Minimal percentage of dose received by 90% of the urethra (%UD90) is the most significant predictor of PSA bounce in patients who underwent low-dose-rate brachytherapy (LDR-brachytherapy) for prostate cancer

We studied 200 consecutive patients who received LDR-brachytherapy between July 2004 and November 2008. Of them, 137 patients did not receive neoadjuvant or adjuvant androgen deprivation therapy. One hundred and forty-two patients were treated with LDR-brachytherapy alone, and 58 were treated with LDR-brachytherapy in combination with external beam radiation therapy. The cut-off value of PSA bounce was 0.1？ng/mL. The incidence, time, height, and duration of PSA bounce were investigated. Clinicopathological and postdosimetric parameters were evaluated to elucidate independent factors to predict PSA bounce in hormone-na？ve patients who underwent LDR-brachytherapy alone.Fifty patients (25%) showed PSA bounce and 10 patients (5%) showed PSA failure. The median time, height, and duration of PSA bounce were 17？months, 0.29？ng/mL, and 7.0？months, respectively. In 103 hormone-na？ve patients treated with LDR-brachytherapy alone, and univariate Cox proportional regression hazard model indicated that age and minimal percentage of the dose received by 30% and 90% of the urethra were independent predictors of PSA bounce. With a multivariate Cox proportional regression hazard model, minimal percentage of the dose received by 90% of the urethra was the most significant parameter of PSA bounce.Minimal percentage of the dose received by 90% of the urethra was the most significant predictor of PSA bounce in hormone-na？ve patients treated with LDR-brachytherapy alone.Several investigators have reported PSA (prostate-specific antigen) bounce, a transient PSA elevation that is frequently observed after low-dose-rate brachytherapy (LDR-brachytherapy) [1-10]. Although the factors that affect PSA fluctuation after LDR-brachytherapy are unclear, multiple factors including age, prostatitis due to radiation or urinary tract infection, acute urinary retention, laboratory error, instrumentation, ejaculation, radiation proctitis, and testosterone recovery after androgen deprivation therapy (ADT)