Division of Hematology /Oncology, University of California - San Francisco, California.
Abiraterone is an oral inhibitor of CYP17, essential for androgen biosynthesis. This multicenter study assessed its efficacy in patients with CRPC without prior chemotherapy or CYP17 targeted therapy, and assessed frequency of bone scans discordant with PSA and clinical response.
33 patients received abiraterone acetate 1,000 mg daily with prednisone 5 mg twice daily in continuous 28-day cycles. Patients were evaluated monthly for efficacy and safety. Bone scan flare was defined as the combination, after 3 months of therapy, of an interpreting radiologist's report indicating "disease progression" in context of a ≥50% decline in PSA, with scan improvement or stability 3 months later.
A ≥50% PSA decline at week 12 was confirmed in 22/33 (67%) patients. PSA declines of ≥50% were seen in 26/33 (79%) patients. Undetectable PSA levels (≤ 0.1 ng/mL) occurred in two patients. Median time on therapy and time to PSA progression were 63 weeks and 16.3 months, respectively. Twenty-three patients were evaluable for bone scan flare. Progression was indicated in radiologist's report in 12/23 (52%), and 11/12 subsequently showed improvement or stability. As prospectively defined, bone scan flare was observed in 11/23 (48%) evaluable patients or 11/33 (33%) enrolled patients. Adverse events were typically grade 1/2 and consistent with prior published abiraterone reports.
Clinical responses to abiraterone plus prednisone were frequent and durable in men with metastatic CRPC. Further investigation is needed to clarify the confounding effect of bone scan flare on patient management and interpretation of results.
Ryan CJ, Shah SK, Efstathiou E, Smith MR, Taplin ME, Bubley GJ, Logothetis CJ, Kheoh T, Kilian C, Haqq C, Molina A, Small EJ. Are you the author?
Reference: Clin Cancer Res. 2011 Jun 1. Epub ahead of print.