Time to Prostate-Specific Antigen Nadir After Radical Prostatectomy – a new potential predictive prognostic parameter and its impact on clinical outcomes

BackgroundTo investigate and validate previously published associations between time to prostate-specific antigen nadir and the time-to-nadir after radical prostatectomy with biochemical recurrence and to extend this analysis to overall survival and prostate cancer-specific mortality risk. MethodsThis is a retrospective analysis of 1796 men from the South Australian Prostate Cancer Clinical Outcomes Collaborative database treated with radical prostatectomy between 1998-2018 with available prostate-specific antigen nadir data within 1-6 months after surgery. Uni- and multivariable analyses of prostate-specific antigen nadir, time-to-nadir, biochemical recurrence and death were performed with Cox and competing risks models (adjusted for age, surgery year, tumour features and preoperative prostate-specific antigen).ResultsThe univariable analysis demonstrated those with shorter time-to-nadir <3 months had a decreased risk of biochemical recurrence (log-rank, p=0.0098) compared to those with longer time-to-nadir 3-6 months. For men with a time-to-nadir <3 months, a Log-rank test showed a decreased risk of prostate cancer-specific mortality (p=0.026) compared to time-to-nadir 3-6 months, without a difference in overall survival. Multivariable competing risk analyses indicated that biochemical recurrence was more likely when time-to-nadir was 3-6 months compared to <3 months (sHR=1.43, CI 1.01-2.02, p=0.04).ConclusionsAmong men undergoing radical prostatectomy, a shorter post-operative time-to-nadir <3 months is associated with decreased risk of biochemical recurrence compared to time-to-nadir 3-6 months. Following adjustment for confounders and competing risks, there was no significant difference in time-to-nadir for mortality outcomes.