New drug (Imlunestrant) for the treatment of early-stage hormone receptor-positive breast cancer with a high 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 tumor’s growth rate (Ki-67 index), detectable hormone receptors (HR) 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.

Treatment for early-stage breast cancer (stages 1–2) typically involves breast-conserving surgery with the goal of complete recovery. To reduce the risk of recurrence, chemotherapy is administered before surgery in certain cases (neoadjuvant). To minimize the risk of residual disease even after surgery, further therapy (adjuvant) is administered after surgery in many cases, depending on certain risk factors. In addition to radiation therapy or chemotherapy, hormone receptor-positive breast cancer is routinely treated with a specific anti-hormone therapy, which involves the use of, for example, tamoxifen or the aromatase inhibitors anastrozole, letrozole, and exemestane. The new drug imlunestrant, an estrogen receptor blocker, has already been investigated in initial studies and could represent a new treatment option. The drug has not yet been approved for the treatment of breast cancer.

The goal of this Phase 3 study is to investigate the efficacy and safety of Imlunestrant compared to standard anti-hormone therapies. As part of the study, patients will be randomly assigned to one of two groups. Group 1 (study arm) will receive the study drug imlunestrant in tablet form as therapy following surgery. Group 2 (control arm) receives standard anti-hormone therapy with tamoxifen, anastrozole, letrozole, or exemestane (the exact regimen is selected by the treating physicians).

The study is open-label, meaning that both the medical staff and the patient know which medications are being taken. The treatments and follow-up examinations as part of the study will continue for up to 10 years, during which the effectiveness 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 treatment.

Women and men aged 18 and older with hormone receptor-positive, HER2-negative early-stage breast cancer (stages 1–2) are eligible to participate in this study. The breast cancer must have already been surgically removed, and there must be an increased risk of the disease returning (recurrence). Standard anti-hormone therapy must have been administered for at least 2 years and no more than 5 years at the time the study begins.