Objectives: We have compared the ability of an ultrasensitive prostate specific antigen assay and a regular PSA assay to identify relapse and cure rates of prostate cancer patients after radical prostatectomy, during a 5-year follow-up period.
Design and methods: We measured PSA by an ultrasensitive assay (detection limit 0.001 ng/mL) and a conventional PSA assay (detection limit 0.1 ng/mL) in serial serum samples obtained from 197 patients who have undergone radical prostatectomy.
Results: Based on ultrasensitive PSA analysis, we have identified three groups of patients: 62% of patients did not show any significant changes in serum PSA; 15% of patients demonstrated slow PSA increases over time but none of the measurements exceeded 0.1 ng/mL within 4 years; and 23% of the patients had relatively significant increases of serum PSA and were classified as having 'fast relapse'. The vast majority of these patients were subsequently identified to have relapse by the regular PSA assay. The ultrasensitive PSA assay detected relapse by an average of eighteen months earlier than the conventional PSA method. Fast relapsing patients were associated with other prognostic indicators of the disease including pre-operative PSA, tumor volume, Gleason score, clinical stage, surgical margin positivity, periprostatic tissue involvement, capsular invasion and seminal vesicle invasion. The group with slowly rising PSA had prognosis which was between the patients in remission and fast relapsing patients.
Conclusions: The use of ultrasensitive PSA analysis for monitoring patients after radical prostatectomy provides earlier detection of relapse (by 18 months) and identifies three distinct groups of patients. Fast relapsing patients should be good candidates for early therapeutic interventions.