WASHINGTON, DC USA (UroToday.com) - May 16, 2011 - Abiraterone acetate (AA) with low-dose prednisone (P) extended overall survival with favorable PSA and radiographic responses in patients with castration-resistant prostate cancer progressing after docetaxel-based chemotherapy, according to updated data from COU-AA-301, a multi-institutional, randomized, double-blind, placebo-controlled, phase III study from researchers at 147 institutions across 13 countries.
AA is a selective androgen biosynthesis inhibitor that blocks the action of the CYP17 gene, which plays a vital role in androgen and estrogen biosynthesis.
Data will be presented to the media during a special press conference on Monday, May 16, 2011 at 10:00 a.m. at the Walter E. Washington Convention Center in Washington, DC, during the 2011 Annual Meeting of the American Urological Association (AUA). The session will be moderated by Christopher Amling, MD.
The study included 1,195 patients with castration-resistant prostate cancer who had previously undergone chemotherapy with docetaxel. Patients were randomized 2:1 to receive 1,000 mg AA plus 5 mg P twice daily, or placebo. Patients were assessed using prostate-specific antigen (PSA) scores and radiographic tests.
The study, of which the primary endpoint was overall survival, demonstrated:
- An increase in overall survival by a median of 14.8 months, compared to 10.9 with placebo.
- An improved time to PSA progression of 10.2 months
- That AA+P reduced the risk of death by 35 percent (HR=0.65) compared with placebo.
AA+P demonstrated a favorable safety profile compared to placebo, with patients experiencing less fatigue (8 percent vs. 10 percent), back pain (6 percent vs. 10 percent) and spinal cord compression (3 percent vs. 5 percent). The most common grade 3/4 adverse events were decreased lymphocyte levels (21 percent vs. 23 percent), fluid retention (2.3 percent vs. 1 percent), hypokalemia (3.9 percent vs. 0.8 percent), liver function test abnormalities (3.5 percent vs. 3.0 percent), hypertension (1.3 percent vs. 0.3 percent) and cardiac disorders (4.1 percent vs. 2.3 percent).
“In men with metastatic prostate cancer, hormone therapy typically slows disease progression for a substantial time. Chemotherapy becomes an option when the disease no longer responds to standard hormone therapy,” Dr. Amling said. “But what happens when prostate cancer progresses after chemotherapy? By targeting persistent androgen synthesis, these data suggest that abiraterone, combined with low-dose prednisone, may be an option.”