Study of a Novel Antihormonal Drug in the Adjuvant Setting for Patients at 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), 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.

Treatment is typically divided into two phases (neoadjuvant and adjuvant), unless metastases are already present. Neoadjuvant therapy constitutes the first phase. This is followed by breast surgery. Depending on the disease’s risk profile, adjuvant therapy usually follows, which involves antihormonal therapy for hormone receptor-positive breast cancer. One group of medications used in standard anti-hormone therapy includes aromatase inhibitors such as anastrozole, letrozole, and exemestane; another group consists of “selective estrogen receptor modulators” (SERMs), which include tamoxifen.

The goal of the CAMBRIA-1 study is to evaluate the efficacy and safety of camizestrant, a new drug in the SERM class, compared to standard therapy. Patients must have been receiving adjuvant anti-hormone therapy for at least 2 and no more than 5 years. If they are currently receiving a CDK4/6 inhibitor such as abemaciclib as part of this treatment, this therapy must first be discontinued. The patients will then be randomly assigned to two groups. One group (control arm) will receive standard antihormonal therapy, with the specific drug selected by the treating physician; the other group (study arm) will receive the new drug camizestrant.

The duration of treatment depends on when—or if—the breast cancer returns (recurrence). Follow-up will continue for up to 10 years. The drug has already been studied in smaller Phase II trials, where it demonstrated benefits over standard therapy. Patients know which study arm they are in.

Women and men aged 18 and older with hormone receptor-positive, HER2-negative early-stage breast cancer (stages 0–2) are eligible to participate in the study. The breast cancer must have already been treated surgically. Patients must have a moderate or high risk of recurrence. Patients must have received anti-hormone therapy with an established standard medication for at least 2 years, but for no more than 5 years.