THE USE OF ULTRASENSITIVE PROSTATE-SPECIFIC ANTIGEN ASSAYS IN THE DETECTION OF BIOCHEMICAL RECURRENCE AFTER RADICAL PROSTATECTOMY

Objective To determine the gain in lead time obtained when using ultra sensitive prostate-specific antigen (PSA) assays in the diagnosis of b iochemical progression after radical prostatectomy. Patients and metho ds The post-operative PSA serum concentrations of 137 patients who had undergone radical prostatectomy were evaluated retrospectively. From these patients, 12 were selected who showed biochemical recurrence, as measured by the Hybritech Tandem-E Singlepoint PSA assay. Samples of the serum frozen at the time of the initial analysis were thawed and P SA values were remeasured by the Abbott IMx PSA assay and the Tandem-E Multipoint PSA assay. Analytical thresholds (zero-dose + 3 SD) for th e Tandem-E Singlepoint. IMx and Tandem-E Multipoint assay were 1.0, 0. 04 and 0.04 ng/mL, respectively, The lead time to the detection of a r ecurrence obtained when using the IMx and the Tandem-E Multipoint PSA assay was compared with that attained using the Tandem-E Singlepoint P SA assay, As a control, PSA values were determined in 58 serum specime ns of nine patients having no evidence of recurrence after radical pro statectomy. Results All 58 control specimens had PSA levels below the analytical thresholds of the three assays, except one which had a PSA serum concentration of 0.08 ng/mL, estimated by the IMx assay. When co mpared with the lead time obtained with the Tandem-E Singlepoint assay , the 12 patients with a biochemical recurrence had a median gain in l ead time of 327 days (range 60-627) with the IMx assay and of 369 days (range 60-639) with the Tandem-E Multipoint assay. Conclusion A PSA v alue >0.04 ng/mL after radical prostatectomy heralds further biochemic al progression. The use of the ultrasensitive IMx and the Tandem-E Mul tipoint assays provided more lead time, but there is no clear evidence that this gain is necessarily of benefit to the patient.