A Study of Camizestrant in ER+/HER2- Early Breast Cancer After at Least 2 Years of Standard Adjuvant Endocrine Therapy

Inclusion Criteria: * 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 high or intermediate risk of recurrence, based on clinical-pathological risk features, 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 * Completed at least 2 years but no more than 5 years (+3 months) of adjuvant ET (+/- CDK4/6 inhibitor) * Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1 * Adequate organ and marrow function Exclusion criteria: * Inoperable locally advanced or metastatic breast cancer * Pathological complete response following treatment with neoadjuvant therapy * History of any other cancer (except non-melanoma skin cancer or carcinoma in situ of the cervix or considered at very low risk of recurrence per investigator judgement) unless in complete remission with no therapy for a minimum of 5 years from the date of randomisation * Any evidence of severe or uncontrolled systemic diseases which, in the investigator's opinion precludes participation in the study or compliance * Known LVEF \<50% with heart failure NYHA Grade ≥2. * Mean resting QTcF interval \>480 ms at screening * Concurrent exogenous sex hormone therapy * Any concurrent anti-cancer treatment not specified in the protocol with the exception of bisphosphonates (e.g. zoledronic acid) or RANKL inhibitors (eg, denosumab) * Previous treatment with camizestrant, investigational SERDs/investigational ER targeting agents, or fulvestrant * Currently pregnant (confirmed with positive serum pregnancy test) or breastfeeding * Patients with known hypersensitivity to active or inactive excipients of camizestrant or drugs with a similar chemical structure or class to camizestrant. In pre-/peri-menopausal female and male patients, known hypersensitivity or intolerance to LHRH agonists, that would preclude the patient from receiving any LHRH agonist