The purpose of this study is to evaluate anti-cancer stem cell (CSC) activity (measured by the amount of Aldehyde dehydrogenase 1/ALDH1+ cells before and after treatment) of pre-operative bevacizumab in combination with conventional chemotherapy in breast cancer receiving neo-adjuvant treatment, compared to a control arm receiving chemotherapy alone.

Inclusion Criteria:

• Women older than 18 ys
• Primary breast cancer treated in the neoadjuvant setting (synchronous metastatic disease are eligible)
• Primary breast tumor accessible to initial biopsy
• White Blood Count > 3.000/µl and Absolute neutrophil count ≥ 1.500/µl AND platelets ≥ 100 x 109/L AND Hemoglobin ≥ 9 g/dL, Serum creatinine ≤ 150µm/l• Urine dipstick for proteinuria < 2+. Patients discovered to have ≥ 2+ proteinuria on dipstick urinalysis at baseline should undergo a 24 hour urine collection and must demonstrate ≤ 1 g of protein in 24 hours, Total bilirubin ≤ 1.5 ULN and ASAT < 2.5 ULN AND ALAT < 1.5 ULN (2.5 if liver metastasis), Adequate coagulation function: International normalized ratio (INR) ≤ 1.5 and TCA ≤ 1.5 x ULN
• Left ventricular ejection fraction (LVEF) ≥ 55% (isotopic or
• ultrasound methods)
• Karnofsky Index > 1 ; Performance status 0 to 1
• Patients must have signed a written informed consent form prior to any study specific screening procedures
• Patient affiliated to the national "Social Security" regimen or beneficiary of this regimen.

Exclusion Criteria:

• Previous history of cancer (other than curatively treated basal and squamous cell carcinoma of the skin and/or in-situ carcinoma of the cervix) relapsing within the 5 years before study entry
• Known contra-indication to anticancer compounds used
• Uncontrolled hypertension (systolic >150 mmHg and/or diastolic >100 mmHg) or history of hypertensive encephalopathy
• History of inherited diathesis or recent thrombotic events
• Non-healing wound, active peptic ulcer or bone fracture.
• Major surgery or significant traumatic injury within 28 days prior to study treatment start
• History of abdominal fistula, trachea-oesophageal fistula or urinary fistula
• Use of Non Steroid Anti Inflammatory or full dose anticoagulants or antiaggregation treatments within 10 days
• Pregnancy and breast feeding, premenopausal patient and no effective contraception
• Brain metastasis.
• Any unstable severe disease such as : uncontrolled cardiac or vascular disease, uncontrolled hemorrhagy, uncontrolled neuropsychiatric disorders, including dementia, uncontrolled infection or any severe disorders that may preclude study participation
• Patient considered geographically, socially or psychologically unable to comply with the treatment and the required medical follow-up.