A Multicenter, Observational Study on the Real-World Effectiveness and Safety of inavolisib Combined with Endocrine Therapy With or Without a CDK4/6 Inhibitor in Patients with HR-Positive/HER2-Negative, PIK3CA-Mutated Advanced Breast Cancer.

Inclusion Criteria:

• Histologically or cytologically confirmed HR+/HER2- recurrent or metastatic breast cancer.
• Presence of a pathogenic PIK3CA mutation confirmed by tissue or plasma-based NGS/PCR testing.
• Availability of traceable electronic medical records, imaging, laboratory, and follow-up data at baseline.
• Initiated treatment with "Inavolisib + Endocrine Therapy" with or without a CDK4/6 inhibitor in real-world clinical practice, with complete and traceable regimen information.
• Provision of informed consent for this non-interventional study (if required by the center's ethics committee).

Exclusion Criteria:

• Concurrent participation in any interventional clinical trial at enrollment.
• Presence of another active malignancy requiring concurrent systemic therapy, or missing core data preventing outcome assessment.
• Any condition (psychiatric, social, geographical) that would preclude adequate follow-up, as judged by the investigator.

HR-Positive/HER2-Negative, PIK3CA-Mutated Advanced Breast Cancer