The effects of bipolar androgen therapy in men with metastatic castration resistant prostate cancer

The study evaluated outcomes of bipolar androgen therapy (BAT) in men with metastatic castration-resistant prostate cancer (mCRPC) who were continuing drugs targeting androgen receptors (AR). The authors found that BAT was clinically effective in such patients.

BAT refers to sequential injections with testosterone in men who are no longer responding to androgen deprivation therapy (ADT). Testosterone is an androgen or male sex hormone. It binds to particular proteins called androgen receptors (AR) on prostate cells. This promotes the growth of prostate cancer (PC). ADT is treatment that lowers the levels of androgens such as testosterone to very low levels (castration). This includes drugs such as enzalutamide (Xtandi) and abiraterone (Zytiga).

However, mCRPC progresses to other organs despite ADT. BAT has been shown to restore the response to ADT in patients with mCRPC. However, the effectiveness of BAT followed by a 2^nd round of ADT is unclear comparing men previously treated with enzalutamide versus abiraterone.

The study included patients with mCRPC who previously received ADT. 29 were treated with abiraterone and 30 with enzalutamide. All of them received BAT every 28 days. Following BAT, patients were re-exposed to their most recent ADT.

On average, 5 BAT doses were given to the abiraterone group. 17% of patients reached PSA₅₀. PSA is a protein whose higher levels indicate PC. PSA₅₀ refers to a more than 50% reduction in PSA levels from the start of therapy.

There was a slightly higher number of patients who achieved PSA₅₀ after enzalutamide (30%) compared to abiraterone (17%). However, after a second exposure to ADT after BAT, the PSA₅₀ response was significantly higher with enzalutamide (68%) compared to abiraterone (16%). 

Also, the average time from enrollment in the trial to disease progression was significantly longer with enzalutamide (12.8 months) compared to abiraterone (8.1 months). 

The study concluded that BAT showed clinical activity against mCRPC in men under ADT. It may be more effective to restore responsiveness to enzalutamide compared to abiraterone.

This study was conducted in a single hospital. It may not be relevant to the findings in different patient populations.