(200) Real-World Analysis of Adjuvant Abemaciclib in High-Risk HR+/HER2- Early-Stage Breast Cancer

Poster Abstract: Background
In hormone receptor positive (HR+) early-stage breast cancer, guidelines recommend patients receive endocrine therapy (ET) after primary treatment to reduce the risk of relapse or recurrence. Despite appropriate ET, up to 30% of patients may still experience disease recurrence in the first 10 years, often with distant metastases. This sparks a critical need to optimize adjuvant therapy. In monarchE, an open-label, randomized, phase 3 trial, the combination of abemaciclib for 2 years with standard of care ET demonstrated improved invasive disease-free survival and distant relapse-free survival when compared to standard of care ET alone. However, this also came with a significant increase in adverse effects, which led to 62% of patients requiring treatment interruptions and 44% requiring dose reductions. Additionally, use of abemaciclib requires frequent monitoring for toxicities leading to increased patient burden and clinic workloads. Further studies are needed to assess adjuvant systemic therapies to better individualize CDK4/6 inhibitor therapy.

Objective:
The purpose of this study is to describe patient demographics and cancer characteristics of early-stage breast cancer patients on adjuvant abemaciclib with ET and provide real-world data of the patient experience throughout their treatment course of abemaciclib.

Methods
A retrospective chart analysis will be conducted on all patients who initiated adjuvant abemaciclib under the care of an OhioHealth physician between October 1, 2021 to September 30, 2022. Patients with metastatic disease, other cancers, history of treatment with any other CDK4/6 inhibitor, and pregnant/breastfeeding females will be excluded from this study. Data will be collected until discontinuation of abemaciclib or October 1, 2023; whichever comes first. Patient demographics, prior chemotherapy, and ET will be recorded. Additionally, adverse events (e.g., diarrhea, myelosuppression, transaminitis, etc.), dose adjustments, drug holidays, treatment discontinuations, and duration of therapy will be documented. Although not an aim for this study, disease progression or disease recurrence will be recorded, if available.

Conclusions of this study are not yet available but will be presented at Hematology/Oncology Pharmacy Association 2024 Annual Conference April 3-6, 2024

References (must also be included in final poster): [1] Early Breast Cancer Trialists’ Collaborative Group (EBCTCG): Aromatase inhibitors versus tamoxifen in early breast cancer: Patient-level meta-analysis of the randomized trials. Lancet 386:1341-1352, 2015

[2] Johnston, Stephen R. D., Masakazu Toi, Joyce O’Shaughnessy, Priya Rastogi, Mario Campone, Patrick Neven, Chiun-Sheng Huang, et al. 2023. “Abemaciclib plus Endocrine Therapy for Hormone Receptor-Positive, HER2-Negative, Node-Positive, High-Risk Early Breast Cancer (monarchE): Results from a Preplanned Interim Analysis of a Randomised, Open-Label, Phase 3 Trial.” The Lancet Oncology 24 (1): 77–90.