The purpose of this study is to evaluate the efficacy and safety of ctDNA-guided initiation of CDK4/6 inhibitor therapy using the Signatera™ Designed on Genome test (referred to as "Signatera Genome") in participants with intermediate-risk HR+/HER2- early-stage breast cancer. Based on ctDNA test results, participants will either start CDK4/6 inhibitor therapy in addition to hormone therapy or continue hormone therapy with ongoing ctDNA surveillance. This study will compare outcomes to historical controls from the NataLEE trial to determine whether ctDNA-guided timing maintains efficacy while reducing unnecessary treatment. Participants will be followed for up to 9 years with regular blood draws, hormone therapy, imaging as needed, and quality-of-life assessments.
Signed and dated Informed Consent Form (ICF) obtained prior to any trial-specific screening procedure.
Patient is ≥ 18 years-old at the time of ICF signature.
Patient is female with known menopausal status at the time of initiation of adjuvant endocrine therapy (ET), or male.
Patient with histologically confirmed unilateral and unifocal primary invasive adenocarcinoma of the breast prior to initiating adjuvant chemotherapy, if indicated, or within 6 months of initiating adjuvant endocrine therapy if chemotherapy is not indicated. Patients who receive neoadjuvant endocrine therapy or chemotherapy are allowed to enroll.
Patient has had prior exposure to a CDK4/6 inhibitor.
Patient is concurrently using hormone replacement therapy.
Patient with a known contraindication or hypersensitivity to ribociclib or abemaciclib as per the FDA indication label.
Patients with a multicentric and/or multifocal and synchronous contralateral breast cancer are ineligible.