PROSTATIC RADIOIMMUNOSCINTIGRAPHY - PRELIMINARY-RESULTS USING TECHNETIUM-LABELED MONOCLONAL-ANTIBODY, CYT-351

Objective To investigate the clinical application of a new technique f or imaging prostatic malignancy using planar imaging and single-photon emission tomography (SPET) with technetium-99m-labelled antibody to a prostatic cell surface membrane antigen. Patients and methods Prostat ic malignancy was imaged by radioimmunoscintigraphy (RIS) using a Tc-9 9m-labelled monoclonal antibody, CYT-351, raised against a newly ident ified membrane antigen present in normal and malignant prostatic tissu es, The protocol involved taking serial images and assessing the chang es in activity, as the uptake of specific antibody increased with time and non-specific uptake decreased, Data from planar images were colle cted at 10 min, 6 and 24 h after injection with antibody, and by SPET at 6 and 24 h using a Siemens Orbiter Large Field of View gamma camera , Twenty-two RIS scans were evaluated, which included six patients wit h clinically localized disease, six patients with previous incidental carcinoma at prostatectomy for apparently benign disease, four patient s with evidence of local recurrence after radical prostatectomy and si x patients with metastatic disease. Results Primary tumours and second ary lymphatic and bone metastases were demonstrated. Only one minor si de-effect was experienced. Conclusion This RIS technique was capable o f imaging primary prostatic malignancy and metastatic disease in lymph nodes and bone. Its clinical application remains to be defined, but p otentially it provides a new means for tumour staging based upon tissu e characterization. It may be particularly useful before radical prost atectomy and it is capable of imaging local recurrence following radic al treatment of localized disease. Future applications include monitor ing the progression of disease and the response to treatment.