Second-line abiraterone improved OS, reduced risk for death in prostate cancer

de Bono J. N Engl J Med. 2011;364:1995-2005.

At median follow-up of nearly 13 months, OS was 4 months longer in patients with metastatic castration-resistant prostate cancer who were assigned to abiraterone vs. those assigned to placebo and prednisone.

Results of a study involving 1,195 men also showed that abiraterone (Zytiga, Centocor Ortho BioTech), an inhibitor of androgen biosynthesis, was also superior for PSA response rate, time to PSA progression and median PFS.

The FDA approved abiraterone for use in patients with metastatic castration-resistant prostate cancer in April.

From May 2008 to June 2009, patients were enrolled in this phase 3, multinational, randomized, double blind, placebo-controlled study conducted at 147 sites in 13 countries. All had undergone at least one round of docetaxel-based chemotherapy.

Patients were randomly assigned to 5 mg of twice-daily prednisone with either 1,000 mg of abiraterone (n=797) or placebo (n=398).

There were 333 deaths (42%) in the abiraterone group vs. 219 (55%) in the placebo group. Patients assigned to abiraterone had a median OS of 14.8 months vs. 10.9 months for placebo on multivariate analysis (HR=0.66; 95% CI, 0.55-0.78). There was a 35.4% reduced risk for death associated with abiraterone.

All secondary endpoints demonstrated the superiority of abiraterone acetate over placebo, including confirmed PSA response rate (29% vs. 6%), objective response rate (14% vs. 3%), time to PSA progression (10.2 months vs. 6.6 months) and median PFS (5.6 vs. 3.6 months). Abiraterone was associated with a 42% reduction in the risk for disease progression (HR=0.58; 95% CI, 0.46-0.73) according to PSA concentration. Abiraterone was associated with a 33% reduction in the risk of progression based on radiographic imaging (HR=0.67; 95% CI, 0.58-0.78).

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