The effect of androgen deprivation therapy on prostate cancer-specific mortality in high-risk prostate cancer: Patients treated with low dose-rate brachytherapy without supplementary external beam radiotherapy.

e550 Background: Androgen deprivation therapy (ADT) is a mainstay accompaniment of external beam radiotherapy (EBRT) for treating high-risk prostate cancer (HPCaP). Both low dose-rate brachytherapy (LDR) as the sole method of radiotherapy and the need for ADT in conjunction with it are relatively unexplored with HRCaP. We present an inception cohort study of HRCaP patients treated with LDR alone with or without ADT. Methods: The study includes 515 patients with HRCaP according to NCCN guidelines. They were treated with I-125 LDR alone to a dose of 144 Gy with lateral, superior, and inferior margins of at least 5 mm (medin D90 = 149.39 Gy). The association of prostate cancer-specific mortality (PCSM) with pre-treatment variables was assessed with Fine and Gray regression with non-PCSM mortality treated as a competing event. PCSM rates were calculated using the cumulative incidence method. Results: The median age is 70 years. The median f/u is 48.9 months. Fifty-four percent were Gleason 7, 28% were Gleason 8, and 11% were Gleason 9. Fifty-three percent received ADT for a median duration of 6 months (range = 1-32 months). At 5 years, the PCSM rate was 1.2 % for LDR and 4.2% for LDR + ADT, and at 10 years, the PCSM rate for LDR was 3.3% and 4.2% for LDR + ADT (p = 0.34). Table 1 shows the association of pre-treatment factors with PCSM. Conclusions: ADT does not affect PCSM for HRCaP patients. Further studies should be done to explore if ADT is necessary with LDR for HRCaP. [Table: see text]