Locoregional Treatment and Palbociclib in de Novo, Treatment Naive, Stage IV ER+, HER2- Breast Cancer Patients

Inclusion Criteria

• •1. Women with newly diagnosed and histologically proven de novo adenocarcinoma of the breast, Any T, any N, with at least one metastatic site measurable and/or non-measurable according to Response Evaluation Criteria In Solid Tumours (RECIST) v1.1 and/or PET Response Criteria in Solid Tumours (PERCIST) v1.0 and/or MD Anderson bone response criteria (MDA criteria). For patients with only bone metastases, at least one lytic and non-irradiated lesion must be present NB: Bilateral breast cancer is allowed only if tumours present similar histological criteria (morphological subtype, ER and HER2 status).
• •2. Estrogen Receptor (ER)-positive and HER2-negative breast cancer. To be considered as ER-positive, the biopsy of the primary tumour must display at least 10% of cancer cells with positive ER staining. HER2-positive is defined as IHC3+ or FISH/CISH amplified according to 2018 criteria
• •3. Age ≥18 years
• •4. Eastern Cooperative Oncology Group (ECOG) ≤2
• •5. Indication for treatment with palbociclib and letrozole (with or without ovarian suppression)
• •6. Diagnostic FFPE tumour sample and/or frozen primary breast tumour sample available
• •7. Women of childbearing potential must have a negative serum or urine pregnancy test done within 14 days before inclusion
• •8. Patients must agree to use adequate contraception methods for the duration of the study and for within 21 days after completing treatment
• •9. Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and any protocol-related procedures including absence of co-morbidities preventing surgery and or radiotherapy and 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
• •10. Patient affiliated to a social security system
• •11. Written informed consent obtained prior to performing any protocol-related procedures including screening evaluations