Summary
Participants are invited to take part in this research study to test a new treatment combination for prostate cancer. This is because they have cancer that started in the prostate and has spread to other parts of their body. This is known as metastatic prostate cancer. Current treatment for newly diagnosed metastatic prostate cancer involves androgen deprivation therapy(ADT).
Androgen deprivation therapy has two components:
1. The main component is by stopping the release of androgen from the testicles. This is mainly done by using drugs that prevent the testicles from making androgens, and therefore reducing the levels of androgens in the body to low levels. These drugs are called luteinising hormone releasing hormone analogues (LHRHA). These drugs are given as injections. This is usually part of the standard initial treatment for men in your situation. The other way of reducing androgen production by the testicles is with a surgical operation to remove both testicles. This is not part of the trial. If participants have already had this surgical procedure or it is planned to be done, they will not need to be on LHRHA, but can still take part in this study.
2. The second component of ADT is to block the effects of androgens produced in other parts of the body with antiandrogen drugs. Antiandrogen drugs block testosterone and related androgens from attaching to molecules in the cancer cell called 'androgen receptors'. Blocking this attachment prevents androgens from having their effect. This might provide additional benefit in treating the cancer although this has not yet been proven. Several different types of antiandrogen drugs are available for use already. Enzalutamide is a new antiandrogen that is not yet approved for use in Australia.
This study will compare the effectiveness of enzalutamide versus the currently available antiandrogen drugs when used on a background of treatment with a LHRHA (or surgical removal of the testicles). The main aim of the study is to see which of these combinations is best at improving the survival of men in this situation. Recent studies show promising results with the use of enzalutamide in participants who had been treated with androgen deprivation therapy and were no longer responding to the standard antiandrogens, this is known as castrate resistant prostate cancer (CRPC), which is a more advanced stage than the type of metastatic prostate cancer being studied here. With this stage of metastatic prostate cancer there is no evidence yet on which treatment is best to treat it. To do this, a total of 1100 participants will participate where half the participants on the study will receive enzalutamide with a LHRHA or surgical operation to remove both testicles and the other half (550 participants) will receive already available antiandrogens (but not enzalutamide) with a LHRHA or surgical operation to remove testicles. All participants on this study will receive active therapy and no placebo treatment will be used. The study is open label, meaning that both the participants and the investigators will know the treatment the participant will receive.