Study on Genetically-Informed Therapy for ER+ Breast Cancer After CDK4/6 Inhibitor Treatment

Inclusion Criteria

• Women who are post-menopausal and 18 years or older with advanced ER+ breast cancer that has spread or returned and cannot be cured with surgery.
• Must have been treated with a CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) alone or with hormone therapy for advanced cancer.
  • Up to three additional treatments after CDK4/6 inhibitors are allowed.
  • Any number of previous hormone therapies is allowed.
  • Only one previous chemotherapy treatment is allowed.
• Must have a confirmed diagnosis of ER+ breast cancer through a biopsy or surgery.
  • Exceptions: Patients with mostly bone cancer or those who cannot safely have a biopsy but have a history of ER+ breast cancer are eligible without a new biopsy.
• Cancer must be HER2-negative based on specific lab tests.
• Genetic testing of the tumor or blood must have been done after the cancer progressed on CDK4/6 inhibitors, checking for specific genetic changes.
  • If not done, genetic testing will be performed as part of the study.
• Archived tumor tissue should be available for research if possible.
• Must have had recent imaging tests like PET/CT or bone scans as part of standard care.
• Must be willing and able to provide written consent to participate in the study.

Exclusion Criteria

• Currently being treated with abemaciclib.
• Cannot receive other cancer treatments during the study, except for bone-strengthening treatments like bisphosphonates or denosumab.
• Have received experimental cancer treatments in the last three weeks.
• Have untreated brain disease unless it has been stable for at least three months.