Study on Nonsteroidal Aromatase Inhibitors and Abemaciclib for Postmenopausal Women with Breast Cancer

Inclusion Criteria

• Have hormone receptor-positive (HR+) and HER2-negative breast cancer.
• Have cancer that has come back in the same area and cannot be removed or treated with radiation to cure it, or have cancer that has spread to other parts of the body.
• Be postmenopausal.
• Have either measurable cancer or cancer that is only in the bones and cannot be measured.
• Be in good overall health with a performance status of 0 or 1 on the ECOG scale, meaning fully active or restricted in physically strenuous activity but ambulatory.
• Have good organ function based on medical tests.
• Have stopped any previous localized radiation therapy for pain relief or bone lesions at risk of fracture and have recovered from its immediate effects.
• Be able to swallow capsules.

Exclusion Criteria

• Have severe symptoms from cancer affecting organs, widespread cancer in the lungs, or cancer in the brain or spinal cord.
• Have inflammatory breast cancer.
• Have cancer that has spread to the brain or spinal cord, or a history of such spread.
• Are currently receiving or have previously received hormone therapy for cancer that has come back or spread.
• Have had hormone therapy after surgery with cancer returning within 12 months of finishing treatment.
• Are currently receiving or have previously received chemotherapy for cancer that has come back or spread.
• Have been treated with the drug everolimus before.
• Have been treated with any CDK 4/6 inhibitor before or participated in a trial for such drugs where the treatment is still unknown.
• Have started bone-strengthening treatments less than 7 days before joining the study.
• Are currently taking an experimental drug in another clinical trial or participating in other medical research that conflicts with this study.
• Have taken a drug not approved for any use within 14 or 21 days before joining the study, depending on the type of drug.
• Have had major surgery within 14 days before joining the study.