Patients with metastatic hormone-sensitive prostate cancer (mHSPC) have never received androgen deprivation therapy (ADT) before, and thus are sensitive to ADT. Enzalutamide (Xtandi®) is an androgen receptor inhibitor, which is neither approved by the European Medicines Agency (EMA) nor by the US Food and Drug Administration (FDA) as an addition to first-line treatment of patients with mHSPC.

The aim of the ENZAMET trial was to compare the efficacy and safety of adding enzalutamide to testosterone suppression. Since the trial is currently ongoing, the presented data is the first interim analysis. Overall survival (OS) was statistically significantly prolonged with enzalutamide: the hazard ratio (HR) was 0.67; however, the median OS time was not estimable in either treatment group. The benefit in favour of enzalutamide has also been observed for the following secondary endpoints: prostate-specific antigen progression-free survival (PSA-PFS, HR 0.39) and clinical PFS (HR 0.40). For two of the prespecified endpoints, health-related quality of life (HRQoL) and health outcomes relative to costs, no results are available yet. According to the authors, these results will be reported separately. Among patients of the enzalutamide group who have received early docetaxel, PFS was prolonged whilst OS was not. The incidence of serious adverse events (AEs) was higher among patients of the enzalutamide group (42%) than in patients receiving standard care (34%). In patients of the enzalutamide group who received additional early docetaxel treatment, toxic effects occurred more often than in patients of the control group. Seizures occurred in seven patients receiving enzalutamide and in none of standard-care group.

Recently published results from the ENZAMET trial indicate that patients with mHSPC benefit from the addition of enzalutamide to standard first-line treatment in terms of OS and PSA-PFS. However, the administration of enzalutamide was associated with a higher rate of serious AEs as compared to standard care. Due to the ongoing status of the trial, mature final and long-term data are lacking. However, due to the nature of the open-label study design, a high risk of bias is existent and will remain even with mature data. Since final OS data and HRQoL data are not available yet, the clinical benefit for affected patients cannot be assessed. More mature data, acquired over a longer treatment duration, are required to confirm the present results.