monarchE: This phase III trial is evaluating the addition of an oral drug (Abemaciclib) to standard adjuvant endocrine therapy in patients with high risk, early stage, hormone receptor and node positive, HER 2- breast cancerA Randomized, Open-Label, Phase 3 Study of Abemaciclib Combined With Standard Adjuvant Endocrine Therapy Versus Standard Adjuvant Endocrine Therapy Alone in Patients With High Risk, Node Positive, Early Stage, Hormone Receptor Positive, Human Epidermal Receptor 2 Negative, Breast Cancer

Exclusion

• Metastatic disease (including contralateral axillary lymph nodes) or node-negative disease.
• Participants with inflammatory breast cancer.
• Participants with a history of previous breast cancer, with the exception of ipsilateral ductal carcinoma in situ (DCIS) treated by locoregional therapy alone ≥5 years ago. Participants with a history of contralateral DCIS treated by local regional therapy at any time may be eligible. Participants with a history of any other cancer (except non-melanoma skin cancer or carcinoma in situ of the cervix), unless in complete remission with no therapy for a minimum of 5 years from the date of randomization are excluded.
• Females who are pregnant or lactating.
• The participant has previously received treatment with any CDK4 and CDK6 inhibitor.
• The participant is receiving concurrent exogenous reproductive hormone therapy (for example, birth control pills, hormone replacement therapy, or megestrol acetate).
• The participant has previously received endocrine therapy for breast cancer prevention (tamoxifen or aromatase inhibitors) or raloxifene.
• The participant has serious preexisting medical condition(s) that, in the judgment of the investigator, would preclude participation in this study.
• The participant has a personal history of any of the following conditions: syncope of cardiovascular etiology, ventricular arrhythmia of pathological origin or sudden cardiac arrest. Any participant with a history of venous thromboembolism (VTE).
• The participant has active systemic infections or viral load.
• The participant has received an experimental treatment in a clinical trial within the last 30 days or 5 half-lives, whichever is longer.