Characteristics of real-world NATALEE- and monarchE-eligible populations with HR+/HER2- early breast cancer: A United States electronic health records database analysis

Despite standard-of-care adjuvant endocrine therapy (ET) and chemotherapy, the risk of recurrence remains in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2−) early breast cancer (EBC). In phase III trials with different eligibility criteria, adjuvant ribociclib (NATALEE) and abemaciclib (monarchE) demonstrated significant invasive disease survival benefit when added to ET. We present a real-world analysis of patients with HR+/HER2− EBC that are potentially eligible for NATALEE and monarchE.

Data from the ConcertAI Patient360 database (January 2015-January 2023) were analyzed. The key inclusion criteria were patients ≥18 years of age with stage I-III HR+/HER2− EBC at diagnosis who had surgery and initiated adjuvant ET. NATALEE and monarchE eligibility criteria were defined per their respective trial protocols.

Overall, 7060 patients met the inclusion criteria, of whom 30.6% were eligible for NATALEE and 14.5% for monarchE. All patients with N2 or N3 disease were eligible for both trials. Among 1388 (19.7%) patients with N1 disease, 91.8% and 45.9% were eligible for NATALEE and monarchE, respectively. Patients with N0 disease were 74.9% of the population, of whom 9.5% were eligible for NATALEE and none for monarchE. Among the NATALEE-eligible patients with high-risk N0 disease, most were postmenopausal (72.6%) with a grade 3 tumor (61.6%); 48.9% had received prior chemotherapy.

The results from this large real-world database study indicate that 30.6% of patients with HR+/HER2− EBC met the eligibility criteria for NATALEE versus 14.5% for monarchE, presenting the opportunity to improve outcomes in nearly one-third of patients with HR+/HER2– EBC at high risk of recurrence.