Data from the TERRAIN trial support the use of enzalutamide rather than bicalutamide in patients with asymptomatic or mildly symptomatic metastatic castration-resistant prostate cancer (mCRPC), a study published the journal The Lancet Oncology has shown.1

Because enzalutamide, an oral androgen-receptor inhibitor has been shown to improve survival in two phase 3 trials and is approved for patients with mCRPC, researchers sought to compare the efficacy and safety of enzalutamide with bicalutamide in this patient population.

For the double-blind, phase 2 trial, researchers enrolled 375 patients with asymptomatic or minimally symptomatic men with prostate cancer who progressed on androgen deprivation therapy (ADT). Participants were randomly assigned 1:1 to receive enzalutamide 160 mg orally daily or bicalutamide 50 mg orally daily, in addition to ADT, until disease progression.

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Results showed that median progression-free survival was 15.7 (95% CI, 11.5 – 19.4) with enzalutamide compared with 5.8 months (95% CI, 4.8 – 8.1) with bicalutamide (HR, 0.44; 95% CI, 0.34 – 0.57; P < .0001) after a median follow-up of 20.0 months and 16.7 months, respectively.

In regard to safety, the most common adverse events in the enzalutamide or bicalutamide groups were fatigue, back pain, hot flush, nausea, constipation and arthralgia. Grade 3 or higher adverse events included hypertension hydronephrosis, back pain, pathological fracture, dyspnea, bone pain, congestive heart failure, myocardial infarction, and anemia.

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Serious adverse events occurred in 31% and 23% of patients in the enzalutamide and bicalutamide groups, respectively. Of note, 1 death in the enzalutamide group may be associated with treatment-related systemic inflammatory response syndrome.


  1. Shore ND, Chowdhury S, Villers A, et al. Efficacy and safety of enzalutamide versus bicalutamide for patients with metastatic prostate cancer (TERRAIN): a randomised, double-blind, phase 2 study [published online ahead of print January 13, 2016]. Lancet Oncology. doi: 10.1016/S1470-2045(15)00518-5.