CHICAGO ― Long-term therapy with abiraterone acetate plus prednisone (AA+P) in patients diagnosed with asymptomatic and mildly symptomatic metastatic castration-resistant prostate cancer (mCRPC) who have not undergone prior chemotherapy is safe and associated with prolonged progression-free survival (PFS), according to a post-hoc long-term safety and tolerability analysis reported at the 2013 American Society of Clinical Oncology (ASCO) Annual Meeting.
The analysis “confirms the delay in progression and prolongation of life with a favorable safety profile” in patients treated with AA+P for 24 months or longer, reported lead author Dana E. Rathkopf, MD, from Memorial Sloan-Kettering Cancer Center in New York, NY, and coauthors.
AA is a CYP17 inhibitor, found by the coauthors to prolong survival with a favorable safety profile among men diagnosed with progressive, metastatic castration-resistant prostate cancer (mCRPC).
A total of 1,088 patients were randomly assigned 1:1 to receive oral prednisone 5 mg twice daily with either placebo or AA 1,000 mg. The post-hoc analysis assessed safety and tolerability of treatment.
At a median prespecified interim analysis follow-up of 27.1 months, radiographically determined PFS (rPFS) and overall survival (OS) were improved among patients in the AA arm versus placebo (rPFS: hazard ratio [HR], 0.52; 95% CI: 0.45-0.61; P<0.0001; OS: HR, 0.79; 95% CI: 066.-0.96; P=0.0151), the coauthors reported.
However, OS did not achieve the prespecified efficacy boundary of P=0.0035, they cautioned.
“The percent incidence of grade 3/4 AEs was low despite longer exposure with abiraterone,” the authors noted. “No new safety signals were observed with 24 months or longer exposure with abiraterone plus prednisone or with prednisone alone.”