Comparison of Elacestrant with Standard Anti-Hormonal Therapy in Early-Stage, Hormone-Receptor-Positive, and HER2-Negative Breast Cancer with an Increased Risk of Recurrence

Breast cancer (mammary carcinoma) is a malignant disease of the breast gland tissue characterized by the uncontrolled proliferation of breast gland cells. Treatment of the disease depends on numerous factors, such as the patient’s overall health, the stage of the disease, the presence of detectable hormone receptors on the surface of the cancer cells (estrogen receptor- or progesterone receptor-positive) and the increased presence of the HER2 receptor on the cells (HER2-positive). Early-stage hormone receptor-positive and HER2-negative breast cancer is usually treated with anti-hormone therapy for several years following surgery. This therapy is intended to block the effect of estrogen on the cancer cells or reduce the amount of estrogen in the body, thereby lowering the risk of recurrence. The study drug, elacestrant, belongs to the class of selective estrogen receptor downregulators (SERDs) and is taken as a tablet. The study drug binds to the estrogen receptor alpha (ERα) in the cancer cells, inhibits it, and simultaneously promotes its breakdown, thereby interrupting the growth signal mediated by this receptor. Elacestrant is already approved for the treatment of hormone receptor-positive, HER2-negative, locally advanced or metastatic breast cancer in a specific treatment setting. However, the drug is not yet approved for the treatment of early-stage hormone receptor-positive and HER2-negative breast cancer. The treatment can be supplemented with a CDK4/6 inhibitor (ribociclib), which is intended to slow the proliferation of tumor cells by blocking the proteins CDK4 and CDK6.

The goal of this Phase 3 study is to investigate the efficacy and safety of treatment with elacestrant compared to standard anti-hormone therapy. As part of the study, patients will be randomly assigned to two groups. In the study arm, patients will receive elacestrant for five years, and in the control arm, patients will receive standard anti-hormonal therapy for five to ten years. If treatment with a CDK4/6 inhibitor is also indicated, ribociclib may be added concurrently for three years in the treatment arm, while the control arm will receive the corresponding standard treatment. The study is open-label, which means that both the study physicians and the patients know which treatment is being administered.

Patients aged 18 and older with newly diagnosed hormone receptor-positive and HER2-negative breast cancer are eligible to participate in this study. They must have an increased risk of recurrence, and no distant metastases may have developed.