Response to degarelix after resistance to luteinizing hormone-releasing hormone agonist therapy for metastatic prostate cancer.

Androgen deprivation with a luteinizing hormone-releasing hormone (LH-RH) agonist is the standard treatment for patients with metastatic prostate cancer who prefer nonsurgical options. Therapy with these agents is usually successful in achieving and maintaining castrate levels (< 50 ng/dl) of serum testosterone, but failures have been reported in up to 10% of patients. Traditionally, these patients are offered surgical castration with bilateral orchiectomy. However, the novel LH-RH antagonists may offer a nonsurgical alternative. We describe two patients with advanced prostate cancer who failed to achieve castrate levels of testosterone while on an LH-RH agonist, but subsequently responded to the LH-RH antagonist, degarelix. The first patient is a 63-year-old man who was treated with leuprolide for metastatic prostate cancer. He initially responded with prostate-specific antigen (PSA) that fell to 0.6 ng/ml. However, after 15 months of therapy, his PSA rose to 18.3 ng/ml and his testosterone was noted to be 208 ng/dl. He was switched to degarelix, and 4 weeks later his testosterone was adequately suppressed at 16 ng/dl. The second patient is a 41-year-old man with metastatic prostate cancer who was started on leuprolide, but after 3 months of therapy, was found to have a rising PSA and a testosterone of 96 ng/dl. Four weeks after switching to degarelix, his testosterone was 18 ng/dl and his PSA decreased concordantly. With continued monthly injections of degarelix, his testosterone has consistently remained to be at less than 20 ng/dl over 7 months of follow-up.