Real-world data on patients with early breast cancer who were prescribed abemaciclib adjuvant therapy in Japan.

To understand the real-world use of abemaciclib in Japanese patients with early breast cancer (EBC). This retrospective observational study was conducted using a Japanese administrative claims database in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative EBC who received abemaciclib adjuvant therapy from December 2021-March 2023. Patient characteristics and treatment patterns were summarized. Among 374 patients, 38.2, 51.6 and 63.4% patients received neoadjuvant chemotherapy, adjuvant chemotherapy and radiotherapy, respectively; 13.1% were chemotherapy naive. Tamoxifen (37.7%), letrozole (35.6%), anastrozole (24.3%) were the commonly prescribed concomitant adjuvant endocrine therapies. Abemaciclib dose reductions were observed in 42.0% patients. Use of abemaciclib for treatment of high-risk EBC was described, which could help inform patient selection and treatment patterns.