SAN FRANCISCO, CA USA (UroToday.com) - Data from PREVAIL, a randomized, double-blind, placebo-controlled phase III trial of enzalutamide in men with asymptomatic or mildly symptomatic chemotherapy naïve mCRPC were presented by Dr. Beer.
Enzalutamide is an androgen receptor inhibitor of AR nuclear translocation approved for use in men with metastatic castration resistant prostate cancer (mCRPC) who have received prior docetaxel chemotherapy. 1 717 patients were randomized 1:1 to enzalutamide daily or placebo, and the co-primary endpoints of overall survival (OS) and radiographic progression-free survival (PFS) were examined.
|Treatment with enzalutamide significantly improves OS and PFS in men with chemotherapy-naive mCRPC|
PREVAIL was halted at the interim analysis given the significant benefit observed with enzalutamide. Treatment groups were well balanced for baseline disease burden and comorbidities. Median duration of enzalutamide treatment was more than 3-fold longer than for placebo (16.6 vs 4.6 months). Enzalutamide was associated with a 30% reduction in risk of death (OS: HR 0.70 [95 CI 0.59-0.83]) and an 81% reduction in the risk of radiographic progression (PFS: HR 0.19 [95 CI 0.15-0.23]) at interim analysis. The radiographic PFS and OS benefits were consistent across subgroups. Because a majority of the patients in the trial are still alive, only 3.2% of patients are contributing data to overall survival estimates.
Enzalutamide resulted in an objective soft tissue response rate of 59%, and delayed the median time to chemotherapy by 17 months. Further, the time to PSA progression was 11.2 vs 2.8 months in favor of enzalutamide. Subsequent therapies were used more commonly in the placebo group (70.3% vs 40.3%). Median OS was 32.4 vs 30.2 months in patients treated with enzalutamide or placebo, respectively. Major reported side effects included seizure events in two patients. Serious adverse events occurred in 32% and 26.8% of patients treated with enzalutamide and placebo, respectively. Grade 3+ adverse events occurred in 42.9% vs 37.1%. Discontinuations due to adverse drug events were equal between patients treated with enzalutamide and placebo (5.6% vs 6.0%). Fatigue, back pain, constipation, and arthralgias were the most frequently reported adverse events associated with enzalutamide therapy.
Highlights of a presentation by Tomasz Beer, MD at the 2014 Genitourinary Cancers Symposium - January 30 - February 1, 2014 - San Francisco Marriott Marquis - San Francisco, California USA
Knight Cancer Institute, Portland, OR USA
Written by Jeffrey J. Tomaszewski, MD medical writer for UroToday.com
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