Development of a New Remote Monitoring Model for Patients With HR+HER2- Breast Cancer in Treatment With CDK4/6 Inhibitors and Hormone Therapy

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.