Sensitive prostate specific antigen measurements identify men with long disease-free intervals and differentiate aggressive from indolent cancer recurrences within 2 years after radical prostatectomy

Purpose: Commonly available prostate specific antigen (PSA) assays have detection limits of greater than 0.05 ng./ml., limiting their ability to identify residual or recurrent prostate cancer after radical prostatectomy or to provide prognostic information within the first several years after surgery. We investigated the ability of a sensitive PSA assay to identify residual prostate cancer and men at risk for early recurrence after radical prostatectomy. Materials and Methods: We measured PSA in 1,037 serum samples obtained serially from 127 men after radical prostatectomy using the IMMULITE* third generation PSA assay. Results: The IMMULITE PSA assay has an analytical sensitivity of less than 0.002 ng./ml. and a clinically useful decision threshold of 0.01 ng./ml. With this assay our patients were classified into 3 groups: 1) 50 with a postoperative baseline PSA of less than 0.01 ng./ml. that did not change during an average of 36 months postoperatively, 2) 66 with increasing PSA that exceeded 0.01 ng./ml. in all cases by 30 months postoperatively (20 with clinical cancer recurrences) and 3) 11 with slowly increasing PSA of greater than 0.01 but less than 0.02 ng./ml. at an average of 36 months postoperatively. Conclusions: The IMMULITE PSA assay provides clinically useful information not previously available from PSA assays with conventional sensitivity, which is highly predictive of cancer activity in patients within 2 years after radical prostatectomy.