This study aims to develop and prospectively validate a questionnaire to select patients with breast cancer who need to access to hospital for clinical visit during treatment with CDK4/6i, to improve patients' quality of life and reduce burden of hospital accesses.

Inclusion Criteria:

• Written informed consent.
• Age ≥18 years old
• Histologically or cytologically documented diagnosis of HR+, HER2-negative breast cancer based on local laboratory results and who are not amenable to resection or radiation therapy with curative intent. HR+ tumor is defined as ER and/or PgR expression in greater than 1% of tumor cells. HER2-negative breast cancer is defined as a negative in situ hybridization test or an immunohistochemistry (IHC) status of 0 or 1+. If IHC is 2+, a negative in situ hybridization (FISH, CISH, or SISH) test is required to confirm the HER2-negative status (based on the most recently analyzed tissue sample tested by a local laboratory).
• Currently on treatment and have received ≥ 2 months of CDK4/6i + hormone therapy as their initial endocrine based treatment for their metastatic disease in concordance with local CDK4/6i label or treatment guideline.
• No evidence of clinical or radiological disease progression per investigator assessment.
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤2.

Exclusion Criteria:

• History of significant neurological or psychiatric disorders that would prohibit the understanding and giving of informed consent.
• Patient has a concurrent invasive malignancy and /or is concurrently using other anti-neoplastic therapy.

Women with advanced HR-positive/Her2-negative Breast Cancer (BC) who have completed at least 2 cycles of a first-line therapy with CDK4/6i + hormone therapy and are currently on treatment.