Evaluating the long-term effectiveness and safety of abemaciclib plus endocrine therapy for hormone receptor-positive, HER2-negative, node-positive, high-risk early breast cancer

The study evaluated the follow-up results of abemaciclib (Verzenio) plus endocrine (hormonal) therapy in patients with hormone receptor-positive (HR+), HER2-negative (HER2-), node-positive, and high-risk early breast cancer (BC). The data found that with a 4-year follow-up, adjuvant abemaciclib continued to show improvement in reducing the risk of recurrence in these patients.

BC is classified based on the presence or absence of receptors or proteins found on cancer cells. HR+ refers to positive female sex hormone receptors (such as estrogen and/or progesterone) and HER2- means BC cells do not have HER2 protein on the surface. HR+ and HER2- are found in about 70% of BCs.

Abemaciclib is a biological treatment that targets proteins and reduces the rate of cancer spreading. Past studies have led to the approval of the combination of abemaciclib and endocrine therapy in HR+, HER2- early BC. However, the previous follow-up was short. Longer-term studies are needed to further evaluate the effectiveness and safety of abemaciclib plus endocrine therapy in patients with HR+, HER2-, node-positive breast cancer. 

This study involved 5637 patients with HR+, HER2-, node-positive, high-risk early BC. Patients were randomly assigned into 2 groups. Group 1 included 2808 patients who received abemaciclib (150mg twice daily) and endocrine therapy. Group 2 included 2829 patients who received endocrine therapy alone. The endocrine therapies were either anti-estrogen agents such as tamoxifen (Nolvadex) or aromatase inhibitors. The average follow-up was 42 months.

After 4 years, 85.8% of patients in group 1 were alive without invasive disease compared to 79.4% in group 2. The difference in the average survival without invasive disease at 4 years was 6.4% compared to 2.8% at 2 years.

The most common side effects were neutropenia (white blood cell counts that fight off infections; 19.6% in group 1 compared to 0.9% in group 2), leucopenia (white blood cell counts; 11.4% in group 1 compared to 0.4% in group 2), and diarrhea (7.8% in group 1 compared to 0.2% in group 2). The most common severe side effects were infections (5.3% in group 1 compared to 2.9% in group 2) and digestive side effects (2.1% in group 1 compared to 0.6% in group 2).

The study concluded that abemaciclib and endocrine therapy continued to benefit patients with HR+, HER2-, node-positive, high-risk early BC in reducing the risk of invasive disease after 4 years.

The overall survival data was not established so more follow-up is needed. Patients knew which treatment were receiving. This might have influenced the results. This study was funded by Eli Lilly, the manufacturer of abemaciclib.