Abiraterone Acetate in Molecular Apocrine Breast Cancer

Inclusion Criteria: * Women aged ≥18 years; * Histologically confirmed locally advanced or metastatic breast cancer; * Triple negative breast cancer: Estrogen receptor (ER)-negative and Progesterone receptor (PR)-negative, as defined by a \<10 % tumour stained cells by immunohistochemistry (IHC); HER2 negative status (i.e. IHC score 0 or 1+, or IHC score 2+ and FISH/SISH/CISH negative), confirmed centrally before inclusion with FFPE tissue from either primary or metastatic breast cancer site\*; * Androgen receptor (AR)-positive, as defined centrally by a ≥10% tumour stained cells by IHC (AR assessment by local pathologist before inclusion is not mandatory); * Patients could be chemotherapy naïve (provided they are not presenting with life-threatening metastasis) or have received any number of previous lines of chemotherapy (providing their life expectancy is ≥3 months); * Pre and post menopausal patients are eligible. * Measurable or non measurable disease according to RECIST v1.1 criteria; * PS (ECOG) ≤2; * Normal haematological function: ANC ≥1,500/mm3; platelets count ≥100,000/mm3; haemoglobin \>10 g/dl; * Normal hepatic function: total bilirubin ≤1.5 upper normal limit (UNL); ASAT and ALAT ≤2.5 UNL (≤5 UNL in the presence of liver metastases); * Creatinine clearance (MDRD formula) ≥50 mL/min OR creatinine ≤1.5 times ULN; * Normal kalemia (serum potassium ≥3.5 mM), natremia and magnesemia; * Systolic blood pressure (BP) \<160 mm Hg and diastolic BP \<95 mm Hg, as documented on inclusion day (Hypertension at baseline assessment allowed provided it is currently controlled under anti-hypertensive drugs); * Cardiac ejection fraction ≥50% measured by MUGA or ECHO done within 4 weeks before inclusion; * If receiving a bisphosphonate or denosumab, dose must have been stable for at least 2 doses before inclusion; * Patient agreeing to use effective contraception during and for ≥ 6 months after completion of study treatment; * Patient able to comply with the protocol; * Patient must have signed a written informed consent form prior to any study specific procedures; * Patient must be affiliated to a Social Health Insurance. Exclusion Criteria: * Male breast cancer; * HER2-positive status (positivity defined as IHC3+ and/or FISH amplification \>2.2); * Other concurrent malignancies, except adequately treated cone-biopsied in situ carcinoma of the cervix or basal cell or squamous cell carcinoma of the skin; patients who have undergone potentially curative therapy for a prior malignancy are eligible provided there is no evidence of disease for ≥ 5 years and patient is deemed to be at low risk for recurrence; * Active brain metastases or leptomeningeal disease; History of brain metastases allowed provided lesions are stable for at least 3 months as documented by head CT scan or MRI of the brain; * Non-malignant systemic disease, including active infection or concurrent serious illness that would make the patient a high medical risk; * Significant cardiovascular disease, including any of the following: 1. NYHA class III-IV congestive heart failure; 2. Unstable angina pectoris or myocardial infarction within the past 6 months; 3. Severe valvular heart disease; 4. Ventricular arrhythmia requiring treatment. * Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not be included; * Patients with known allergies, hypersensitivity or intolerance to abiraterone acetate, prednisone, or their excipients; * Persistent toxicities ≥ grade 2 from any cause, except chemotherapy-induced alopecia and Grade 2 peripheral neuropathy; * Active or uncontrolled autoimmune disease requiring concurrent corticosteroid therapy; * Any gastrointestinal disorder interfering with absorption of the study drug; * Difficulties with swallowing study capsules; * Prior anticancer therapy, including radiotherapy, endocrine therapy, immunotherapy, chemotherapy (CT) within the last 3 weeks (2 weeks for oral or weekly CT ; 6 weeks for nitrosoureas and mitomycin C), or other investigational agents ; Concurrent palliative radiotherapy allowed; * Concurrent enrolment in another clinical trial in which investigational therapies are administered; * Pregnant women, women who are likely to become pregnant or are breast-feeding; * Patients with any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial; * Patients with history of non compliance to medical regimens or unwilling or unable to comply with the protocol; * Individual deprived of liberty or placed under the authority of a tutor.