Enzalutamide as monotherapy for advanced prostate cancer: why not?

Prostate cancer (PCa) is an androgen-dependent disease. In some cases, the tumor progresses despite castration levels of serum testosterone, turning into the lethal phenotype of castration-resistant prostate cancer (CRPC), still driven by androgens and requiring the androgen receptor as a driver and responsible for progression. Enzalutamide, an androgen receptor inhibitor, is indicated for the treatment of metastatic CRPC, asymptomatic or mildly symptomatic, after failure of androgen deprivation. In both clinical trials that led to its approval, Enzalutamide was administered with an LHRH analog, setting the "standard of care" for its use. In this article we evaluate the available evidence and theory on the use of Enzalutamide as monotherapy.

Androgen deprivation well-known adverse events, together with the fact that its clinical benefit is moderate and the evidence strength is weak, and the direct negative impact on the common chronic conditions affecting this age-group led to investigation of Enzalutamide without LHRH analogs.

There are clinical trials on Enzalutamide monotherapy for hormone-sensitive prostate cancer with favourable outcomes, and there are also two ongoing studies in different advanced PCa scenarios, the PROSPER and EMBARK trials. It would be up to now a safe alternative, with less toxicity and lower costs.

It is mandatory to validate these early results on the use on Enzalutamide monotherapy for advanced prostate cancer, hormone-sensitive or castration resistant, metastatic or not, but in the meantime, we wonder, why not?