This study assessed the radiation dosimetry of 99mTc-labeled ethylene dicysteine (EC) C225 (EC-C225), a promising radioligand for functional tumor imaging.
Methods: Whole-body scanning was performed on 6 patients with head and neck squamous cell carcinoma up to 24 h after administration of 99mTc-EC-C225. Alternate patients who had been randomized to receive C225 in a phase III trial received 99mTc-EC-C225 before their 20-mg test dose or after their 400 mg/m2 loading dose of unlabeled C225 (patients 1/3/5 and 2/4/6, respectively). Radiation dosimetry was assessed using the MIRD method.
Results: The critical organ was the kidney, with an average radiation-absorbed dose for all 6 patients of 0.0274 mGy/MBq. The average total-body absorbed dose was 0.0022 mGy/MBq (0.243 cGy/1,110 MBq).
Conclusion: The new radiopharmaceutical 99mTc-EC-C225 appears to have reasonable dosimetric properties for a diagnostic nuclear medicine agent. Correlation of the imaging results with clinical findings is the next step.