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Abiraterone acetate significantly improved survival in patients with advanced prostate cancer
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The addition of abiraterone acetate to prednisone conferred significant improvements in OS in patients with metastatic castration-resistant prostate cancer, according to phase 3 study results.
Abiraterone acetate (Zytiga, Janssen Biotech) is a selective inhibitor that blocks CYP17, an enzyme involved in the production of testosterone. Blocking production of this enzyme could reduce prostate cancer progression, according to background information in the study.
Karim Fizazi, MD, PhD, a medical oncologist in the department of cancer medicine at the Institut Gustave Roussy at the University of Paris, and colleagues enrolled 1,195 patients with metastatic castration-resistant prostate cancer that progressed after docetaxel chemotherapy.
The researchers conducted the multinational, double blind study at 147 sites in 13 countries from May 8, 2008, to July 28, 2009.
The researchers assigned 797 patients to prednisone 5 mg twice daily, plus abiraterone acetate 1,000 mg once daily. The other 398 patients received prednisone plus placebo.
OS served as the primary endpoint.
After a median follow-up of 20.2 months, 775 death events occurred.
Researchers reported significantly longer median OS among patients in the abiraterone group (15.8 months vs. 11.2 months; HR=0.74; 95% CI, 0.64-0.86).
Study results showed the addition of abiraterone also improved other efficacy endpoints, including median time to PSA progression (8.5 months vs. 6.6 months; HR=0.63; 95% CI, 0.52-0.78) and radiographic PFS (5.6 months vs. 3.6 months; HR=0.66; 95% CI, 0.58-0.76).
The rate of PSA response and objective response also was higher in the abiraterone group (29.5% vs. 5.5%).
The percentage of patients who experienced grade-3 or -4 adverse events was similar in both treatment groups, the researchers said.
A higher proportion of mineralocorticoid, fluid retention and/or adema-related adverse events were observed in the abiraterone group, a finding that Fizazi and colleagues said was expected.
The researchers said 105 patients (13%) in the abiraterone group discontinued treatment due to adverse events compared with 71 (18%) in the placebo group.
“Our work confirms that abiraterone acetate can be used as an effective and safe treatment for castration-resistant metastatic prostate cancer patients whose disease continues to progress after docetaxel treatment,” Fizazi said in a press release. “Furthermore, unlike current alternatives for this patient population, abiraterone plus prednisone therapy can be given orally in an outpatient setting, providing an additional benefit for both patients and clinicians.”
In an accompanying editorial, Guru Sonpavde, MD, director of urologic medical oncology at the University of Alabama, Birmingham, called the findings “an important advance” in the therapy of metastatic castration-resistant prostate cancer.
“Further clinical trials investigating novel drugs and combinations should be strongly encouraged since all available options are palliative by nature,” Sonpavde wrote.
Disclosure: The researchers report serving on advisory boards for, receiving lecture fees from and holding employment relationships with Amgen, GlaxoSmithKline, Janssen Research and Development, Janssen-Cilag, Johnson & Johnson, Novartis, Sanofi-Aventis and other pharmaceutical companies.
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