(039) Comparing Clinical Outcomes of Abemaciclib in Patients with Hormone Receptor-Positive/HER2-Negative Breast Cancer Filling Through an Internal Specialty Pharmacy versus External Specialty Pharmacies

Poster Abstract:

Background:

Abemaciclib, a selective inhibitor of CDK 4/6, has demonstrated improvements in survival outcomes.1-3 The utilization of abemaciclib has posed substantial challenges for patients due to costs and adverse events such as diarrhea, fatigue, or nausea. These adverse events can impact patient adherence, leading to unsatisfactory treatment outcomes. Various clinical trials have reported abemaciclib discontinuation rates and treatment-related adverse events (TRAEs) with approximately 16% of patients discontinuing due to TRAEs, 52% experiencing treatment interruption due to TRAEs, and 43% requiring dose reductions.4,5 Many patients who discontinued treatment did so without a prior dose adjustment while 74% of patients who received a dose reduction were able to continue treatment without discontinuation.4,5

Objectives:

The primary outcome was to characterize the incidence of discontinuation due to TRAEs and compare them to patients filling at Emory Specialty Pharmacy (ESRx) and outside specialty pharmacies (OSP). Our secondary outcomes included dose adjustments, tolerability, TRAEs, duration of therapy, supportive therapies prescribed, rate of hospitalization, progression-free survival (PFS), and overall survival (OS).

Methods:

Our study is a single-center, retrospective chart review of patients eighteen years or older with HR+/HER2- breast cancer, including both early and advanced stages, receiving abemaciclib from October 1, 2021, to June 1, 2023.

Results:

Eighty-five patients were included in the final analysis with 47 patients filling at ESRx and 38 filling at an OSP. When comparing ESRx and OSP, similar TRAE rates were observed (89.4% vs 89.5%) with 57.4% and 55.2% getting a 1st dose reduction, 14.8% and 26.2% were given a 2nd dose reduction, and 2.1% and 5.3% received a 3rd dose reduction, respectively. Fifty-one percent of dose reductions were due to diarrhea. ESRX had a lower discontinuation rate of 17% vs 23.6% with a mean duration of therapy of 242 days compared to 272 in the ESRx and OSP groups, respectively. Anti-diarrheals were prescribed to 89.3% and 76.3% of patients at ESRx and OSP, respectively. Hospital rates at ESRx were 8.5% compared to 21.1% at OSP, with 1 patient being hospitalized due to abemaciclib that was filling at an OSP. PFS and OS results are pending.

Discussion/

Conclusion:

This study confirmed high rates of dose reductions and discontinuations of abemaciclib. For patients filling at ESRx, lower rates of discontinuation, higher incidence of anti-diarrheals, and lower rates of dose reductions were noted. Patients are followed more closely when filling at ESRx leading to better side effect management and lower rates of discontinuation.

References (must also be included in final poster): 1. Łukasiewicz S, Czeczelewski M, Forma A, et al. Breast Cancer-Epidemiology, Risk Factors, Classification, Prognostic Markers, and Current Treatment Strategies-An Updated Review. Cancers (Basel). 2021 Aug 25;13(17):4287.

2. Wang Y, Minden A. Current Molecular Combination Therapies Used for the Treatment of Breast Cancer. Int J Mol Sci. 2022 Sep 20;23(19):11046.

3. Johnston SRD, Harbeck N, Hegg R; monarchE Committee Members and Investigators. Abemaciclib Combined With Endocrine Therapy for the Adjuvant Treatment of HR+, HER2-, Node-Positive, High-Risk, Early Breast Cancer (monarchE). J Clin Oncol. 2020 Dec 1;38(34):3987-3998.

4. Sledge GW Jr, Toi M, Neven P, et al. MONARCH 2: Abemaciclib in Combination with Fulvestrant in Women With HR+/HER2- Advanced Breast Cancer Who Had Progressed While Receiving Endocrine Therapy. J Clin Oncol. 2017 Sep 1;35(25):2875-2884.

5. Johnston S, Martin M, Di Leo A, et al. MONARCH 3 final PFS: a randomized study of abemaciclib as initial therapy for advanced breast cancer. NPJ Breast Cancer. 2019 Jan 17;5:5.