Incidence of Neutropenia Adverse Events Identified in Electronic Healthcare Records Among Initiators of CDK4/6 Inhibitors With Advanced Breast Cancer in the UK
Author(s)
Lockwood Taylor, PhD, MPH1, Elsie Horne, PhD2, Patrycja Pluta, DVM, PhD3, Amit Samani, MD, PhD2, Qianyi Zhang, MS1, Sascha van Boemmel-Wegmann, PhD3, Blythe Adamson, PhD, MPH1.
1Flatiron Health, New York, NY, USA, 2Flatiron Health UK, London, United Kingdom, 3Flatiron Health Germany, Berlin, Germany.
1Flatiron Health, New York, NY, USA, 2Flatiron Health UK, London, United Kingdom, 3Flatiron Health Germany, Berlin, Germany.
OBJECTIVES: A precursor to targeted safety surveillance is ensuring that underlying electronic health record (EHR) data are relevant and reliable. Lab-based adverse events (AEs) may be identified from structured data in the EHR. The purpose of this study is to assess rates of neutropenia AEs derived from structured EHR lab data among CDK4/6 inhibitor (CDK4/6i)-treated women with advanced breast cancer in the UK.
METHODS: This retrospective cohort study leveraged EHR data from the UK Flatiron Health Research Database (FHRD). The real-world cohort consisted of women who initiated CDK4/6is for locally advanced or metastatic hormone receptor-positive and human epidermal growth factor receptor 2-negative breast cancer on or after January 1, 2017. Patients were required to have a full blood count in the 4 weeks before treatment initiation. Neutropenia was defined based on absolute neutrophil count of <1500 cells/µL. AE grade for neutropenia (cells/µL) was categorized as follows: grade 2, 1500-1000; grade 3, <1000-500; grade 4, <500. Cumulative incidence of neutropenia AEs was calculated.
RESULTS: A total of 147 women met study eligibility criteria. The median age at treatment initiation was 57 years. Overall, 88% women were white, 90% had an ECOG score of ≤1, and the most commonly-initiated CDK4/6is were palbociclib (62%) and ribociclib (39%). During the first 16 weeks of treatment, grade 2, 3, and 4 neutropenia AEs were identified in 98, 59, and <10 patients, respectively. The 30-day and 90-day cumulative incidence (95% CI) of first AE occurrence was 64% (56%-71%) and 70% (61%-77%) for grade 2+, and 38% (29%-45%) and 40% (32%-48%) for grade 3+, respectively.
CONCLUSIONS: The occurrence of neutropenia among CDK4/6i initiators in the UK FHRD is consistent with previously reported studies. Observed results lay the foundation for the development and implementation of a safety surveillance system for lab-based AEs.
METHODS: This retrospective cohort study leveraged EHR data from the UK Flatiron Health Research Database (FHRD). The real-world cohort consisted of women who initiated CDK4/6is for locally advanced or metastatic hormone receptor-positive and human epidermal growth factor receptor 2-negative breast cancer on or after January 1, 2017. Patients were required to have a full blood count in the 4 weeks before treatment initiation. Neutropenia was defined based on absolute neutrophil count of <1500 cells/µL. AE grade for neutropenia (cells/µL) was categorized as follows: grade 2, 1500-1000; grade 3, <1000-500; grade 4, <500. Cumulative incidence of neutropenia AEs was calculated.
RESULTS: A total of 147 women met study eligibility criteria. The median age at treatment initiation was 57 years. Overall, 88% women were white, 90% had an ECOG score of ≤1, and the most commonly-initiated CDK4/6is were palbociclib (62%) and ribociclib (39%). During the first 16 weeks of treatment, grade 2, 3, and 4 neutropenia AEs were identified in 98, 59, and <10 patients, respectively. The 30-day and 90-day cumulative incidence (95% CI) of first AE occurrence was 64% (56%-71%) and 70% (61%-77%) for grade 2+, and 38% (29%-45%) and 40% (32%-48%) for grade 3+, respectively.
CONCLUSIONS: The occurrence of neutropenia among CDK4/6i initiators in the UK FHRD is consistent with previously reported studies. Observed results lay the foundation for the development and implementation of a safety surveillance system for lab-based AEs.
Conference/Value in Health Info
2025-11, ISPOR Europe 2025, Glasgow, Scotland
Value in Health, Volume 28, Issue S2
Code
EPH143
Topic
Epidemiology & Public Health
Topic Subcategory
Safety & Pharmacoepidemiology
Disease
Oncology