Opciones de tratamiento para el cáncer de mama avanzado HR+/HER2- con mutación en ESR1

This is a prospective, non-interventional real-world study to observe the efficacy and safety of different treatment regimens in patients with ESR1-mutated HR+/HER2-advanced breast cancer after failure of endocrine therapy. Epidemiological data, efficacy and safety measures will be collected for each subject. Data on efficacy and safety assessment indicators will be collected every 2-3 months until disease progression, receipt of a new anti-tumour treatment modality, death, loss to follow-up, and arrival at the data collection cut-off date. The cut-off date for data collection is defined as 8 weeks after completion of 6 visits for each subject, or 4 weeks after treatment discontinuation and subject discontinuation/withdrawal. Subjects receiving a different treatment regimen remained subject to assessment of safety indicators 4 weeks after discontinuation of the original treatment regimen.