Tailoring NEOadjuvant Therapy in Hormone Receptor Positive, HER2 Negative, Luminal Breast Cancer.

Inclusion Criteria: * Postmenopausal women presenting with histological proven (core biopsy material) hormone receptor positive (ER≥50%, PR any), HER2 negative, stage II/ III breast cancer. * Measurable disease (breast and/or lymph nodes) * WHO 0-2 * Adequate bone marrow function (within 4 weeks prior to registration): WBC≥3.0x109/l, neutrophils ≥1.5 x 109/l, platelets ≥100 x 109/l * Adequate liver function (within 4 weeks prior to registration): bilirubin ≤1.5 x upper limit of normal (UNL) range, ALAT and/or ASAT ≤2.5 x UNL, Alkaline Phosphatase ≤5 x UNL * Adequate renal function (within 4 weeks prior to registration): the calculated creatinine clearance should be ≥50 ml/min * Accessible for treatment and follow-up * Written informed consent Inclusion criteria randomization specific: In order to be eligible to be randomized in this study, a subject must meet all of the following criteria: * Registration in the NEOLBC trial before 2 weeks biopsy * Use of letrozole * Outcome central Ki67 determination in two weeks biopsy available. Exclusion Criteria: * Evidence of distant metastases (M1) * Previous invasive breast cancer * Prior chemotherapy, radiation therapy or hormonal therapy with the exception of patients who received letrozole ≤ 14 days (+ max. 4 days) prior to registration and who are still on letrozole. * Previous malignancy within 5 years, with exception of a history of a previous basal cell carcinoma of the skin or pre-invasive carcinoma of the cervix. * Peripheral neuropathy \> grade 2, whatever the cause * Serious other diseases as infections (hepatitis B, C and HIV), recent myocardial infarction, clinical signs of cardiac failure or clinically significant arrhythmias or on screening, any of the following cardiac parameters: bradycardia (heart rate \<50 at rest) or QTcF ≥450 msec. * Known hypersensitivity reaction to any of the components of the treatment (peanuts, soy) * Currently receiving warfarin or other coumarin derived anti-coagulant, for treatment, prophylaxis or otherwise. Therapy with heparin, low molecular weight heparin (LMWH), or fondaparinux is allowed. * Currently receiving any of the following substances and cannot be discontinued 7 days prior to randomisation: * Known strong inducers or inhibitors of CYP3A4/5, including grapefruit, grapefruit hybrids, pummelo's, star-fruit, pomegranate and Seville oranges. * That have a known risk to prolong the QT interval or induce Torsades de Pointes. * That have a narrow therapeutic window and are predominantly metabolized through CYP3A4/5. * Herbal preparations/medications, dietary supplements. * Medical or psychological condition which in the opinion of the investigator would not permit the patient to complete the study or sign meaningful informed consent.