Changes in alkaline phosphatase levels in patients with prostate cancer receiving degarelix or leuprolide: results from a 12-month, comparative, phase III study

OBJECTIVE To compare the activity of degarelix, a new gonadotrophin-releasing hormone (GnRH) blocker, with leuprolide depot 7.5 mg in the control of total serum alkaline phosphatase (S-ALP) levels in patients with prostate cancer. PATIENTS AND METHODS In the randomized, phase III trial (CS21), patients with histologically confirmed prostate cancer (all stages), were randomized to one of three regimens: degarelix subcutaneous 240 mg for 1 month followed by monthly maintenance doses of 80 mg or 160 mg, or intramuscular leuprolide 7.5 mg/month. Patients receiving leuprolide could also receive antiandrogens for flare protection. We report exploratory S-ALP analyses from CS21, focusing on the comparison of degarelix 240/80 mg with leuprolide 7.5 mg, in line with the recent approvals of this dose by the USA Food and Drug Administration and the European Medicines Agency. RESULTS Overall, 610 patients were included, with a median age of 73 years and median prostate-specific antigen (PSA) level of 19.0 ng/mL. Baseline S-ALP levels were high in metastatic patients and highest in patients with metastatic disease and a haemoglobin level of < 13 g/dL. In metastatic disease, after initial peaks in both groups, S-ALP levels were suppressed below baseline with degarelix but were maintained around baseline with leuprolide. The late rise in S-ALP seen with leuprolide was not apparent with degarelix. The pattern of S-ALP response was similar in patients with a baseline PSA level of >= 50 ng/mL. Between-treatment differences in patients with metastatic disease and those with a PSA level of >= 50 ng/mL were significant at day 364 (P = 0.014 and 0.007, respectively). CONCLUSION Patients with metastatic disease or those with PSA levels of >= 50 ng/mL at baseline had greater reductions in S-ALP levels with degarelix than with leuprolide. Patients in the degarelix group maintained S-ALP suppression throughout the study, in contrast to those in the leuprolide group. This suggests that degarelix might offer better S-ALP control than leuprolide and might prolong control of skeletal metastases, compared with GnRH agonists, over a 1-year treatment period.