Study to Evaluate the Extended Overall Survival (OS) Data From PARSIFAL Study (The PARSIFAL-LONG Study)

Inclusion Criteria

• •1. Patients previously randomized in the PARSIFAL trial (N = 486).
• •2. Patients did not withdraw consent to participate in the PARSIFAL clinical trial.
• •1. Postmenopausal women, as defined by any of the following criteria:
• •* Age 60 or over
• •* Age 45 to 59 years and meets ≥1 of the following criteria: amenorrhea for ≥ 24 months or amenorrhea for \< 24 months and follicle-stimulating hormone within the postmenopausal range (including patients with hysterectomy, prior hormone replacement therapy or chemotherapy-induced amenorrhea).
• •* Over 18 years of age and bilateral oophorectomy
• •OR:
• •Premenopausal women provided they are being treated with LHRH analogues for at least 28 days prior to study entry.
• •2. Eastern Cooperative Oncology Group (ECOG) score lower or equal to 2.
• •3. Histologically confirmed recurrent ER-positive (oestrogen and/or progesterone) HER2-negative locally advanced or metastatic BC patients (Breast cancer that have at least 1% of cells staging positive for ER should be considered ER-positive according to National Comprehensive Cancer Network (NCCN) and American Society of Clinical Oncology (ASCO) guidelines.
• •4. Patients should not be candidates for a local treatment with a radical intention.
• •5. No prior hormonal or chemotherapy line in the metastatic setting.
• •6. Patient must have measurable (according to RECIST 1.1) or non-measurable disease with these exceptions:
• •3. Renal: serum creatinine \< 1.5 x ULN.
• •9. Exhibit patient compliance and geographic proximity that allow for adequate follow-up.
• •10. Patient has been informed about the nature of study, and has agreed to participate in the study, and signed the Informed Consent form prior to participation in any study-related activities.
• •11. No other malignancies within the past five years except adequate treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix.
• •12. Resolution of all acute toxic effects of prior anti- cancer therapy or surgical procedures to NCI- CTCAE version 4.0 Grade ≤ 1 (except alopecia or other toxicities not considered a safety risk for the patient at investigator's discretion).
• •13. Patient has been informed about the translational sub-study and has agreed to participate in the collection of blood and tumor tissue samples by signing the Informed Consent form.
• •13. Known hypersensitivity to letrozole, fulvestrant or any of their excipients, or to any palbociclib excipients.
• •14. Corrected QT Interval (QTc) \>480 msec on basal assessments, personal history of long or short QT syndrome, Brugada syndrome or known history of QTc prolongation, or Torsade de Pointes (TdP).
• •15. Uncontrolled electrolyte disorders that can compound the effects of a QTc-prolonging drug (e.g., hypocalcemia, hypokalemia, hypomagnesemia).