USE OF A NEW HYPERSENSITIVE ASSAY FOR THE DETECTION OF PROSTATE-SPECIFIC ANTIGEN IN PROSTATE-CANCER

We have developed a new hypersensitive enzyme immunoassay for prostate specific antigen (PSA) based on the (MARKIT-M PA) assay but employing a two-hour incubation of the primary monoclonal antibody. The analytical sensitivity has been determined at 0.2 ng/ml, calculated as the mean + three standard deviations of the zero calibrator. Serum PSA was measured at least one month after radical prostatectomy (nine patients) or cystoprostatectomy (six patients). Based on the PSA levels of these patients, the recommended PSA cut-off level indicative of residual disease after radical prostatectomy was 0.4 ng/ml. Increasing (> 0.4 ng/ml) PSA levels preceded recurrence by eight months in a patient who developed bone metastasis after radical prostatectomy. In two patients treated with endocrine therapy, increasing PSA levels also preceded clinical evidence of progression by between eight and nine months. The study suggests that the newly developed sensitive PSA assay allows for the identification of patients with disease progression and the early commencement of adjuvant treatment.