Dr. Charles J. Ryan of the University of California, San Francisco's Helen Diller Family Comprehensive Cancer Center said the interim analyses of the randomized, placebo-controlled Phase 3 study, showed those who took abiraterone acetate -- zytiga -- plus prednisone showed a statistically significant improvement compared with patients treated with placebo plus prednisone.
"These results are very promising for abiraterone acetate in the treatment of patients with metastatic castration-resistant prostate cancer who are asymptomatic or mildly symptomatic and have not received chemotherapy," Ryan, the lead investigator, said in a statement. "This is an important study with all clinically relevant endpoints favoring treatment with abiraterone acetate plus prednisone, and is also the first to suggest that inhibiting androgen production -- hormones -- significantly delays initiation of cytotoxic chemotherapy."
Patients in the zytiga arm of the study experienced more grade 3 and grade 4 adverse events than those in the control arm, including cardiac disorders -- 6 percent versus 3 percent and hypertension -- 4 percent versus 3 percent. Fatigue was the most common adverse event observed in the study, Ryan said.
The results were presented at the 48th annual meeting of the American Society of Clinical Oncology in Chicago.