Younger Age Is Associated With Slower PSA Decline After Low-Dose-Rate Brachytherapy for Localized Prostate Cancer

To evaluate the association of age with PSA kinetics and biochemical control after low-dose-rate brachytherapy (LDR-BT).

We retrospectively analyzed 347 patients treated with LDR-BT alone without androgen deprivation therapy between 2004 and 2015. Longitudinal PSA changes were evaluated using linear mixed-effects models with natural cubic splines for time. Age was modeled as a continuous fixed effect, including interactions with the spline terms for time. Time to PSA nadir < 0.2 ng/mL was evaluated using Cox proportional hazards models, whereas biochemical recurrence was evaluated using Fine-Gray competing-risk regression with death treated as a competing event.

Younger age was significantly associated with slower PSA decline over 5 years (p < 0.001). Each 1-year increase in age was associated with model-estimated PSA levels relative to baseline that were 4.6%, 6.4%, and 4.3% lower at 1, 3, and 5 years, respectively. This association remained significant after adjustment for Gleason grade group and treatment era and after excluding patients with PSA bounce (both p < 0.001). Median time to PSA nadir < 0.2 ng/mL was 54 months in patients aged < 65 years and 36 months in those aged ≥ 75 years. Increasing age was associated with earlier achievement of PSA nadir < 0.2 ng/mL (HR 1.04 per year, 95% CI 1.02-1.06) but was not significantly associated with biochemical recurrence.

Age was significantly associated with PSA kinetics following LDR-BT, with younger patients showing slower PSA decline and a delayed achievement of PSA nadir < 0.2 ng/mL. However, these age-related differences were not associated with biochemical recurrence.