Prostate cancer imaging with a new monoclonal antibody: a preliminary report.

Background: Optimal treatment of prostate cancer depends on accurate staging. Computed tomography (CT) and magnetic resonance imaging have severe limitations, and standard bone scanning can show only destructive osseous metastases. A radiolabeled antibody specific to prostatic adenocarcinoma could theoretically find evidence of soft-tissue metastases and lymph node involvement.

Methods: An immunoconjugate (CYT-356) consisting of a murine monoclonal antibody against human prostatic adenocarcinoma bound to a linker-chelator and radiolabeled with indium 111 was administered intravenously to seven patients with documented Stage D adenocarcinoma of the prostate. Planar imaging was done on days 1, 2, and 3 after injection. The CYT-356 scans were compared with standard technetium Tc99m sulfur colloid bone scans and CT scans.

Results: Optimal imaging results were obtained on the 72-h scans. All patients had lesions on both the 99mTc-sulfur colloid bone scan and the CYT-356 scan. The location of the lesions correlated to a great extent. Two patients had positive lesions biopsied, and both biopsies showed the presence of metastatic prostatic carcinoma. There were no side effects from administration of the antibody.

Conclusion: In this preliminary study, CYT-356 scanning appears to be a promising agent to accomplish specific staging of prostatic carcinoma.