• Women and Men; ≥18 years at the time of screening (or per national guidelines)

• Histologically confirmed ER+/HER2- early-stage resected invasive breast cancer with absence of any evidence of metastatic disease as defined in the protocol.

• Completed adequate (definitive) locoregional therapy (surgery with or without radiotherapy) for the primary breast tumour(s), with or without (neo)adjuvant chemotherapy.

• Patients must be randomised within 12 months of definitive breast surgery.

• Patients may have received up to 12 weeks of endocrine therapy prior to randomisation.

• Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1

• Adequate organ and bone marrow function