This clinical trial is focused on studying treatments for Advanced Breast Cancer, specifically in patients with certain genetic mutations known as BRCA1, BRCA2, or PALB2. The trial will explore the effectiveness and safety of a combination of two medications: Saruparib (also known by its code name AZD5305) and Camizestrant. These medications will be compared to the current standard treatment options, which include a type of medication called CDK4/6 inhibitors combined with Endocrine Therapy or Camizestrant alone. The study aims to determine if the new combination of Saruparib and Camizestrant is more effective in delaying the progression of the disease.

Participants in the study will receive either the new combination treatment or one of the standard treatments, which will be chosen by their doctor. The study will monitor how long the cancer remains stable without getting worse, as well as the overall survival of the participants. The trial will also assess the time it takes for participants to start chemotherapy after the study treatment, the response of the cancer to the treatment, and the duration of any positive response. Additionally, the study will gather information on the side effects experienced by participants, focusing on symptoms like diarrhea and abdominal pain, and how these affect their quality of life.

The trial will also measure the levels of Saruparib and Camizestrant in the blood to better understand how these drugs work in the body. The study is expected to start recruiting participants in late 2024 and will continue until 2030. This research is important for developing new treatment options for people with Advanced Breast Cancer who have specific genetic mutations, and it aims to improve the outcomes and quality of life for these patients.