A Case of Switching from GnRH Agonist to Antagonist for Castration Resistant Prostate Cancer Control

Abstract

GnRH antagonist and GnRH agonist are widely used as androgen deprivation therapy for metastatic prostate cancer. A previous report demonstrated that patients with PSA levels of >20 ng/mL using GnRH antagonists showed favorable outcomes in comparison to those using GnRH agonists. An 82-year old male patient with edema, a stony hard nodule on his prostate, and an initial PSA level of 6,717 ng/mL was referred to our hospital due to suspected prostate cancer. He received prostate needle biopsy and was diagnosed with prostate cancer with bone metastasis, with a Gleason Score of 4 + 4 = 8. He was then treated with a GnRH agonist (leuprorelin acetate) and bicalutamide from July 2015. Although his PSA level decreased to 582.0 ng/mL in December 2015, his PSA level gradually increased and CRPC developed. He indicated that he did not wish to take 2nd generation anti-androgen drugs or receive systemic chemotherapy. We introduced a GnRH antagonist (degarelix) in February 2015; his PSA level did not change and his CRPC was controlled. We herein report a case in which changing a GnRH agonist to a GnRH antagonist contributed to CRPC control.

Keywords

• Degarelix
• GnRH antagonist
• CRPC