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 reproductive hormone therapy or non-topical hormonal therapy for
   non-cancer-related conditions

   - 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