Studying the Real-World UK Multicenter Experience with Abemaciclib and Endocrine Therapy for Hormone Receptor–Positive, HER2-Negative Advanced Breast Cancer

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For hormone receptor (HR)-positive, HER2-negative advanced breast cancer, abemaciclib is approved in both the first- and second-line treatment settings. In the real world, however, outcomes remain uncertain.

To ascertain the efficacy and safety profile of abemaciclib among 15 institutions in the United Kingdom, Battisti and colleagues retrospectively, between July 2018 and June 2020, identified patients with HR-positive, HER2-negative advanced breast cancer who received treatment with abemaciclib.

The investigators collected a comprehensive range of baseline information, including blood tests, demographics, disease characteristics, prior treatments, toxicities, and treatment delays and responses.

The 228 total patients who were identified had a median age of 64 years (range, 31-93 years). Approximately three-quarters (75.4%) of patients were postmenopausal and 91.7% had Eastern Cooperative Oncology Group performance status 0-1. Nearly two-thirds (63.6%) of patients had visceral involvement and 19.3% only had bone disease.

In the study, patients received a median of 1 (range, 0-7) prior line of treatment and 0 (range, 0-5) prior chemotherapy lines. The researchers also reported on adverse events. Nearly two-thirds (64.9%) of patients experienced diarrhea (grade ≥3 in 7.0%).

In addition, 64.0% of patients developed neutropenia (grade ≥3 in 17.5%). Febrile neutropenia was experienced by 2.2% of patients. As a result of toxicity, 14.0% of patients required hospitalization.

Dose reductions were required in nearly half (46.9%) of patients, primarily owing to diarrhea in nearly one-quarter (24.1%) of patients; this reduction was to a level of 50 mg twice per day in 13.2% of patients. Dose delays occurred in a median of 14 days (range, 2-118 days).

Discontinuation of abemaciclib occurred in 53.1%, generally based on progression of disease (26.7%), and toxicity (21.0%) or diarrhea (7.0%).

In the 163 patients assessed, abemaciclib produced a clinical benefit rate of 82.8% and an overall response rate of 47.2%. The median overall survival was 8.8 months, and median progression-free survival was 6.4 months.

The safety and efficacy of abemaciclib in combination with endocrine therapy for advanced HR-positive breast cancer was part of the large real-world analysis. In this analysis, compared with the pivotal trial data, the rates of diarrhea were lower while the rates of neutropenia were higher.

In this cohort, the median overall survival was worse, which may reflect the different population of patients included, who were older and had more frequent visceral involvement despite the progression-free survival outcomes were similar to those previously reported.

The investigators concluded that to ensure adequate efficacy and safety outcomes, the selection of patients suitable for abemaciclib is crucial.


Battisti NML, Morrison L, Nash T, et al. Abemaciclib and endocrine therapy for hormone receptor-positive, HER2-negative advanced breast cancer: a real-world UK multicentre experience. 2021 San Antonio Breast Cancer Symposium; December 7-10, 2021. P1-17-08.

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