Comparison of serum PSMA, PSA levels with results of cytogen-356 ProstaScint® scanning in prostatic cancer patients

BACKGROUND. Stored serum from clinical trial cases undergoing ProstaScint (CYT-356) scanning were available for Prostate Specific Membrane Antigen (PSMA) assay. Prostate Specific Antigen (PSA) levels had already been determined. This provided an opportunity to see what correlations existed between the serum markers and the ProstaScint® scan. A group of patients had the studies preprostatectomy, whereas another group had the studies postprostatectomy. METHODS. The scan results, serum PSA, serum PSMA, and clinical data were separately analyzed. PSMA serum levels were determined by Western blot. RESULTS. Preoperatively, radical prostatectomy patients showed a correlation between serum PSA or PSMA levels and the ProstaScint® scan in the total group (n = 86), or in an untreated group (n = 38). Preoperatively, PSMA correlated with the pathological stage, whereas PSA correlated with the scan. Postoperatively, only PSMA serum levels correlated with the scan in an untreated group (n = 40). CONCLUSIONS. Preoperatively or postoperatively, Western blot PSMA serum levels predict the stage of disease or local, regional, or distant metastases, as shown by ProstaScint® scan. Both the scan and the serum tests provide prognostic information and evaluate the extent of disease to a more significant degree than previously possible.