Clinical utility of immature granulocyte monitoring for optimizing g-CSF use during chemotherapy-induced neutropenia

Introduction: Prolonged neutropenia is a major complication of chemotherapy-induced neutropenia in hematologic malignancies, often leading to empirical and prolonged use of granulocyte colony-stimulating factors (G-CSF). Immature granulocytes (IG) have recently been proposed as a surrogate marker of bone marrow recovery. Objectives: This study aimed to evaluate the prognostic value of IG kinetics for neutropenia resolution and to explore its potential role in optimizing supportive pharmacotherapy. Method: A retrospective cohort of adult patients with hematologic malignancies treated between 2022 and 2024 was analyzed. Serial IG counts were extracted from automated complete blood counts during neutropenic episodes. Chemotherapy regimens were classified by myelosuppressive intensity, and subgroup analyses were conducted according to malignancy subtype and G-CSF administration. Temporal associations between IG elevation and absolute neutrophil count (ANC) recovery were examined, and predictive accuracy was assessed using ROC analysis. Results: Forty-five patients (mean age: 62.6 ± 14.2 years; 67% male) were included, of whom 82% had lymphoproliferative disorders. The median duration of neutropenia was 6 days (IQR: 3–12), shorter among those receiving G-CSF and with lymphoid malignancies. IG elevation significantly preceded or coincided with ANC recovery (median lag: 0 days) and showed high predictive accuracy (AUC: 0.91–0.98). Conclusion: IG kinetics were predictive of neutropenia recovery and may serve as an early, low-cost biomarker to guide the discontinuation or de-escalation of G-CSF. Integrating IG monitoring into clinical decision-making could improve supportive pharmacotherapy in patients with chemotherapy-induced neutropenia.