Abiraterone Acetate Plus Prednisone Beneficial for Some With AR-positive, Triple-negative Breast Cancer

Treatment with abiraterone acetate plus prednisone was beneficial for some patients with molecular apocrine breast cancer, a subtype that expresses androgen receptor (AR), but not estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2, a study published in the Annals of Oncology has shown.¹ 

In this phase 2 trial, investigators assessed the efficacy and safety of abiraterone acetate plus prednisone in women with AR-positive, triple-negative metastatic or inoperable locally advanced breast cancer.

A total of 146 patients were included, and 138 had enough available tissue for analysis. Of those, 53 (37.6%) had AR-positive triple-negative disease and 34 were included in the study from July 2013 to December 2014. Any number of previous treatments was allowed. Abiraterone acetate (1000 mg) was administered once daily with prednisone (5 mg) twice daily until disease progression or intolerance.

The primary endpoint was clinical benefit rate at 6 months, defined as patients having a complete response, partial response, or stable disease within 6 months. Secondary endpoints included objective response rate, progression-free survival, and safety.

Results showed that out of the 30 patients eligible for evaluation of the primary endpoint, 6-month clinical benefit rate was 20.0% (95% CI, 7.7 – 38.6). One patient had a complete response, and 5 patients had stable disease within 6 months. Five patients were still being treated at the time of analysis.

Overall response rate was 6.7% (95% CI, 0.8 – 22.1) and median progression-free survival was 2.8 months (95% CI, 1.7 – 5.4).

In regard to safety, the most common drug-related adverse events were fatigue, hypertension, hypokalemia, and nausea; most were grade 1/2 in severity.

Reference

1. Bonnefoi H, Grellety T, Tredan O, et al. A phase II trial of abiraterone acetate plus prednisone in patients with triple-negative androgen receptor positive locally advanced or metastatic breast cancer (UCBG 12-1) [published online ahead of print February 18, 2016]. Ann Oncol. doi: 10.1093/annonc/mdw067.