Observational Study of the Combination Therapy of Ribocliclib and an Aromatase Inhibitor in Early-Stage Hormone-Receptor-Positive/HER2-Negative Breast Cancer

Breast cancer (mammary carcinoma) is a malignant disease of the breast gland in which cells in the breast gland multiply uncontrollably. In the early stages, the cancer is confined to the breast and has not yet spread to other organs. Treatment depends on various factors, including whether hormone receptors (e.g., for estrogen or progesterone) or the HER2 receptor are present on the tumor’s surface. Hormone therapy can specifically inhibit the growth of such tumors. Aromatase inhibitors (NSAIs, e.g., letrozole) are typically used for this purpose. In premenopausal patients, a GnRH analog (LHRH, e.g., goserelin) may also be necessary to suppress the body’s own hormone production. To further reduce the risk of recurrence, high-risk patients may also be treated with a so-called CDK4/6 inhibitor such as ribociclib or abemaciclib. This class of drugs specifically interferes with the cell cycle and further slows tumor growth. Ribociclib is already approved as a standard treatment for advanced breast cancer and is increasingly being used in early stages as well. The HER2 receptor is also frequently found on breast cancer cells. An increased presence of this receptor on cancer cells also promotes cell growth. However, study participants should not exhibit this characteristic (HER2-negative).

The CAROLEEN study is investigating how this combination therapy performs in everyday clinical practice. It aims to gather information on side effects, quality of life, and adherence to treatment in everyday life and will monitor the patients for 36 months for this purpose. This is a non-interventional observational study, which means no additional medication is administered. Treatment proceeds as usual according to the physician’s decision, and the study simply supports patients by documenting their experiences.

The goal of the study is to investigate the efficacy, safety, and tolerability of treatment with ribociclib and aromatase inhibitors in patients with early-stage hormone receptor-positive/HER2-negative breast cancer. The study is open-label and unblinded, meaning that patients and physicians are aware of the treatment arm. Three approved treatment strategies are being compared: ribociclib + aromatase inhibitor ± GnRH analog, abemaciclib + anti-hormonal therapy ± GnRH analog, and anti-hormonal therapy alone ± GnRH analog.

Women and men aged 18 and older with early-stage hormone receptor-positive/HER2-negative breast cancer are eligible to participate if they have received treatment with ribociclib + aromatase inhibitor (NSAI) ± GnRH analog (LHRH), with abemaciclib + anti-hormonal therapy (ET) ± LHRH, or with anti-hormonal therapy alone ± LHRH within the last 14 days. The cancer must be associated with a high risk of recurrence. Patients who are simultaneously participating in other studies with ribociclib or who have already received anti-hormonal therapy for an extended period are excluded.