Treatment with enzalutamide rather than bicalutamide for nonmetastatic or metastatic castration-resistant prostate cancer (CRPC) improves survival, according to results of a phase 2 clinical trial.
CRPC occurs when levels of prostate-specific antigen continue to increase after initial treatment, causing the disease to spread to other regions of the body, most commonly the bones or soft tissue. Treating CRPC most often involves the use of androgen deprivation therapy (ADT) with a second-line hormonal agent added, usually the nonsteroidal antiandrogen drug bicalutamide.
The STRIVE (Safety and Efficacy Study of Enzalutamide Versus Bicalutamide in Men With Prostate Cancer) trial compared the safety and efficacy of bicalutamide and an oral androgen receptor inhibitor, enzalutamide, for the treatment of CRPC. A total of 396 patients with metastatic and nonmetastatic CRPC were enrolled in the trial and were randomly assigned to receive either enzalutamide or bicalutamide. Both treatments were in addition to standard ADT therapy.
The authors, led by David F. Penson, MD, MPH, Department of Urologic Surgery, Vanderbilt University Medical Center, Nashville, TN, reported that the median time on treatment was longer for patients receiving enzalutamide than for those receiving bicalutamide (14.7 months vs 8.4 months). In addition, a greater percentage of patients in the enzalutamide arm continued treatment after the conclusion of study (53% vs 20%).
Median progression free-survival, which was the primary endpoint of the study, was significantly improved in patients treated with enzalutamide compared with bicalutamide (19.4 vs 5.7 months). In fact, treatment with enzalutamide was associated with a 76% reduction in progression or death compared with bicalutamide. Improvements in time on trial and PFS were consistent in both subgroups of metastatic and nonmetastatic patients treated with enzalutamide.
The numbers of adverse events associated with treatment were similar between the study arms. Enzalutamide was more commonly associated with back pain, hot flashes, falls, hypertension, dizziness and decreased appetite; whereas constipation, diarrhea, anemia, and urinary tract infection were more common in those treated with bicalutamide.
The results from the trial add to the existing body of evidence favoring enzalutamide over bicalutamide in patients with nonmetastatic or metastatic CRPC. Results were published in the Journal of Clinical Oncology.
