Abiraterone acetate increased survival in metastatic castration-resistant prostate cancer

ESMO 35th Congress

MILAN — Patients treated with abiraterone acetate for metastatic castration-resistant prostate cancer that progressed after chemotherapy had a 4-month increase in median survival when compared with patients assigned placebo. Johann de Bono, PhD, of the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, presented the phase 3 data during a press conference held here.

“This is the fifth drug in the history of prostate cancer medicine. It is very well tolerated, everyone benefited from the drug, no matter their age,” de Bono said.

Researchers hypothesized that targeting persistent androgen synthesis and androgen receptor signaling with abiraterone acetate would improve OS in 1,195 patients previously treated with a docetaxel chemotherapy regimen across 147 centers in 13 countries. Primary endpoint was OS; secondary endpoints were time to prostate-specific androgen progression, radiographic PFS and prostate-specific androgen response rate.

Median overall survival was 10.9 months for 398 patients assigned corticosteroid prednisone plus placebo compared with 14.8 months for 797 patients assigned abiraterone acetate plus prednisone (HR=0.65; 95% CI, 0.54-0.77).

In addition, researchers observed significant differences in time to prostate-specific antigen progression, radiographic PFS, and persistent androgen synthesis response rate. More adverse events were observed with abiraterone acetate than with placebo, including fluid retention (30.5% vs. 22.3%); hypokalemia (17.1% vs. 8.4%); grade ¾ hypertension (1.3% vs. 0.3%); and cardiac events (12.5% vs. 9.4%), respectively.

During an interim analysis of the study, de Bono said the beneficial effect of abiraterone led the trial’s Independent Data Monitoring Committee to recommend unblinding the trial, so patients on the placebo arm could take abiraterone acetate. “Once we knew that the drug could prolong life for many patients, it was ethically critical that we made it available to all patients on the trial,” he said in a press release.

The results of this study show that [abiraterone ] adds to the range of treatment options available for patients with advanced disease, with limited toxicity. These results also challenge the current idea that there is no further treatment after chemotherapy for these patients. In fact, timing of hormone therapy and chemotherapy will become more complex and important in the future management of castration-resistant prostate cancer.

– Carsten Bokemeyer, MD
Professor and director of University Cancer Center Hamburg, Germany

For more information:

DeBono J. #LBA5. Presented at: the ESMO 35th Congress; Oct. 8-12, 2010; Milan, Italy.

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