Enzalutamide for Metastatic Hormone-Sensitive Prostate Cancer

The Pharmaceutical Benefits Scheme (PBS) listing for enzalutamide has recently been expanded. Enzalutamide is an oral inhibitor of androgen receptor signalling. It is now subsidised for the treatment of metastatic hormone-sensitive prostate cancer, in addition to castration-resistant metastatic and non-metastatic prostate cancer.

The ARCHES trial investigated the safety and efficacy of enzalutamide in the treatment of metastatic hormone-sensitive prostate cancer. Patients were randomised to receive enzalutamide (160mg daily) or placebo, with both groups also receiving androgen deprivation therapy (ADT). Patients in the enzalutamide group had a 61% reduced risk of radiographic disease progression or death compared to the placebo group. The ENZAMET trial further supports the efficacy of enzalutamide in this patient group. In this trial, patients were randomised to receive ADT plus either enzalutamide or standard care with a nonsteroidal antiandrogen (e.g. bicalutamide, nilutamide, or flutamide). After a median follow-up of 68 months, the median overall survival was not reached. However, the five-year overall survival was significantly higher in the enzalutamide group (67% versus 57%).

The safety of enzalutamide in the ARCHES trial was consistent with the findings of earlier studies conducted in castration-resistant prostate cancer. Adverse effects of grade 3 or higher were slightly more common in the placebo group (25.6% versus 24.3%). The most common adverse effects reported in the active group included hot flushes, fatigue, and musculoskeletal events. No unexpected adverse events were reported.