Benefits of abiraterone acetate consistent across subgroups

May 1, 2011

The survival benefits of abiraterone acetate remained consistent across a wide range of subgroups of men with castration-resistant prostate cancer that had progressed on docetaxel (Taxotere).

Orlando, FL-The survival benefits of abiraterone acetate remained consistent across a wide range of subgroups of men with castration-resistant prostate cancer that had progressed on docetaxel (Taxotere), according to a new analysis of a large randomized trial.

"Abiraterone is a new treatment option that prolongs survival in men with castration-resistant prostate cancers that have been previously treated with chemotherapy," said Dr. Scher, chief of genitourinary oncology at Memorial Sloan-Kettering Cancer Center in New York. "Considering castration-resistant prostate cancer as 'hormone refractory' may deny these patients safe and life-prolonging treatment."

Dr. Scher presented results of an analysis to determine whether certain types of patients benefited more or less from treatment with abiraterone. The trial involved 1,200 men with castration-resistant prostate cancer that had progressed on one or two prior chemotherapy regimens, which had to include docetaxel.

The 4-month difference in overall survival translated into a 35% reduction in the hazard ratio (p<.0001). The trial design included a prespecified subgroup analysis of clinically relevant subgroups.

The subgroup analysis affirmed the survival benefit with abiraterone shown in the overall results versus placebo, including those patients:

Patients with ECOG performance status 2 had a slight improvement in survival with abiraterone, but the difference did not achieve statistical significance (7.3 vs. 7.0 months).

Significantly more patients treated with abiraterone had objective responses, whether investigator assessed (38% vs 10.1%, p<.0001) or confirmed (29% vs 5.5%, p<.0001).

Abiraterone had a safety profile no different from that of placebo. In fact, the frequency of severe adverse events, events leading to discontinuation, and fatal events was lower in the abiraterone group.

Retention, hypokalemia among AEs

The most common adverse events among abiraterone-treated patients were fluid retention (31%), hypokalemia (17%), cardiac disorders (13%, primarily tachycardia and atrial fibrillation), and hypertension and abnormal liver function tests (10% each). Grade 3-4 events were uncommon.

"Abiraterone acetate prolongs overall survival in patients with metastatic castration-resistant prostate cancer who have progressed after docetaxel-based chemotherapy," Dr. Scher said in conclusion. "The favorable effect on overall survival was observed across multiple patient subgroups. A significant improvement in time to PSA progression, radiographic progression-free survival, and PSA response rate also was observed in patients treated with abiraterone acetate."

Dr. Scher disclosed relationships with Cougar Pharmaceuticals and Johnson & Johnson.