Extended antihormonal therapy with the addition of abemaciclib (a drug that inhibits cell growth) compared with antihormonal therapy alone in patients at high risk of recurrence

Breast cancer (mammary carcinoma) is a malignant disease of the mammary gland tissue characterized by the uncontrolled proliferation of mammary gland cells. In its early stages, the disease is confined to the breast. As the disease progresses, it often spreads to the lymph nodes and forms metastases throughout the body (bones/organs). This is referred to as metastatic disease, which corresponds to stage 4.

Treatment of the disease depends on numerous factors, such as the patient’s overall health, the stage of the disease, the tumor’s growth rate (Ki-67 index), the presence of detectable hormone receptors on the surface of the cancer cells (estrogen receptor-positive, progesterone receptor-positive), and the increased presence of HER2 receptors on the cells (HER2-positive). Cancer cells often have hormone receptors, making anti-hormone therapy a core element of treatment. Since the effectiveness of anti-hormone therapy can diminish over the course of the disease due to changes in the tumor cells (development of resistance), anti-hormone therapy is now frequently combined directly with a CDK4/6 inhibitor. This is a relatively new class of drugs that can further slow the growth of malignant cells. Abemaciclib has already been approved for this purpose and has proven to be very effective in studies. What has not yet been investigated is whether, in patients who have previously received only anti-hormonal therapy, the additional administration of abemaciclib is still effective even if the combination therapy is not administered right from the start but is initiated later in the course of treatment, or even when the standard anti-hormonal therapy is scheduled to be discontinued.

The goal of the ADAPTlate study is to investigate the efficacy and safety of extended (adjuvant) therapy with abemaciclib in combination with anti-hormone therapy compared to standard anti-hormone therapy alone. Participants will be randomly assigned to 2 groups as part of the study. Group 1 (study arm) will receive endocrine therapy (selected by the treating physician) following initial treatment, plus 150 mg of abemaciclib twice daily in tablet form for 24 months. Group 2 (control arm) will receive standard anti-hormonal therapy in accordance with current guidelines following initial treatment. The study is open-label, meaning that both the medical staff and the patient know which medications are being taken. Treatments and follow-up examinations as part of the study will continue for up to 6 years, during which the efficacy of the therapy and the occurrence of side effects from the various medications will be evaluated. The key factor is whether or when the disease recurs during therapy.

Female patients aged 18 and older, whether premenopausal or postmenopausal, with hormone receptor-positive, HER2-negative breast cancer at a locally confined stage are eligible to participate in this study. The disease must be classified as high-risk, and the patient must have already undergone surgery, radiation therapy, or chemotherapy. There must be no metastases. Recurrence of the disease is not a criterion for exclusion from the study; however, the recurrence must be in the breast itself and not elsewhere.