New Combination Therapy for Early-stage Breast Cancers
Some patients with stage 2 or 3 breast cancer may now receive ribociclib with an aromatase inhibitor after surgery.
The U.S. Food and Drug Administration (FDA) has approved ribociclib (Kisqali) in combination with an aromatase inhibitor as adjuvant therapy for patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative stage 2 or 3 breast cancer that has a high risk of recurring.
The FDA also approved a co-pack of ribociclib and the aromatase inhibitor letrozole (Kisqali Femara Co-pack) for this same patient population.
Ribociclib is a targeted therapy that inhibits the proteins CDK4 and CDK6. These proteins promote cell division, so blocking their activity helps slow down the growth and spread of cancer. Aromatase inhibitors, including letrozole, block the production of estrogen, a hormone that drives the growth of HR-positive breast cancers.
Ribociclib, combined with either an aromatase inhibitor or another type of therapy targeting estrogen’s effects, was previously approved to treat certain patients with advanced HR-positive, HER2-negative breast cancer. The latest approval makes ribociclib with aromatase inhibition available to some patients with early-stage disease as well.
The approval was based on results from the randomized, open-label, multicenter, phase III NATALEE clinical trial, which enrolled 5,101 patients with stage 2 or 3 HR-positive, HER2-negative breast cancer with high-risk features. Patients were randomly assigned (1:1) to receive either ribociclib plus an aromatase inhibitor or an aromatase inhibitor alone.
Compared to patients in the aromatase inhibitor-only arm, those assigned to the ribociclib arm were 25% less likely to experience disease recurrence, death from any cause, invasive breast cancer in the other breast, or another cancer outside the breast within 36 months of assignment to a treatment arm. After 36 months, 90.7% of patients assigned to the ribociclib arm were alive and disease-free, as compared with 87.6% of patients assigned to aromatase inhibition alone. These results were presented at the 2023 San Antonio Breast Cancer Symposium, co-organized by the American Association for Cancer Research.
The recommended dose of adjuvant ribociclib is 400 mg daily in 28-day cycles (drug taken for 21 consecutive days, followed by seven days without the drug). The recommended dose for the aromatase inhibitor varies based on the aromatase inhibitor used.
Breast cancer is the most common nonskin cancer diagnosed in women and the second-leading cause of cancer-related death in women. Breast cancers are classified into subtypes based on whether they express certain cell surface markers, including HR and HER2. Seventy percent of breast cancers are HR-positive and HER2-negative. According to federal statistics, it was estimated that 310,720 individuals would be diagnosed with breast cancer and 42,250 patients would die of the disease in the United States in 2024.
The FDA rendered its decision on September 17, 2024.
