Abiraterone acetate (Zytiga) for the treatment of metastatic prostate cancer

Abiraterone acetate is available in the form of tablets, in two different doses (250 mg and 500 mg). A total of 1,000 mg is taken once a day. Abiraterone acetate is taken at least two hours after a meal and at least one hour before eating anything else. If very severe side effects arise, treatment is stopped.

The standard treatment for metastatic hormone-sensitive prostate cancer is ADT. This treatment can be supplemented with non-steroidal anti-androgens (like flutamide or bicalutamide).

In 2018, the Institute for Quality and Efficiency in Health Care (IQWiG, Germany) looked into the advantages and disadvantages of abiraterone acetate for men with metastatic hormone-sensitive prostate cancer compared to the standard treatments.

For the assessment, the manufacturer provided two studies that were still ongoing. Not all of the data from the studies could be used in the analysis. One study provided suitable data for 1,199 men. 597 of them were given abiraterone acetate and prednisone, and 602 had a placebo. Both groups also had ADT. The other study provided suitable data for 1,002 men. 500 of them had treatment with abiraterone acetate, prednisone or prednisolone and also had ADT. The remaining 502 men only had ADT.

What are the advantages of abiraterone acetate?

• Life expectancy: The studies show that abiraterone acetate can prolong life. In the larger study, about 50 out of 100 men who had the standard treatment were still alive after 3 years, while after the same period of time 70 out of 100 men who had treatment with abiraterone acetate were still alive.
• Skeletal related event: Here, the studies suggest that abiraterone acetate has an advantage when compared to the standard treatments. Things like bone fractures were less common with abiraterone acetate.
• Pain: In terms of this side effect, one of the studies suggests that abiraterone acetate has an advantage: An increase in pain was less common with abiraterone acetate than with the standard treatment.
• Health-related quality of life: The study suggests that there is an advantage here too. It took 13 months before half of the men who had treatment with abiraterone acetate experienced a decrease in quality of life, and only 8 months for this to happen in half of the men who had the standard treatment.

What are the disadvantages of abiraterone acetate?

• Serious side effects: The study suggests that abiraterone acetate has a disadvantage here. Half of the men who had treatment with abiraterone acetate already had serious side effects within the first 14 months, while it took 20 months for the same to happen in half of the men who had the standard treatment.

No difference

No noticeable difference was found in terms of:

• General health
• Exhaustion
• Pain or exhaustion affecting day-to-day activities
• Local prostate problems
• Treatment stopped due to side effects
• Fluid retention (edema)

What remains unanswered?

• The manufacturer didn't provide any suitable data about side effects like heart failure or ischemic heart disease.

This information summarizes the main results of a review produced by the Institute for Quality and Efficiency in Health Care (IQWiG, Germany). The review was commissioned by the German Federal Joint Committee (G-BA) as part of the “early benefit assessment of medications.” On the basis of this review and the hearings received, G-BA passed a resolution on the added benefit of abiraterone acetate (Zytiga).