Neoadjuvant Biomarker ResearcH Study of Palbociclib Combined With Endocrine Therapy in Estrogen Receptor Positive/HER2 Negative Breast CAncer (NeoRHEA)

This is an open-label, single arm, phase 2 trial that will include pre or post-menopausal female subjects, that have ER-positive, HER2-negative early breast cancer. Subject will receive 4 cycles of palbociclib 125 mg (each cycle of palbociclib consists of treatment from D1 to D21 followed by a week of rest) combined with endocrine therapy given continuously (each cycle of endocrine therapy consists of treatment from D1 to D28). The endocrine therapy will be determined according to the menopausal status of the subject evaluated at the study screening.