Breast Cancer Clinical Trials

• Female (regardless of menopausal status) or male ≥18 years of age;

• The patient has confirmed HR+, HER2-, early-stage resected invasive breast cancer candidate to adjuvant CDK4/6 inhibitors (abemaciclib or ribociclib);

• ER and PgR positivity is defined as evidence of immunohistochemical staining ≥ 1% according to ASCO/CAP recommendations; HER2 negativity is defined as expression of the membrane protein in immunohistochemistry 0 or 1+ or with a 2+ in situ hybridization (ISH) test negative as per ASCO/CAP recommendations;

• Patients who are initiating or have initiated adjuvant treatment with a CDK4/6 inhibitor (abemaciclib or ribociclib) in combination with endocrine therapy (ET). Treatment must have started on or after January 1, 2021.

• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2;

• Consent to data treatment according to the local regulation.