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Radioscintiscanning of the prostate has been unsuccessfully attempted in the past 25 years. [65.sup.zinc] was an early possibility but could not provide satisfactory clinical images. Although cellular secretory products of the prostate, such as acid phosphatase and prostatic specific antigen (PSA), were labeled with radioisotopes, final results did not yield acceptable outcomes. More recently, a monoclonal antibody (MoAb), 7E11-C5, to the membranes of the LNCaP (prostate cancer) cell line has been developed and radiolabeled with ... In. This agent., designated as CYT-356, has successfully undergone human Phase I and II trials in which suitable radioimmunoscintography was achieved detecting prostate cancer foci in the prostate, pelvic lymph nodes, bones, and soft tissues. Generally acceptable sensitivity (>50%) and specificity (>90%) levels have been observed in the initial trials, suggesting a useful role for preoperative evaluation and follow-up for postoperative pelvic recurrence or other metastases. Two national Phase Ill trials are about to be completed in addition to a repeat administration study. The epitope detected by MoAb 7E11-C5 or CYT 356 has recently been shown to be present in normal male serum, seminal fluid, and benign prostate enlargement and in higher levels in clinically advanced prostate cancers, Stages C, D1, and D2 (T2-T3, T4). A second-generation MoAb to CYT-356 (7E11-C5.3)-defined antigen has been developed and is being tested as a potential prostate cancer serum marker. Cancer 1995; 75:1819-22.

Background. In hopes of limiting low-yield prostate biopsies, results of digital rectal examination (DRE), transrectal ultrasound (TRUS), prostate specific antigen (PSA) and age-related PSA values, gland-volume-adjusted PSA levels, and longitudinal PSA changes were analyzed to identify their cost-effectiveness as prognostic indicators in screening, biopsy, and follow-up of patients with prostate cancer. Methods. Twenty-nine hundred men with complete data sets from an initial cohort of 2999 men with an annual follow-up for up to 5 years were examined. Intrapatient PSA and gland-volume variability, optimal PSA operating points (o.p.), and test performance scores were determined for each parameter. Decision analysis was then applied retrospectively to each parameter to determine the cancer detection yield, biopsy requirements, and costs for commonly used detection strategies. Results. For the initial screening decision, the optimal PSA o.p. was 3.0 ng/ml but increased to 5.0 ng/ml in combination with DRE, whereas age-related PSA performed no better than did PSA. The mean intrapatient variability in TRUS gland volume (+5.5 cc) relative to mean volume (34 cc) was 16%, which was less than the 28% (0.64/2.3ng/ml) relative variability for PSA. For biopsy decisions, using PSA density (PSAD) with a level of 0.12 ng/ml/cc there was no significant difference in accuracy compared with the systematic biopsy of all patients with elevated PSA or age-related PSA levels. Rather than perform systematic biopsy on all patients with PSA levels greater than 4 ng/ml, decision analysis showed that a 16-55% reduction in biopsies could be achieved with a respective cancer loss of 4-25% by limiting biopsy to patients with an increased PSAD level and/or abnormal results of DRE. Using age-related PSA criteria in combination with DRE reduced biopsies by achieved but resulted in minimal cost reductions. The greatest biopsy reduction relative to cancer yield and lowest cost per cancer detected occurred with PSAD-driven biopsy strategies. During follow-up, longitudinal changes in absolute PSA and PSAD levels were significantly better (P < 0.05) than the percentage change in PSA levels per year. Conclusions. Cost-effective prostate cancer detection with PSA as a parameter is better achieved if screening and biopsy decisions are not linked intimately. A tailored-biopsy approach for patients with disproportionately elevated PSA levels of suspicious DRE results in the greatest biopsy reduction by selecting lower risk groups for more conservative follow-up.

Background. Different indexes that may enhance the early detection capability of prostate specific antigen (PSA) have been proposed. In addition to the indexes relating to the normal PSA level, there are data suggesting the usefulness of the PSA level relative to prostate gland volume (PSA density), age-referenced PSA level, and PSA change. Little research comparing the sensitivity and specificity of these measures in the same population has been reported. Methods. All subjects were participants in the American Cancer Society National Prostate Cancer Detection Project. Specificity was studied in 2011 men without prostate cancer, and sensitivity was determined for 171 men with prostate cancer. Results. Prostate specific antigen change showed the highest specificity (96.4%), and PSA density the lowest (85.3%). The most sensitive index was PSA density, which was positive for 74.7% of the 171 cases of known cancer. A PSA change of more than 0.75 ng/ml per year was the least sensitive index (54.8%). Sensitivity and specificity varied in a narrow range. Improved performance in specificity was achieved only with the loss of sensitivity. Conclusions. None of the alternative indexes commonly used in general early detection practice demonstrated particular advantage when compared with the normal PSA concentration, defined as no more than 4.0 ng/ml.