A Real-World Study in Patients With HR+/HER2- Advanced Breast Cancer

Safety and Effectiveness in Patients With HR+/HER2- Advanced Breast Cancer: a Prospective, Noninterventional Real-world Study

The goal of this observational study is to learn about the safety and effectiveness of people with advanced breast cancer that is hormone receptor-positive (HR+), HER2-negative (HER2-).

Participants will:

Allow researchers to collect medical data during routine care

Be followed for signs of treatment effectiveness and any medical problems that happen while taking the drug

Inclusion Criteria:

• 1. must have a histologically or cytologically confirmed diagnosis of breast cancer and evidence of locally advanced or metastatic disease that is not amenable to surgical resection.

  2. Women or men ≥ 18 years of age. 3. must be confirmed as HR+ and HER2- by local laboratory tests. Confirmation of this status can be done by a first visit tissue sample or a post-treatment sample (recent biopsy sample preferred if available).

  4. Testing to confirm ESR1 mutation positivity should be performed on tumor DNA taken from tissue samples or circulating tumor DNA (ctDNA) obtained from plasma samples using a well-validated assay. Accept the results of the central laboratory or local laboratory tests, and in the event of inconsistency between the two test results, the investigator determines whether enrollment is possible.

  5. previous treatment with at least one endocrine therapy, either as monotherapy or in combination with another drug, at an advanced stage.

  6. have a life expectancy greater than 3 months and normal organ function (as assessed by the investigator).

Exclusion Criteria:

- 1. Pregnant or lactating females. 2. Known difficulty tolerating oral medications, or the presence of conditions that would interfere with the absorption of oral medications or allergies to medications and their excipients.

3. Other conditions that the investigator considers inappropriate for enrollment.