Adjuvant Palbociclib in Elderly Patients With Breast Cancer

The primary objective of this trial is to assess the efficacy of the combination of at least 5 year endocrine therapy and 2 year-palbociclib as adjuvant systemic treatment instead of adjuvant chemotherapy followed by endocrine therapy in older patients with stage II-III ER+/HER2- early breast cancer. This is a two-arm open-label multi-center randomized (2:1) non-comparative phase II study in elderly patients with stage II/III, ER+, HER2- early breast cancer for whom treatment with chemotherapy is indicated. Patients will be randomized with a 2:1 allocation rate to the following treatment arm: * experimental palbociclib arm: Standard adjuvant endocrine therapy for a duration of at least 5 years + palbociclib for a total duration of up to 2 years. * control chemotherapy arm: adjuvant chemotherapy (4 cycles of docetaxel/doxorubicin/epirubicin-cyclophosphamide; or of weekly paclitaxel D1, D8, and D15 q3w if a 3 weekly schedule is not desired), followed by standard adjuvant endocrine therapy for a duration of at least 5 years. The primary endpoint of the study is the 3-year D-RFI rate in the experimental arm.