Monitoring Treatment Adherence with Abemaciclib in the Treatment of Early-Stage Breast Cancer with a High Risk of Recurrence

Breast cancer (mammary carcinoma) is a malignant disease of the breast glandular tissue and can be classified and treated accordingly based on the surface profile of the tumor cells (receptor profile). Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer is a form of breast cancer in which the tumor cells possess binding sites (receptors) for the hormones estrogen or progesterone but do not exhibit elevated levels of the HER2 receptor. The hormones estrogen and progesterone can bind to the cancer cells and stimulate them to grow and divide. At the same time, the presence of hormone receptors also provides targets for targeted therapies such as anti-hormone therapies. In hormone receptor-positive breast cancer, CDK4/6 inhibitors can be used in addition to anti-hormone therapy. CDK4/6 inhibitors specifically block enzymes that drive the cell cycle of cancer cells and are thus intended to slow down uncontrolled cell division. The study drug, which contains the active ingredient abemaciclib, belongs to the class of CDK4/6 inhibitors and is taken as a tablet.

The goal of this observational study is to retrospectively (retrospectively) to investigate how many patients are still continuing therapy with abemaciclib six months after starting treatment and to draw conclusions regarding treatment adherence or persistence. The study will not interfere with the treatment. At the time of the study, the patients were already receiving abemaciclib as part of their regular, medically prescribed treatment (abemaciclib treatment period: January 2023 through June 2025). A total of up to 200 patients are to be enrolled in the study. Patients will be selected from up to 30 study centers (certified breast cancer centers) throughout Germany.

Women aged 18 and older who have been diagnosed with early-stage HR-positive, HER2-negative breast cancer without distant metastases and who have been prescribed abemaciclib in accordance with the prescribing information are eligible to participate in the study. Treatment with abemaciclib must have taken place between January 2023 and June 2025. Patients with locally advanced or metastatic breast cancer are not eligible to participate.