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. 2021 Jun;21(3):205-209.
doi: 10.1016/j.clbc.2020.09.010. Epub 2020 Oct 2.

Real-world Outcomes of Cyclin-dependent Kinase Inhibitors Continued Beyond First Disease Progression in Hormone Receptor-positive Metastatic Breast Cancer

Akaolisa Samuel Eziokwu  1 , Leticia Varella  2 , Megan Lynn Kruse  2 , Xuefei Jia  2 , Halle C F Moore  2 , George Thomas Budd  2 , Jame Abraham  2 , Alberto J Montero  2
Affiliations

Real-world Outcomes of Cyclin-dependent Kinase Inhibitors Continued Beyond First Disease Progression in Hormone Receptor-positive Metastatic Breast Cancer

Akaolisa Samuel Eziokwu et al. Clin Breast Cancer. 2021 Jun.

Abstract

Background: CDK4/6 inhibitors (CDK4/6i), in combination with aromatase inhibitors, are United States Food and Drug Administration-approved for the treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). The effectiveness of continuing them beyond first disease progression (PD) is currently unknown. This retrospective study evaluated the impact of the continuation of CDK4/6i beyond first PD in HR+/HER2- MBC using real-world experience.

Patients and methods: A single-institution retrospective review of patients with HR+ MBC who received CDK4/6is from 2015 to 2018 and where CDK4/6is were continued beyond first PD. The primary outcome was progression-free survival (PFS) after initial PD on CDK4/6i therapy.

Results: Thirty women with HR+/HER2- MBC met eligibility criteria. Patients were identified from a prospective database of patients at the Cleveland Clinic Foundation who were prescribed CDK4/6is. The median age and follow-up duration were 47.5 years and 27 months, respectively. Most patients received palbociclib (PA)/letrozole as initial therapy (67%), followed by PA/fulvestrant (23%), and PA/other aromatase inhibitor (20%), and abemaciclib with either fulvestrant or letrozole (6%). As of January 31, 2019, 25 (83.3%) patients were still alive, and 19 (63%) patients had progressed. The estimated median PFS for continued CDK4/6i use beyond the first PD was 11.8 months (95% confidence interval, 5.34-13.13 months).

Conclusions: Among a small cohort of patients with HR+ MBC in a non-clinical trial setting, continuation of CDK4/6i-endocrine treatment post initial PD was associated with a median PFS of about 12 months. Formal randomized clinical trials evaluating the continuation of CDK4/6is beyond the first PD are currently ongoing and will provide more answers to this important clinical question.

Keywords: Abemaciclib; Endocrine therapy; Fulvestrant; Letrozole; Palbociclib.

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