IMAGING PROSTATE-CANCER WITH TECHNETIUM-99M-7E11-C5.3 (CYT-351)

To evaluate the performance of the Tc-99m-labeled monoclonal antibody CYT-351 in visualizing prostate cancer, radioimmunoscintigraphy (RIS) was performed in 35 patients. Methods: Antibody (0.5 mg) labeled with 600 MBq Tc-99m was injected intravenously after obtaining informed con sent. Planar and SPECT imaging was performed at 10 min and 6-8 and 22- 24 hr postinjection. The scans were evaluated for visualization of the primary focus or local recurrence, extraprostatic invasion, lymph nod e involvement and uptake in bone and soft tissue metastases. Results: Thirty-six studies in 35 patients were performed. In 13/14 evaluable s tudies with clinically localized prostate cancer, RIS had a true-posit ive rate of 92% (12/13). In eight patients with previous incidental ca rcinoma detected during transurethral resection undertaken for clinica lly benign disease, there were 86% true-positive results (6/7) and one true-negative result, which were confirmed by systematic needle biops ies. In six patients with evidence of local recurrence after a previou s radical prostatectomy, the true-positive rate was 100% (6/6), which was confirmed by raised or rising prostate-specific antigen levels (PS A) and/or by biopsy. In the eight patients with known metastases, the disease was visualized in 4/4 with progression but not in the 3/3 with regression; one patient demonstrated regressing disease as determined by PSA levels. The overall accuracy was 92%. Conclusion: RIS with Tc- 99m CYT-351 is capable of providing good quality images and yielding c linically useful information safely. It has a potentially important cl inical role for patients with rising PSA levels but negative images by conventional modalities.