Fulvestrant Versus Fulvestrant Plus Palbociclib in Operable Breast Cancer Responding to Fulvestrant

This is a multicenter, international, double-blind, randomized study. Eligible patients based on inclusion/exclusion criteria will be assessed using OncotypeDX molecular test. Patients with low/intermediate risk (Recurrence Score \<31) will be treated with the induction neoadjuvant Fulvestrant (500 mg (milligram) intra muscular(i.m) at Day 1, 14 and 28 and then every 4 weeks), plus Goserelin (3.6 mg subcutaneous (s.c) every 4 weeks, only for pre and peri-menopausal patients) for 4 months, followed by clinical and radiological assessment of the disease response. Patients with objective response or stabilization will be randomized and treated for 4 additional months with: * Fulvestrant 500 mg i.m every 4 weeks (+ Goserelin 3.6 mg s.c every 4 weeks, only for pre and peri-menopausal patients) and Placebo or * Combination Fulvestrant 500 mg i.m every 4 weeks (+ Goserelin 3.6 mg s.c every 4 weeks, only for pre and peri-menopausal patients) and Palbociclib 125 mg per os daily, 3 weeks on and 1 week off. Patients with documented progressive disease will be considered at the discretion of the investigator for surgery or neoadjuvant chemotherapy. The preferred chemotherapy protocol will be FEC 100 -Taxotere (5fluorouracil 500mg/m2, Epirubicin 100 mg/m2, cyclophosphamide 500 mg/m2 (FEC) q3 weeks for 3 cycles followed by Docetaxel 100 mg/m2 (T) q 3 weeks for 3 cycles) for a total of 6 cycles with clinical and radiological assessment after each 3 cycles of chemotherapy (CT). Chemotherapy candidates will as well undergo surgery. The expected interval between the cycles will be 21 days, unless the patient has not recovered from toxicity. Specific dose adjustments will be set out in the protocol. Breast and nodal surgery will be performed at completion of therapy (8 months of hormonal therapy for responding patients and 6 additional cycles of CT for non-responders). The type of surgery will be left at the discretion of the investigators. Radiation therapy and adjuvant systemic treatment and endocrine therapy will be as well left at the discretion of the investigators. Patients will be followed every 6 months during 5 years post surgery.