What treatment outcomes does the newly approved combination therapy of ribociclib and standard antihormonal therapy deliver in everyday clinical practice?

Breast cancer (mammary carcinoma) is a malignant disease of the breast gland tissue in which cells multiply uncontrollably. Treatment depends on various factors, including the patient’s overall health, tumor stage, growth rate (e.g., Ki-67 index), hormone receptor status (estrogen/progesterone receptors), and HER2 status. As long as the cancer has not metastasized, the initial goal is to completely remove it through chemotherapy (usually neoadjuvant) followed by surgery. Depending on the risk, this is followed by further treatment (adjuvant), such as anti-hormone therapy. Before menopause, tamoxifen is usually used; after menopause, an aromatase inhibitor—either alone or in combination.

Ribociclib is a so-called CDK4/6 inhibitor that inhibits the growth of tumor cells by blocking the cell cycle and can thus enhance the effect of antihormonal therapy. The drug is now approved for the adjuvant treatment of HR-positive breast cancer in combination with anti-hormone therapy.

The goal of this Phase IIIb study is to further investigate this combination. All participants will receive ribociclib in combination with standard anti-hormonal therapy. The study is single-arm (no comparison arm) and open-label (not blinded). Ribociclib is taken once daily on days 1 through 21 of a 28-day treatment cycle. Up to 39 cycles are planned, followed by a follow-up visit 30 days after the end of therapy. In addition, follow-up examinations are scheduled for up to 48 months after the start of therapy for the last enrolled participant. The primary endpoint is the “invasive breast cancer-free survival” (iBCFS) rate at 3 years—that is, the proportion of patients who do not experience a recurrence.

Eligibility criteria include, among others: no metastases, no other ongoing or planned cancer treatments except anti-hormone therapy, and the disease must be at stage IIa, IIb, or III. Anti-hormone therapy that has already begun is permitted, provided it was initiated within the last 36 months and will continue for at least three more years.