Efficiency of ultrasensitive prostate-specific antigen assay in diagnosing biochemical failure after radical prostatectomy

Background: Ultrasensitive prostate-specific antigen (PSA) is a significant serum biomarker for identifying the PSA nadir and early biochemical failure after radical prostatectomy (RP). We assessed the efficiency of ultrasensitive PSA assay in the follow-up after RP. Methods: We generated longitudinal ultrasensitive PSA data using a computer program assuming that patients experienced biochemical failure after RP. The simulation experiments, based on several different scenarios, were performed to assess the sensitivity and specificity in the diagnosis of biochemical failure using ultrasensitive PSA values and to estimate the lead time, which is the time advantage of detecting positivity for biochemical failure using the ultrasensitive PSA values compared with conventional PSA assay. We validated the sensitivity, specificity and lead time using actual follow-up data of 182 patients receiving RP. Results: It was suggested that the sensitivity obtained from the actual data was more similar to that obtained using ultrasensitive PSA with an exponential increase than with a linear increase in the simulation experiments. Diagnosing biochemical failure based on two consecutive increases in the ultrasensitive PSA values was not recommended. Of nonbiochemical failure patients, 9.4% showed four consecutive increases in their ultrasensitive PSA values. Average lead time in the actual data was 11.2 months (SD: 10.1). Conclusions: For an accurate diagnosis of biochemical failure, our findings suggest the importance of a certain duration of follow-up and exclusion of false-positive results afterwards.