Non-interventional Study to Assess the Effectiveness and Safety of Ribociclib in the Adjuvant Therapy of Hormone Receptor Positive (HR+) HER2-negative Stage II and III Breast Cancer in Real Clinical Practice in Russia

Inclusion Criteria: Patients from the prospective cohort of the study must meet all of the following criteria: 1. Signed and dated Informed Consent Form (ICF) not later than 28 days after the initiation of adjuvant therapy with ribociclib in combination with aromatase inhibitors (±GnRH agonists). 2. Age ≥18 years at the time of signing the ICF. 3. Histologically verified HR+ HER2-negative stage II-III breast cancer, for which radical treatment was carried out. 4. The adjuvant hormone therapy with aromatase inhibitors (±GnRH agonists) may be started not earlier than 12 months before initiation of therapy with ribociclib. 5. ECOG performance status 0-1 Patients from the retrospective cohort of the study must meet all of the following criteria: 1. Age ≥18 years at the initiation of hormone therapy. 2. Histologically verified HR+ HER2-negative stage II-III breast cancer, for which radical treatment was carried out. 3. Initiation of adjuvant hormone monotherapy with aromatase inhibitors (±GnRH agonists) in the index period from July 1, 2019 to July 1, 2020. 4. Presence of the necessary information in the source documentation. Exclusion Criteria: Patients enrolled in the study in prospective cohort should not meet any of the following criteria. 1. History of therapy with abemaciclib or palbociclib 2. Therapy with ribociclib in combination with AI for more than 28 days at the time of signing the Informed Consent Form 3. Active therapy for other malignant neoplasms 4. Participation in interventional clinical studies at the time of signing the Informed Consent Form Patients enrolled in the study in retrospective cohort should not meet any of the following criteria. 1. Neoadjuvant or adjuvant therapy with CDK4/6 inhibitors 2. A history of another concomitant malignant neoplasm requiring active therapy 3. Participation in interventional clinical studies at the time of treatment for breast cancer 4. Patients experiencing a recurrence during adjuvant hormone therapy can participate if they meet the other inclusion and exclusion criteria.