49 Clinical Characteristics and Treatment Persistence in US Patients With HR+/HER2–, Node-Positive Early Breast Cancer Treated With Abemaciclib: Real-World Study From First Year After Approval

49 Clinical Characteristics and Treatment Persistence in US Patients With HR+/HER2–, Node-Positive Early Breast Cancer Treated With Abemaciclib: Real-World Study From First Year After Approval

Background

Abemaciclib in combination with endocrine therapy (ET) is approved for adjuvant treatment of adult patients with hormone receptor–positive/HER2-negative (HR+/HER2–), node-positive, early breast cancer at high risk of recurrence. This retrospective study describes clinical characteristics and treatment persistence in patients with HR+/HER2–, node positive early breast cancer initiating abemaciclib.

Materials and Methods

Data were accessed from the Flatiron Health electronic database. Adult patients with node-positive, stage I to III early breast cancer-initiating abemaciclib from October 2021 (FDA approval) to November 2022 at 150 mg twice daily (BID) were analyzed. The persistence rate was defined as the percentage of patients remaining on abemaciclib at 3 months, allowing for a 60-day or less medication gap.

Results

A cohort of 354 patients with a median follow-up time from abemaciclib initiation of 8.8 months were selected. The median age was 56 years, 25.4% were ≥65 years old, 12.7% were Black, 4.0% were Asian, and most patients (80.8%) received care in a community setting. Over half (55.4%) of patients were postmenopausal; 57.9% had an ECOG performance status (PS) 0, while 25.1% had ECOG PS 1. Approximately 33.9% had 1 or more comorbidity and 12.1% had 2 or more comorbidities with diabetes (14.1%) being the most frequent. Most patients had stage II (41.8%) or III (38.4%) disease, nodal status N1 (45.2%) or N2 (35.3%), and tumor grade 2 (52.3%). Abemaciclib was initiated at a median of 11.1 months after early breast cancer diagnosis. Prior to abemaciclib initiation, most patients received radiotherapy (96.3%) and chemotherapy (83.1%), with 46.3% receiving neoadjuvant chemotherapy. Most patients (74.0%) initiated ET 1.6 months prior to abemaciclib initiation. The median time to abemaciclib initiation from breast surgery was 6.7 months. The most frequent regimen was abemaciclib plus aromatase inhibitors (91.0%). At 3 months, 81.6% of patients were persistent; 5.6% resumed abemaciclib after more than 60-day interruption, and 11.3% discontinued due to adverse effects. Additional information on dose modifications will be presented.

Conclusion

In this real-world study of utilization of abemaciclib in the first year after approval for early breast cancer, an older, less fit, and more racially diverse population than participated in the monarchE trial, as well as a higher proportion of patients with lower nodal status was observed. The high 3-month persistence rate suggests abemaciclib for early breast cancer is well tolerated in routine clinical practice.