Prevalence, clinicopathologic features and long-term overall survival of early breast cancer patients eligible for adjuvant abemaciclib and/or ribociclib

Adjuvant CDK4/6 inhibitors (abemaciclib and ribociclib) associated with endocrine therapy reduced the risk of relapse for HR+/HER2- early breast cancer (eBC) patients in the monarchE and NATALEE trials. In this population-based study, we assess the real-life proportion, and long-term prognosis of patients treated for HR+/HER2- eBC between 2005 and 2015, and eligible for adjuvant CDK4/6 inhibitors according to these trial inclusion criteria. Among 3,103 patients, N = 440 (14.2%) would have been eligible for adjuvant abemaciclib, and N = 1068 (34.4%) for ribociclib. Node-negative patients who would have been eligible for adjuvant ribociclib represent 10.9% of the eligible population. 21.7% of patients now eligible for adjuvant abemaciclib, and 32.1% for ribociclib did not receive (neo)adjuvant chemotherapy. After a median follow-up of 144.7 months, 10-year overall survival confirms the prognostic relevance of the inclusion criteria used in pivotal trials. This study provides real-life insights into the prevalence, clinicopathological characteristics and long-term prognosis of HR+/HER2- eBC patients now eligible for adjuvant CDK4/6 inhibitors.