24th Int'l Prostate Cancer Update: Abstract - Intermittent androgen deprivation with the gonadotrophin−releasing hormone (GnRH) antagonist degarelix

VAIL, CO USA (UroToday.com) - Background: For men with prostate cancer requiring androgen suppression, intermittent androgen deprivation (IAD) has been proposed as an alternative to continuous androgen deprivation (CAD).

An intermittent treatment schedule offers the potential for fewer side effects, and consequently a better quality of life. It may also offer some cost savings. Studies have compared CAD with IAD using luteinizing hormone-releasing hormone agonists. We report the results of intermittent treatment with the gonadotrophin-releasing hormone (GnRH) antagonist degarelix.

24th cap updateMethods: Eligible patients had rising prostate-specific antigen (PSA) levels after prior definitive therapy and testosterone >150 ng/dL. Men were randomized to intermittent degarelix (DI; n=177), continuous degarelix (DC; n=50) or continuous leuprolide (LC; n=182). Initial treatment was 7 months of degarelix or leuprolide after which patients with PSA <2 ng/mL discontinued therapy in the DI arm and entered a 7−month off-treatment period. Patients in the DC or LC arm continued on degarelix or leuprolide, respectively. The primary endpoint was the proportion of patients with PSA ≤4.0 ng/mL at 14 months. Non-inferiority required a lower 95% confidence interval (CI) bound of greater than -12.5%. Secondary endpoints included testosterone recovery, time to PSA >2 ng/mL and quality of life.

Results: PSA was >4 ng/mL in 2.4% and 1.3% of patients in the DC and LC arms, respectively, while none of the patients treated with DI had PSA >4 ng/mL at month 14. The lower CI limit for DI vs. CAD (DC and LC arms combined) was -0.19%; therefore non-inferiority was established. During the off-treatment period (Months 7–14), 38 (28%) patients in the DI arm had PSA >2 ng/mL and 35 (26%) patients received additional doses of degarelix. In the DI arm, median (range) time to testosterone >50 ng/dL was 112 days (28–196 days), beginning 28 days after the last degarelix dose, and occurred in 116 (85%) patients within 6 months of stopping degarelix. Six months after stopping treatment in the DI arm, testosterone levels were >150 ng/dL in 94 (67%) patients vs. 0 (0%) and 1 (<1%) in the DC and LC arms, respectively. Sexual drive was significantly improved at month 14 for men in the DI arm compared with men continuing therapy (p=0.0271). Hot flashes were reported by 87 (50%), 26 (52%) and 110 (62%) patients in the DI, DC and LC arms, respectively. Injection site reactions occurred in 102 (58%) and 33 (66%) patients in the DI and DC groups, respectively, and 21 (12%) in the LC arm. Discontinuation due to adverse events was reported for 37 patients; 14 (8%), 5 (10%) and 18 (10%) patients in the DI, DC and LC arms, respectively.

Conclusion: The intermittent use of degarelix is non-inferior to CAD in maintaining PSA suppression when administered in a regimen of 7 months of treatment and a 7−month off-treatment period with retreatment for PSA >2 ng/mL. 50% of men in the DI arm recovered from castration by 112 days after treatment discontinuation.

Presented by E. David Crawford, Neal Shore, Celestia Higano, Anders Neijber and Vladimir Yankov at the 24th International Prostate Cancer Update - February 19 - 22, 2014 - Cascade Conference Center - Vail, Colorado USA

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