Presenter(s)
Y. Nakai1, K. Onishi1, Y. Kaori2, F. Isohashi2, and N. Tanaka II1; 1Department of Urology, Nara Medical University, Kashihara, Japan, 2Department of Radiation Oncology, Nara Medical University, Kashihara, Japan
Purpose/Objective(s): A low prostate-specific antigen (PSA) nadir after low-dose-rate brachytherapy (LDR-BT) is a well-established predictor of favorable oncologic outcomes in prostate cancer. Although patient age has been evaluated as a potential prognostic factor, its independent association with oncologic outcomes remains inconsistent. We hypothesized that younger age is associated with delayed PSA decline but not inferior oncologic outcomes. Therefore, we evaluated the association between age and longitudinal PSA kinetics after LDR-BT and examined whether age-related differences in PSA decline translate into differences in biochemical or disease-free recurrence.
Materials/Methods: We retrospectively analyzed 347 patients treated with LDR-BT alone without androgen deprivation therapy between 2004 and 2015 at a single institution. Longitudinal PSA trajectories were assessed using nonlinear mixed-effects models. Time to PSA nadir <0.2 ng/mL was estimated using Kaplan–Meier methods and compared using log-rank trend tests. Multivariable Cox proportional hazards models were used to identify factors associated with time to PSA nadir <0.2 ng/mL, biochemical recurrence (BCR; Phoenix definition), and disease-free recurrence (DFR). Median follow-up was approximately 7–8 years.
Results: Age significantly modified the nonlinear trajectory of PSA decline (p<0.001), with younger patients demonstrating a more gradual reduction over time. Increasing age was associated with earlier achievement of PSA nadir <0.2 ng/mL (median 54, 48, 42, and 36 months for patients aged <65, 65–69, 70–74, and =75 years, respectively; trend p<0.001). In multivariable analysis, older age independently predicted earlier PSA nadir achievement (hazard ratio 1.043 per year increase, 95% confidence interval 1.024–1.062; p<0.001). However, age was not associated with BCR or DFR.
Conclusion: Age significantly influences longitudinal PSA kinetics after LDR-BT, with younger patients exhibiting delayed PSA decline. However, these differences do not translate into inferior oncologic outcomes. Careful interpretation of PSA kinetics according to patient age may therefore be warranted.