Salvage brachytherapy for recurrent prostate cancer after definitive radiation therapy: A comparison of low-dose-rate and high-dose-rate brachytherapy and the importance of prostate-specific antigen doubling time

Abstract Background Salvage brachytherapy is a treatment option for patients with locally recurrent prostate cancer after primary radiation therapy. We reviewed our experience using low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy to compare the outcome and toxicity profiles of each approach in the salvage brachytherapy setting. Methods and Materials Ninety-eight patients with biopsy-proven locally recurrent prostate cancer who underwent salvage brachytherapy (LDR = 37; HDR = 61) following an initial course of definitive radiotherapy between 4/2003 and 4/2015 were retrospectively reviewed. All patients underwent salvage brachytherapy using LDR or HDR. Androgen deprivation therapy was used in 45% of the patients. Prostate-specific antigen (PSA) failure was determined using the Phoenix (nadir+2) definition. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4 and patient-reported questionnaires. Results Median followup was 31 months. The 3-year PSA relapse-free survival (RFS) was 60.1% (95% CI, 49.6–72.5%). There was no difference between LDR and HDR brachytherapy in terms of PSA RFS ( p  = 0.84 by log-rank test). On multivariate analysis, only prostate-specific antigen doubling time (PSADT) p  = 0.002 by long-rank test). There were no statistically significant differences in toxicity between LDR and HDR brachytherapy. There was a higher peak in urinary symptoms in LDR patients; however by 24–36 months, most patients in both groups returned to baseline. Conclusions Both LDR and HDR salvage brachytherapy are an excellent treatment options for appropriately selected patients with comparable outcome and toxicity. Patients with a PSADT