Evaluating the order of hormone therapy drugs for patients with prostate cancer

This study evaluated the order of treatment with two different hormone therapy drugs in patients with castration-resistant prostate cancer that has spread. This study found that treatment with abiraterone acetate (Yonsa) then enzalutamide (Xtandi) delayed cancer growth or spread longer than the same drugs in the opposite order.

Prostate cancer can sometimes spread outside of the prostate and become castration-resistant. This means that the cancer stops responding to treatment that lowers hormone levels. The cancer may also stop responding to a certain drug over time. When this happens, a patient may need to be switched to a second-line drug.

Enzalutamide and abiraterone acetate are two drugs frequently used for hard-to-treat prostate cancer. These drugs interfere with how the body responds to androgens (male hormones). Prostate cancer that stops responding to one of these drugs may also stop responding to the other. It is unclear if the order in which these drugs are given affects patient outcomes.

This study followed 202 patients with hard-to-treat prostate cancer. 101 patients started abiraterone (Group A) and 101 patients started enzalutamide (Group B). When their disease progressed, patients were switched to the other drug for second-line treatment. Patients were followed for an average of 30.7 months.

In this study, disease progression was measured by tumor size or levels of a molecule called PSA. High levels of PSA means that the cancer is growing or spreading. A PSA response is when a drug lowers PSA levels. This means that the treatment is working.

Overall, first-line treatment delayed disease progression by 11.2 months (Group A) and 10.2 months (Group B). 73% of patients then switched over to the other group for second-line treatment. 

Significantly more patients in Group A had a PSA response compared to Group B (36% vs. 4%). On average, initial treatment with abiraterone significantly delayed disease progression compared to enzalutamide (19.3 months vs 15.2 months). 

Overall, 15% (Group A) and 20% (Group B) of patients had serious side effects. The most common side effect was high blood pressure (27% vs. 18%). Fatigue was also common (10% vs. 4%).

This study found that patients had a better response to abiraterone acetate first, followed by enzalutamide. The authors suggest that enzalutamide was more effective as a second-line treatment.

There are other second-line treatment options such as radiation or chemotherapy. More studies are needed to compare enzalutamide to other second-line treatments.