Ultrasensitive assay of prostate-specific antigen for early detection of residual cancer after radical prostatectomy

Objectives: Perhaps the greatest value of PSA determination in the treatment of prostate cancer is in determining persistent disease after a radical prostatectomy. We investigated the ability of an ultrasensitive PSA assay to detect residual prostate cancer in men at risk for recurrence after a radical prostatectomy. Methods: Using the Immulite third-generation PSA assay (detection limit, less than 0.003 ng/mL), and the standard IMx PSA assay, we determined PSA levels in 205 serum samples serially obtained from 34 men after a radical prostatectomy. The average days from surgery to serum sampling was 430 (range, 63 to 1296). Patients were classified as having nonaggressive or aggressive cancers, based on clinicopathologic findings. A biochemical relapse was arbitrarily defined. Results: All 17 patients with nonaggressive cancers had PSA values of less than 0.02 ng/mL throughout the sampling period. Two of these patients (12%) had 2 or more consecutive PSA increases and were considered as a biochemical relapse. In contrast, 14 (82%) of 17 patients with aggressive cancers fit criteria of a biochemical relapse. All of the relapses were identified within 2 years after surgery. The IMx assay detected only 7 biochemical relapses during the same sampling period. Conclusions: Using the Immulite PSA assay, relapse detection times may be shortened allowing for most serological recurrences to be detected within 2 years after a radical prostatectomy. Patients with aggressive cancers may require frequent postoperative PSA determinations with a highly sensitive PSA assay which would allow early intervention when treatments for relapse are effective.