Prostate Cancer is normally thought of as highly curable. For that minority of men who are not cured with initial treatment life eventually becomes miserable as their tumor metastases grow despite the elimination of all circulating male hormones from the blood. Those men are said to have castration resistant prostate cancer. The treatment for that entity has been hampered until recently by a lack of biologic understanding of what is going on inside those cancer cells. It turns out that the cancer itself figures out how to make male hormones (androgens, specifically testosterone) on its own; and the androgen receptor, necessary to transport that hormone from the surface of the cell to the nucleus, is synthesized in great quantity. Abiraterone, a drug that reduces the intra-prostatic synthesis of androgens, was released recently and is highly effective for short periods of time. In a recent New England Journal of Medicine article Scher et al report on the use of Enzalutamide. That drug reduces the amount of androgen receptor produced by the cancer cell. In a large randomized trial Enzalutamide was found highly effective in preventing worsening of castrate resistant prostate cancer. Researchers thought it should work, and it does. Not only is it gratifying to have a theory work out (so-called proof of principle) but more importantly it helps cancer patients. The next step is to see how these two drugs, and perhaps others, can be combined to produce more long-lasting remissions in men with this dreadful variety of Prostate Cancer. This advance is very important not only for men with advanced prostate cancer but also for investigators trying to gain a deeper understanding of how cancer works. We now have a much better understanding of the several extraordinary steps the cancer cell knows how to make to free itself from the need for its fuel, male hormones made by the testis.
Update 2020: Enzalutamide is still being used in the treatment of hormone resistant prostate cancer. However, two newer drugs — Apalutamide and Darolutamide — have similar mechanisms of action but fewer side effects. Dr. Stark predicted in 2012 that this class of drugs would be combined with Abiraterone. That has not occurred; rather this class of drugs have been improved with newer molecules.