The critical first week following the initiation of chemotherapy1,2


The first 10 days after chemotherapy present the greatest acceleration in risk of hospitalization.4

It takes up to 8 days for pegfilgrastim to accelerate the maturation and proliferation of neutrophil precursors in
bone marrow.5

Patients treated with various chemotherapies may still experience Grade 4 neutropenia between Days 6 and 8, even with the use of pegfilgrastim.5

The Neutropenia Vulnerability Gap occurs within the first 8 days of Cycle 1 when pegfilgrastim monotherapy is least effective.2,5

See below how this gap develops over time – and may result in hospitalizations due to febrile neutropenia (FN), and life-threatening events.6,7


Grade 4 neutropenia develops during the Neutropenia Vulnerability Gap when ANC falls below 0.5 and is associated with:


  1. Crawford J, Dale DC, Lyman GH. Chemotherapy-induced neutropenia: risks, consequences, and new directions for its management. Cancer. 2004;100(2):228-237.
  2. Li Y, Klippel Z, Shih X, Wang H, Reiner M, Page JH. Trajectory of absolute neutrophil counts in patients treated with pegfilgrastim on the day of chemotherapy versus the day after chemotherapy. Cancer Chemother Pharmacol. 2016;77(4):703-712.
  3. Neulasta. Prescribing information. Amgen Inc.; 2021.
  4. Lyman GH, Delgado DJ. Risk and timing of hospitalization for febrile neutropenia in patients receiving CHOP, CHOP-R, or CNOP chemotherapy for intermediate-grade non-Hodgkin lymphoma. Cancer. 2003;98(11):2402-2409.
  5. Burris H, Belani CP, Kaufman PA, et al. Pegfilgrastim on the same day versus next day of chemotherapy in patients with breast cancer, non-small-cell lung cancer, ovarian cancer, and non-Hodgkin’s lymphoma: results of four multicenter, double blind, randomized phase II studies. J Oncol Pract. 2010;6(3):133-140.
  6. Gupta A, Abbasi B, Gupta S. Management of chemotherapy induced neutropenia – an unmet clinical need. Am J Biomed Sci & Res. 2019;4(5):313-318.
  7. NCCN. Clinical Practice Guidelines in Oncology. Hematopoietic Growth Factors, version 2.2020. Accessed May 25, 2021.
  • Mechanism of disease
  • Risk Factors
  • Disease Madnitude
  • Disrupted Outcomes
  • Neutropenia Vulnerability Gap
  • Cost Resource Burden
  • Need for Innovation
  • Resources