Editor’s Note: Based on the results of the monarchE trial, abemaciclib combined with endocrine therapy (ET) has become the standard adjuvant treatment for patients with high-risk HR+/HER2− early breast cancer (EBC). However, systematic data regarding its use in routine Chinese clinical practice have remained limited.At the ESMO Breast Cancer Congress 2026 (ESMO BC 2026), the team led by Academician Binghe Xu from the Cancer Hospital, Chinese Academy of Medical Sciences, presented a large-scale real-world study based on the National Cancer Center database (Abstract No. 224eP). The study included 2,944 patients and systematically characterized patient demographics, treatment patterns, and treatment persistence among Chinese patients receiving adjuvant abemaciclib.
The findings showed that most patients initiated treatment at the standard dose, while the 12-month treatment persistence rate reached 93.8%, suggesting that abemaciclib is being used in a standardized manner with favorable tolerability in real-world Chinese clinical practice. Oncology Frontier invited Professor Jiayu Wang, first author of the study from the Cancer Hospital, Chinese Academy of Medical Sciences, to provide further insight into the study and its clinical implications.
Study Overview
Background
Following the monarchE trial, adjuvant abemaciclib plus endocrine therapy was approved for patients with high-risk HR+/HER2− early breast cancer. However, real-world evidence regarding patient characteristics, treatment patterns, and treatment persistence in Chinese clinical practice has remained scarce.
This study aimed to characterize the real-world use of adjuvant abemaciclib during the first two years after its approval by China’s National Medical Products Administration (NMPA) in December 2021, with the goal of providing practical insights for routine clinical care in China.
Study Design
This retrospective cohort study utilized electronic medical record data from the National Cancer Center (NCC) database. Eligible patients were adults with stage I–III HR+/HER2− early breast cancer who initiated adjuvant abemaciclib between January 1, 2022 and December 31, 2023. Patients who had previously received abemaciclib within an EBC clinical trial were excluded.
The index date was defined as the date of the first abemaciclib prescription during the screening period. Follow-up continued through June 30, 2024, and only patients with at least six months of observable follow-up were included in the final analysis.
Patient characteristics and treatment patterns were analyzed descriptively, while treatment persistence was estimated using Kaplan–Meier analysis.
Study Results
Baseline Characteristics
A total of 2,944 patients were included in the study. The majority had node-positive disease (94.9%), and 61.1% had four or more positive lymph nodes. Nearly all patients (97.9%) had stage II or III disease.
The mean age was 49.1 years (SD 11.1), and the cohort included a slightly higher proportion of premenopausal patients compared with postmenopausal patients (53.1% vs 46.9%). Importantly, 87.4% of patients met the high-risk criteria defined in the monarchE trial, suggesting that patient selection in routine Chinese practice closely aligns with established indications.
Treatment Patterns
Nearly half of the patients (47.6%) had received prior neoadjuvant therapy. Almost all patients underwent neoadjuvant or adjuvant chemotherapy (97.9%), while 78.2% also received radiotherapy.
Prior use of CDK4/6 inhibitors during the neoadjuvant setting was uncommon, occurring in only 2.5% of patients, with abemaciclib accounting for the majority of these cases. Likewise, switching to or using alternative CDK4/6 inhibitors before or after adjuvant abemaciclib was rare.
Most patients (80.5%) initiated abemaciclib at the standard dose of 150 mg twice daily. Among those who started at this dose, 86.3% maintained the original dose throughout treatment, while only a minority required dose adjustments, most commonly to 100 mg twice daily.
A smaller proportion of patients (14.1%) started at 100 mg twice daily. Notably, among patients initiating at the lower dose, the majority were eventually able to escalate to the standard 150 mg twice-daily dose, suggesting that dose escalation may be feasible for many patients initially considered vulnerable to toxicity.
Regarding endocrine therapy combinations, 92.2% of patients received aromatase inhibitors, and more than half of these patients also received ovarian function suppression (OFS). This treatment pattern reflects the relatively young age and high proportion of premenopausal women within the Chinese patient population.
The median interval from surgery to initiation of abemaciclib was 181 days, and 93.8% of patients began abemaciclib within 16 months after surgery. The median interval between initiation of endocrine therapy and addition of abemaciclib was 31 days, with 68.5% of patients starting abemaciclib within 12 weeks after endocrine therapy initiation.
Treatment Persistence and Tolerability
One of the most notable findings of the study was the high treatment persistence rate observed in real-world practice. Persistence remained consistently high over time, declining only slightly from 96.7% at 3 months to 93.8% at 12 months.
Age-stratified analyses revealed somewhat lower persistence among older patients. Patients younger than 60 years had a 12-month persistence rate of 95.0%, compared with 87.7% among patients aged 60 years or older.
During a median follow-up of 13.2 months, only 123 patients (4.2%) discontinued abemaciclib. The most common reason for discontinuation was treatment intolerance, accounting for 65.0% of discontinuations, followed by disease recurrence and other or unspecified reasons.
Switching to another CDK4/6 inhibitor during adjuvant therapy was uncommon. Among the small number of patients who switched therapies, subsequent discontinuation rates appeared somewhat higher than among patients who remained on abemaciclib.
Overall, the relatively low discontinuation rate suggests that abemaciclib demonstrates favorable tolerability in routine Chinese clinical practice for early breast cancer.
Study Conclusions
This study represents the largest real-world analysis to date evaluating adjuvant abemaciclib use among Chinese patients with early breast cancer.
The findings demonstrate that most patients are treated according to standard monarchE-based practice patterns, with the majority initiating therapy at the recommended 150 mg twice-daily dose and maintaining treatment over time. Treatment persistence remained remarkably high at both 6 and 12 months, while discontinuation rates were low, supporting the real-world feasibility and tolerability of adjuvant abemaciclib in Chinese clinical settings.
However, the investigators cautioned that the relatively short median follow-up duration of 13 months limits interpretation of long-term treatment persistence and completion of the full 2-year adjuvant treatment course.
Investigator Commentary
Professor Jiayu Wang emphasized that this study fills an important gap in real-world evidence for Chinese patients following the pivotal monarchE trial. She noted that the cohort reflects several distinct characteristics of the Chinese population, including younger patient age and a higher proportion of premenopausal women compared with Western clinical trial populations.
According to Professor Jiayu Wang, these demographic differences are clinically meaningful because younger patients often require clinicians to balance antitumor efficacy with fertility preservation and long-term quality-of-life considerations.
She also highlighted the high level of adherence to guideline-based treatment strategies in China. Most patients received the standard abemaciclib plus endocrine therapy regimen, and the extensive use of OFS appropriately reflected the younger age distribution of the cohort.
Professor Jiayu Wang considered the dose-adjustment findings particularly informative for routine clinical management. The fact that many patients who started at lower doses were later able to escalate successfully to the standard dose suggests that individualized dose optimization strategies may improve treatment tolerability without compromising long-term treatment goals.
She further noted that the exceptionally high 12-month persistence rate observed in this study may reflect the strong motivation associated with curative-intent adjuvant therapy. Nevertheless, the lower persistence observed among older patients highlights the importance of proactive toxicity management, individualized dosing strategies, and multidisciplinary patient support.
Finally, Professor Jiayu Wang emphasized that longer follow-up will be necessary to fully evaluate completion rates for the standard two-year treatment duration and to better understand the long-term clinical benefits of adjuvant abemaciclib in real-world Chinese practice.
Professor Jiayu Wang
