Abstract
2234
Objectives: Initial patient therapy studies with I-131 Chlorotoxin (Transmolecular Inc) have been performed utilizing intracavitary injections. Recent investigations have utilized intravenous administrations of I-131 Chlorotoxin therapy. The purpose of the study was to perform pharmacokinetic analysis and image localization studies with intravenous I-131 Chlorotoxin in patients with primary malignant glioma or cerebral metastatic solid tumors.
Methods: Six patients received from 1 to 3 treatment doses intravenously (10 to 30 mCi/dose) of I-131 Chlorotoxin. Multiple whole body images were obtained at 1 hour and up to 72 hours after radiopharmaceutical injection (5 images). Blood samples were obtained following each whole body image and urine was collected for the first 24 hours post injection. Blood and urine activity was counted and blood activity clearance was determined. The blood pool and total urine activity at 24 hours was calculated and expressed as a percent of injected dose (ID). Patient images were evaluated for tumor specific uptake.
Results: Evaluation of blood pool activity demonstrated a biexponential clearance with an initial and delayed T1/2b of 7.6 hrs ± 2.6 hrs (SD n=10) and 83.0 hrs ± 14.9 hrs (SD n=11), respectively. Blood pool and urine activity levels at 24 hours were 4.5% ID ± 0.02% ID and 49.7% ID ± 0.1% ID, respectively, indicating rapid blood pool clearance and rapid urinary accumulation of I-131 Chlorotoxin. Of the 6 patients, 1 patient’s study was incomplete and tumor specific uptake was observed in 3 of the remaining 5 patients.
Conclusions: Imaging and pharmacokinetic analysis of I-131 Chlorotoxin was performed. Rapid blood clearance and urine accumulation of I-131 Chlorotoxin was noted. Tumor specific uptake was observed in 3 of 6 patients.
- Society of Nuclear Medicine, Inc.