Is anti-hormone therapy with the already approved drug elacestrant helpful when the first signs of renewed disease activity (relapse) appear in the blood?

Breast cancer (mammary carcinoma) is a malignant disease of the mammary gland tissue characterized by the uncontrolled proliferation of mammary gland cells. Treatment of the disease depends on numerous factors, such as the patient’s overall health, 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). Patients with hormone receptor-positive breast cancer typically receive standard antihormonal therapy (including tamoxifen, letrozole, anastrozole, or exemestane). This treatment specifically targets the estrogen receptor. A new drug in the class of hormone receptor-targeted medications is elacestrant, a selective estrogen receptor degrader (SERD) that binds to the estrogen receptor and breaks it down. It has already been approved; however, its use is to be tested in a specific situation where there is no obvious evidence of renewed disease activity (recurrence), but where trace amounts of tumor cell components are detectable in the blood using new testing methods (liquid biopsy). This involves measuring circulating tumor DNA (ctDNA) in the blood.

The goal of this Phase 3 study is to investigate the efficacy and safety of treatment with elacestrant compared to standard anti-hormone therapy. A prerequisite for participation is the detection of ctDNA in the blood. This is assessed while patients are already receiving standard anti-hormone therapy.

Participants will be randomly assigned to 2 groups as part of the study. Group 1 (treatment arm) will receive the study drug elacestrant daily as a tablet. Group 2 (control arm) will continue to receive the standard anti-hormonal therapy that patients were already receiving at the time of tumor DNA measurement. The study is open-label, meaning that both the medical staff and the patients know which medications are being taken. The treatments and follow-up examinations as part of the study will continue for up to 5 years, during which the effectiveness of the therapy and the occurrence of side effects from the various medications will be evaluated. The primary objective is to determine whether treatment with elacestrant leads to better treatment outcomes (metastasis-free survival rate) compared to standard anti-hormone therapy.

Women and men aged 18 and older with hormone receptor-positive, HER2-negative breast cancer in stage 2B or 3 are eligible to participate in this study. Patients must also show a recurrence of tumor DNA while on anti-hormone therapy.