Prostate cancer
STAMPEDE Trial: Adding Abiraterone to Standard Treatment Improves Survival in Advanced Prostate Cancer

Nick James, University of Birmingham, UK, presented the latest data at the 2017 ASCO Annual Meeting (Abstract LBA5003).

The STAMPEDE clinical trial of nearly 2,000 men shows that adding abiraterone acetate (Zytiga) to a standard initial treatment regimen for high-risk, advanced prostate cancer lowers the relative risk of death by 37%. The 3-year survival rate was 76% with standard therapy alone vs 83% with standard therapy plus abiraterone.

About the Study

STAMPEDE is an ongoing multiarm, multistage randomized clinical trial conducted in the United Kingdom and Switzerland. The current analysis compared standard therapy with standard therapy plus abiraterone in men with high-risk prostate cancer who were starting androgen-deprivation therapy. The men had either locally advanced or metastatic cancer, and all were commencing long-term standard androgen-deprivation therapy for the first time. The standard therapy consisted of androgen-deprivation therapy for at least 2 years; men with locally advanced cancer (48% of all patients) could also receive radiation therapy in addition to androgen-deprivation therapy. A novel approach to the clinical trial design meant this comparison recruited patients much more quickly than most academic-led trials, and STAMPEDE will report randomized data from at least 10 comparisons over 2 decades.

Key Findings

• At a median follow-up of 40 months, 262 deaths had occurred in the standard therapy group and 184 deaths had occurred in the abiraterone group.
• The 3-year overall survival rate was 83% in the abiraterone group vs 76% in the standard therapy group.
• Abiraterone lowered the relative chance of treatment failure (measured by worsening scans or symptoms, or elevated prostate-specific antigen level) by 71% compared with standard therapy. The effects were consistent across the different subgroups of people enrolled in the trial.

Overall, side effects were similar between the two groups. Severe side effects were more common in the abiraterone group, occurring in 41% of patients compared with 29% of patients in the standard therapy group. The main side effects occurring more frequently with abiraterone were cardiovascular problems such as high blood pressure; there were also more liver problems with abiraterone. There were two treatment-related deaths in the abiraterone group and one in the standard therapy group.