Abiraterone Acetate/Prednisone in Metastatic Castration-Resistant Prostate Cancer: Final Analysis of Early-Access Protocol Study
Abiraterone acetate (Zytiga) is approved for use in combination with prednisone in the treatment of metastatic castration-resistant prostate cancer. As reported by Sternberg et al in The Lancet Oncology, results of an open-label, early-access protocol trial initiated prior to approval indicated no new safety signals with abiraterone acetate plus prednisone given after progression on chemotherapy.
Study Details
The study, conducted in 23 countries, included 2,314 patients with metastatic castration-resistant prostate cancer progressing after taxane chemotherapy enrolled between November 2010 and September 2013. Patients received abiraterone acetate 1,000 mg/day and prednisone 5 mg twice a day in 28-day cycles until disease progression, development of sustained side effects, or approval and availability of abiraterone acetate in the country of residence.
Adverse Event Profile
Median follow-up was 5.7 months. In total, 952 patients (41%) had a treatment-related grade 3 (36%) or 4 (5%) adverse event. The most common adverse events were hepatotoxicity (8%), hypertension (4%), cardiac disorders (2%), osteoporosis (1%), hypokalemia (1%), and fluid retention/edema (1%). Grade 3 (22%) or 4 (4%) serious adverse events were reported in 25% of patients; those reported in ≥ 1% of patients were back pain (2%), anemia (2%), pneumonia (1%), urinary tract infection (1%), hematuria (1%), and spinal cord compression (1%).
Adverse events led to discontinuation of treatment in 7% of patients, with 3% discontinuing due treatment-related adverse events. Death occurred in 7% of patients, with causes consisting of disease progression (4%), unrelated adverse event (3%), unknown reasons (1%), and drug-related adverse event (< 1%).
Median time to prostate-specific antigen progression was 8.5 months (95% confidence interval [CI] = 8.3–9.7 months) and median time to clinical progression was 12.7 months (95% CI = 11.8–13.8 months).
The investigators concluded: “No new safety signals or unexpected adverse events were found in this early-access protocol trial to assess abiraterone acetate for patients with metastatic castration-resistant prostate cancer who progressed after chemotherapy. Future work is needed to ascertain the most effective regimen of abiraterone acetate to optimise patients’ outcomes.”
Cora N. Sternberg, MD, of San Camillo Forlanini Hospital, Rome, is the corresponding author for The Lancet Oncology article.
The study was funded by Janssen Research & Development. For full disclosures of the study authors, visit www.thelancet.com.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
