Feasibility and Toxicity of Degarelix for Prostate Downsizing Prior to Permanent Seed Prostate Brachytherapy

Inclusion Criteria: * Histologic diagnosis of prostate cancer * Favorable risk disease (cT1 or T2a, Gleason score (GS) 6, and Prostate Specific Antigen (PSA) \< 10 ng/mL) * Low-tier intermediate risk disease (cT2c,GS=6,and PSA 10-15 ng/mL, OR GS=7 and PSA \< 10 ng/mL) * Intermediate risk disease AND androgen deprivation therapy recommended by the treating physician for oncologic reasons such as (≥ 50% positive biopsy cores,cT2c,PSA 15-20 ng/mL,GS=7) * Patient requires baseline planning trans-rectal ultrasound for the purposes of prostate brachytherapy, showing prostate volume \> 40 mL and pubic arch interference (not required for those requiring androgen ablation for oncologic reasons) Exclusion Criteria: * castrate serum testosterone level * previous or concurrent pelvic radiotherapy * unable to give written informed consent * contraindications to permanent seed prostate brachytherapy or to androgen deprivation therapy * prior treatment for prostate cancer * prior trans-urethral resection of the prostate * previous therapy with a 5-α reductase inhibitor, anti-androgen agent, or LHRH agonist * previous therapy with degarelix