A trial to learn how camizestrant (AZD9833) works compared to fulvestrant and how safe it is in women with advanced breast cancer who have gone through menopause.

Prior treatment

• Intervention with any of the following: Any cytotoxic chemotherapy, investigational agents or other anti-cancer drugs for the treatment of breast cancer from a previous treatment regimen or clinical study within 14 days of the first dose of study treatment.
• Refractory nausea and vomiting, uncontrolled chronic gastrointestinal diseases, inability to swallow the formulated product, or previous significant bowel resection that would preclude adequate absorption of AZD9833.
• Previous randomisation in the present study.
• Use of systemic oestrogen-containing hormone replacement therapy within 6 months prior to the first dose of study treatment.
• Medications or herbal supplements known to be strong inhibitors/inducers of cytochrome P450 and as specified in Appendix B of the protocol, prior to receiving the first dose of study treatment.
• Drugs as indicated in Appendix B1 of the protocol.
• Radiotherapy with a limited field of radiation for palliation.
• Major surgical procedure or significant traumatic injury.

Other illness

• History of hypersensitivity to active or inactive excipients of AZD9833 or fulvestrant.
• Immunocompromised patients, eg, patients who are known to be serologically positive for human immunodeficiency virus (HIV).
• Patients with known active hepatitis (i.e. hepatitis B or C).
• Presence of life-threatening metastatic visceral disease or uncontrolled central nervous system (CNS) metastatic disease.

Other

• Women of childbearing potential.
• Any cardiovascular criteria described in the protocol.
• Inadequate bone marrow reserve or organ function.

• Provision of signed and dated, written informed consent prior to any mandatory study specific procedures, sampling, and analyses. Patients are also required to consent to the provision of archival tumour biopsies.
• Patients must have at least 1 lesion, not previously irradiated, that can be measured accurately at baseline as ≥10 mm in the longest diameter or in absence of measurable disease as defined above, at least 1 lytic or mixed (lytic+sclerotic) bone lesion.
• Eastern Cooperative Oncology Group (ECOG)/World Health Organisation (WHO) performance status 0 to 1.Inclusion criterion for the paired tumour biopsy research subgroup.
• Washout from prior tamoxifen: 4 months to elapse from last tamoxifen dose to pre-dose on-study biopsy.
• For patients who consent, provision of signed and dated written informed consent prior to collection of sample for analysis.
• Female patients aged at least 18 years.
• Post-menopausal as per the defined criteria.
• Histologically or cytological confirmation of adenocarcinoma of the breast.
• ER-positive status of primary or metastatic tumour tissue.
• HER2-negative
• Metastatic disease or loco-regionally recurrent disease suitable for treatment with fulvestrant.
• Radiological or other objective evidence of progression on or after the last systemic therapy prior to starting study treatment.