This phase II trial studies how well imlunestrant and abemaciclib work in treating patients with estrogen receptor positive (ER+) breast cancer who have tumor remaining in the blood following treatment (minimal residual disease). Estrogen can cause the growth of breast cancer cells. Imlunestrant lowers the amount of estrogen made by the body. This may help stop the growth of tumor cells that need estrogen to grow. Abemaciclib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Imlunestrant and abemaciclib may be effective in treating patients with ER+ breast cancer who have minimal residual disease.
Eligibility criteria
Qualifiers
Participants must have localized ER+ (≥ 10% on surgical pathology), HER2 negative, any grade, invasive breast cancer. Pathological stage (from time of surgery, including patients who received neoadjuvant therapy) I - III by American Joint Committee on Cancer (AJCC) 8th edition staging
Note: Invasive breast cancer must be ER+ in ≥ 10% of the cells and HER2 negative (immunohistochemistry [IHC] 0 or 1+ and/or fluorescence in situ hybridization [FISH] negative with a ratio < 2) by American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines. For Immunohistochemistry (IHC) 2+, the tumor must be FISH negative with a ratio < 2. ER, progesterone receptor (PR) and HER2 measurements should be performed according to institutional (local) guidelines, in a Clinical Laboratory Improvement Act (CLIA)-approved setting
Detectable ctDNA in a CLIA-certified lab (separate pre-screening consent available) within the past six months. Participants must have no clinical or radiographic evidence of recurrence as determined by the treating investigator
Confirmation of adequate archival tissue (either initial biopsy or surgical specimen) (15-20 unstained slides cut at 5 µm or 1 block) required before study entry. If adequate surgical tissue is available, this is preferred. Otherwise tissue from diagnostic biopsy is acceptable. If adequate tissue not available, principal investigator (PI) approval is required prior to study entry
Disqualifiers
Participants with metastatic disease (including contralateral axillary lymph nodes) or inflammatory breast cancer. Of note, if a patient had locally advanced breast cancer leading to inflammation, this would not exclude the patient on the grounds of inflammatory carcinoma
Participants who have had CDK 4/6 inhibitor therapy within the past 6 months. Use of prior CDK 4/6 inhibitor with last dose more than 6 months ago is permitted
Participants who are receiving any other anti-cancer investigational agents. Participation in other observational studies is permitted
History of other malignancies within past 5 years, except ductal carcinoma in situ of the breast, cervical cancer in situ, melanoma in situ, and basal cell or squamous cell carcinoma of the skin. No concurrent malignancy or other serious medical condition as deemed by the investigator