Arm B: Patients receive the same endocrine treatment as in arm A together with palbociclib 125 mg orally days 1-21, followed by a 7-days rest period. The combined treatment is continued for further 12 weeks, if re-evaluation after 6 weeks, week 10 of the preoperative treatment, does not indicate progression. Upon progression (PD), individualized management, preferentially surgery, is the primary option.