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)

Ann Oncol. 2016 May;27(5):812-8. doi: 10.1093/annonc/mdw067. Epub 2016 Feb 18.


Background: Several expression array studies identified molecular apocrine breast cancer (BC) as a subtype that expresses androgen receptor (AR) but not estrogen receptor α. We carried out a multicentre single-arm phase II trial in women with AR-positive, estrogen, progesterone receptor and HER2-negative (triple-negative) metastatic or inoperable locally advanced BC to assess the efficacy and safety of abiraterone acetate (AA) plus prednisone.

Patients and methods: Patients with a metastatic or locally advanced, centrally reviewed, triple-negative and AR-positive (≥10% by immunohistochemistry, IHC) BC were eligible. Any number of previous lines of chemotherapy was allowed. AA (1000 mg) was administered once a day with prednisone (5 mg) twice a day until disease progression or intolerance. The primary end point was clinical benefit rate (CBR) at 6 months defined as the proportion of patients presenting a complete response (CR), partial response (PR) or stable disease (SD) ≥6 months. Secondary end points were objective response rate (ORR), progression-free survival (PFS) and safety.

Results: One hundred and forty-six patients from 27 centres consented for IHC central review. Of the 138 patients with sufficient tissue available, 53 (37.6%) were AR-positive and triple-negative, and 34 of them were included from July 2013 to December 2014. Thirty patients were eligible and evaluable for the primary end point. The 6-month CBR was 20.0% [95% confidence interval (CI) 7.7%-38.6%], including 1 CR and 5 SD ≥6 months, 5 of them still being under treatment at the time of analysis (6.4+, 9.2+, 14.5+, 17.6+, 23.4+ months). The ORR was 6.7% (95% CI 0.8%-22.1%). The median PFS was 2.8 months (95% CI 1.7%-5.4%). Fatigue, hypertension, hypokalaemia and nausea were the most common drug-related adverse events; the majority of them being grade 1 or 2.

Conclusions: AA plus prednisone treatment is beneficial for some patients with molecular apocrine tumours and five patients are still on treatment.

Clinicaltrialsgov: NCT01842321.

Keywords: abiraterone acetate; androgen receptor; breast cancer; molecular apocrine; triple-negative.

Publication types

  • Clinical Trial, Phase II
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abiraterone Acetate / administration & dosage*
  • Aged
  • Aged, 80 and over
  • Antineoplastic Combined Chemotherapy Protocols / administration & dosage*
  • Disease-Free Survival
  • Drug-Related Side Effects and Adverse Reactions / classification
  • Drug-Related Side Effects and Adverse Reactions / pathology
  • Female
  • Humans
  • Kaplan-Meier Estimate
  • Middle Aged
  • Prednisone / administration & dosage*
  • Receptor, ErbB-2 / genetics
  • Receptors, Androgen / genetics
  • Receptors, Progesterone / genetics
  • Treatment Outcome
  • Triple Negative Breast Neoplasms / drug therapy*
  • Triple Negative Breast Neoplasms / genetics
  • Triple Negative Breast Neoplasms / pathology


  • AR protein, human
  • Receptors, Androgen
  • Receptors, Progesterone
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • Abiraterone Acetate
  • Prednisone

Associated data

  • ClinicalTrials.gov/NCT01842321