Quantitative Relationship Between AUEC of Absolute Neutrophil Count and Duration of Severe Neutropenia for G‐CSF in Breast Cancer Patients

The aim of the study was to evaluate the quantitative relationship between duration of severe neutropenia (DSN, the efficacy endpoint) and area under effect curve of absolute neutrophil counts (ANC‐AUEC, the pharmacodynamic endpoint), based on data from filgrastim products, a human granulocyte colony‐stimulating factor (G‐CSF). Clinical data from filgrastim product comparator and test arms of two randomized, parallel‐group, phase III studies in breast cancer patients treated with myelosuppressive chemotherapy were utilized. A zero‐inflated Poisson regression model best described the negative correlation between DSN and ANC‐AUEC. The models predicted that with 10 × 109 day/L of increase in ANC‐AUEC, the mean DSN would decrease from 1.1 days to 0.93 day in Trial 1 and from 1.2 days to 1.0 day in Trial 2. The findings of the analysis provide useful information regarding the relationship between ANC and DSN that can be used for dose selection and optimization of clinical trial design for G‐CSF.