 2.5 +/- 3.7 g) were obtained and sectioned into 80 samples. The correlation of 67Cu-PTSM uptake with regional renal perfusion was also examined in data from 395 tissue samples ranging in flow from 0.02 to 9.39 mL min-1 g-1. Rates of tumor perfusion assessed with 85Sr-labeled microspheres ranged from 0.011 to 3.0 mL min-1 g-1. No correlation was found between tumor size and the rate of tumor perfusion. However, an excellent linear correlation exists between tumor perfusion calculated from [62Cu]Cu-PTSM data and tumor perfusion measured with 85Sr-microspheres (r = 0.94 for 80 samples), suggesting that [62Cu]Cu-PTSM may be useful as a radiopharmaceutical for PET studies of tumor perfusion.