A prospective cohort study of abemaciclib-induced interstitial lung disease in metastatic breast cancer after chemotherapy

The safety of combination therapy with abemaciclib and hormone therapy in patients with hormone receptor-positive (HR +), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) who were previously treated with chemotherapy for MBC remains unclear. Caution is required as the Pharmaceuticals and Medical Devices Agency (PMDA) and the U.S. Food and Drug Administration (FDA) have issued warnings about abemaciclib-induced interstitial lung disease (ILD).

This study was a secondary analysis of a prospective observational study involving patients who had previously undergone chemotherapy for HR + MBC. A certificated respiratory specialist reviewed the clinical information of patients who were suspected of having ILD to adjudicate abemaciclib-induced ILD and definitively diagnosed abemaciclib-induced ILD. In this study, the incidence, risk factors, and clinical course of interstitial lung disease (ILD) are reported.

All cases of patients who received abemaciclib had no radiological evidence of ILD prior to abemaciclib treatment. The incidence of abemaciclib-induced ILD was 7.4% (n = 9/122). CTCAE grade 1/2 occurred in 77.8% (n = 7), with no grade 4/5 cases. The timing of ILD onset varied and our study did not identify any significant risk factors for abemaciclib-induced ILD. All cases of ILD ultimately were confirmed to be in remission or cured.

In this multicenter prospective cohort study with a follow-up period of 3.3 years and a definition of ILD by a certified pulmonologist, we accurately evaluated abemaciclib-associated ILD after chemotherapy. The favorable clinical course of ILD indicate that abemaciclib treatment is an acceptable option for these MBC patients. However, because abemaciclib-induced ILD is difficult to predict, careful monitoring is required during abemaciclib treatment.