Results of this real-world study demonstrated that the impact of abemaciclib complements the pivotal clinical trial data.
Abemaciclib is the oral CDK4/6 inhibitor that received US Food and Drug Administration approval most recently. Abemaciclib treats hormone receptor–positive, HER2-negative advanced or metastatic breast cancer. Kimberly R. Saverno, PhD, RPh, Senior Research Scientist, Eli Lilly and Company, Indianapolis, IN, and colleagues analyzed administrative claims data to define patient characteristics, evaluate outcomes, and assess patterns in real-world utilization, in a US patient cohort upon initiating abemaciclib therapy for the treatment of hormone receptor–positive, HER2-negative metastatic breast cancer.
In this retrospective observational study, medical and pharmacy claims were analyzed from adult patients who were newly initiating abemaciclib therapy between September 2017 and October 2019.
Patients were included in the study if they had ≥2 secondary neoplasm diagnoses, evidence of hormone receptor–positive disease, ≥2 breast cancer diagnoses, continuous enrollment ≥6 months before and ≥90 days after abemaciclib initiation (index date), and absence of therapies suggesting HER2-positive disease.
Grouping was completed according to concomitant therapy (aromatase inhibitor, fulvestrant, 200-mg abemaciclib monotherapy, or other), and stratification based on previous CDK4/6 inhibitor use.
From this data set, reason for discontinuation and line of therapy were indeterminable.
Time to discontinuation was defined as a gap of 60 days without an abemaciclib fill, following exhaustion of days’ supply from previous fills or initiation of a different CDK4/6 inhibitor (ie, palbociclib or ribociclib). In total, 454 patients were included in the study (mean age, 57.7 years [standard deviation, 10.8]; 98.9% female). New abemaciclib initiator prevalence was 35.0% (N = 159) in the fulvestrant group, 10.4% (N = 47) in the 200-mg abemaciclib monotherapy group, 29.3% (N = 133) in the aromatase inhibitor group, and 25.3% (N = 115) in the other group. Previous CDK4/6 inhibitor use within each regimen ranged from 37.6% (aromatase inhibitor) to 60.0% (other).
Visceral metastases were recorded in 50.4% of the aromatase inhibitor group; 49.7% of the fulvestrant group; 55.3% of the 200-mg abemaciclib monotherapy group; and 47.8% of the other group. Approximately 75% (N = 331) of all abemaciclib initiators started treatment with a 150-mg dose. In the 6-month preindex period, chemotherapy use was observed for 18.8% in the aromatase inhibitor group; 21.4% in the fulvestrant group; 51.1% in the 200-mg abemaciclib monotherapy group; and 21.7% in the other group. The median length of follow-up for all abemaciclib initiators was 321 days (interquartile range, 195-482).
Of those patients without a previous history of CDK4/6 inhibitor use, the median time to discontinuation for the fulvestrant group was 531 days (95% confidence interval [CI], 281-not reached [NR]), the 200-mg abemaciclib monotherapy group was 141 days (95% CI, 80-NR), the aromatase inhibitor group was NR (95% CI, 430-NR), and the other group was 392 days (95% CI, 300-NR). In the subset of previous CDK4/6 inhibitor use patients, the median time to discontinuation for the fulvestrant group was 146 days (95% CI, 93-225), the 200-mg abemaciclib monotherapy group was 140 days (95% CI, 86-NR), the aromatase inhibitor group was 196 days (95% CI, 125-NR), and the other group was 191 days (95% CI, 113-280).
The investigators concluded that by complementing the pivotal abemaciclib clinical trial results, these real-world data help to expand understanding by examining abemaciclib use among a more heterogeneous population of patients in a clinical practice setting. The considerable number of patients with previous CDK4/6 inhibitor use, visceral metastases, and previous chemotherapy at the time of initiating abemaciclib therapy suggests many patients had very advanced disease and/or were in later stages of their treatment continuum.
There were limitations to the study, insofar as claims data lack many variables of clinical relevance needed to fully understand disease severity in the study population, such as line of therapy and degree of endocrine sensitivity. Therefore, these limits should be considered when interpreting and contextualizing CDK4/6 inhibitor administrative claims studies.
Source: Saverno KR, Beyrer J, Nash Smyth E, et al. Real-world patient characteristics, utilization patterns, and outcomes of US patients with HR+/HER2- metastatic breast cancer treated with abemaciclib. Presented at: 2020 San Antonio Breast Cancer Symposium, December 8-11, 2020. Abstract PS10-46.
