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Medically reviewed by C.H. Weaver M.D. Medical Editor 6/2021

A low white blood cell count or “neutropenia” is a condition characterized by abnormally low levels of neutrophils in the circulating blood. Neutrophils are a specific kind of white blood cell that help prevent and fight infections. The most common reason that cancer patients experience neutropenia is as a side effect of chemotherapy. Chemotherapy-induced neutropenia increases a patient’s risk of infection and disrupts cancer treatment. Fortunately, neutropenia can be prevented through the use of white blood cell growth factors. The prevention of neutropenia allows patients to receive their scheduled treatment and reduces the risk of infection and hospitalization.1-8

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What is neutropenia

Neutropenia is a condition characterized by abnormally low blood levels of infection-fighting neutrophils, a specific kind of white blood cell. Neutropenia increases your risk of bacterial and fungal infections.

The most common reason that cancer patients experience neutropenia is as a side effect of chemotherapy. Chemotherapy involves the use of drugs to destroy cancer cells. Chemotherapy works by destroying cells that grow rapidly, a characteristic of cancer cells. Unfortunately, chemotherapy also affects normal cells that grow rapidly, such as blood cells in the bone marrow, cells in the hair follicles, or cells in the mouth and intestines. Chemotherapy-induced neutropenia typically occurs 3-7 days following administration of chemotherapy and continues for several days before neutrophil levels return to normal. The type and dose of chemotherapy affects how low the neutrophil count drops and how long it will take to recover.

Infrequently, cancer patients may also experience neutropenia from other medications or as a consequence of their underlying cancer. When discussing the consequences and management of neutropenia, it is important to distinguish between chemotherapy-induced neutropenia and neutropenia resulting from other causes because they may be managed differently.

While receiving chemotherapy, you will frequently have your complete blood count (CBC) checked to determine whether you have enough neutrophils. Typically there are billions of neutrophils in the blood; however, certain chemotherapy drugs will lower the neutrophil count. When a doctor or nurse discusses CBC test results, they frequently refer to the “absolute neutrophil count” (ANC) or the number of neutrophils in the patient’s blood. A “low white blood count” is another common term used to describe a low neutrophil level in the blood. Fortunately, having a low level of neutrophils can be corrected.

Why is chemotherapy induced neutropenia important?

Chemotherapy-induced neutropenia is important because it may:

  • Increase your risk of life-threatening infection.
  • Disrupt delivery of your cancer treatment, resulting in a change to the planned dose and time.

The fewer the neutrophils in the blood and the longer you remain without enough neutrophils, the more susceptible you are to developing a bacterial or fungal infection. Neutrophils are a major component of antibacterial defense mechanisms. As the neutrophil count falls below 1.0, 0.5, and 0.1 x 109/L, the frequency of life-threatening infection rises steeply from 10% to 19% and 28%, respectively. If you develop a fever during neutropenia you may require treatment with intravenous antibiotics and admission to the hospital until the number of neutrophils in the blood returns to sufficient levels to fight the infection.

Another reason neutropenia is important is that, in some cases, it can be severe enough that your chemotherapy treatment may need to be delayed or dose reduced, which reduces some patients’ chance for cure. When you are treated with chemotherapy, it is for the purpose of destroying cancer cells in order to reduce symptoms from your cancer, prolong your survival or increase your chance of cure. The dose and time schedule of chemotherapy drugs administered have been scientifically determined to produce the best chance of survival or cure. If you develop neutropenia, your doctors may have to delay your treatment or reduce the doses of your chemotherapy until your neutrophil counts have recovered. 

Clinical studies have shown that, for certain cancers, reducing the dose of chemotherapy or lengthening the time between treatments lowers cure rates compared to full-dose, on-time treatment. Fortunately, there are strategies for the prevention of chemotherapy-induced neutropenia that have been proven to reduce the incidence of fever, infection, admission to the hospital and allow you to receive your treatment on schedule.

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Who is at a higher risk for chemotherapy induced neutropenia?

  • Patients receiving chemotherapy that decreases the number of white blood cells
  • Patients who already have a low white blood cell count, or who have previously received chemotherapy or radiation treatment
  • Patients age 70 and older who may be at risk of more severe infection and longer hospitalizations
  • Patients with other conditions affecting their immune system

Can neutropenia be prevented?

Chemotherapy-induced neutropenia can be prevented in most patients with the use of white blood cell growth factors. Blood cell growth factors are naturally occurring substances called cytokines that regulate certain critical functions in the body. They are responsible for stimulating cells in the bone marrow to produce more blood cells.

The white blood cell growth factors approved by the U.S. Food and Drug Administration for the prevention of chemotherapy-induced neutropenia are Neupogen® (filgrastim) and Neulasta® (pegfilgrastim).

Chemotherapy for Older Patients: What You Should Know About the Risk of Infection

As you may already know, chemotherapy works by attacking the rapidly dividing cells it finds in the body, particularly cancer cells because they multiply quickly. However, chemotherapy can’t differentiate between cancer cells and other rapidly dividing healthy cells, such as bone marrow cells. As a consequence, many chemotherapy patients, especially older patients, experience a drop in the levels of their blood cells, including their infection-fighting white blood cells.1,3,4 This may lead to the patient’s chemotherapy being stopped or reduced until the white blood cell count recovers enough to resume treatment, which can give cancer cells a chance to grow. A low white blood cell count, a condition called neutropenia, may also increase a patient’s risk of infection, which can lead to delays in treatment, or hospitalization.1,4,5,6

Chemotherapy-related infections may:

  • Delay chemotherapy treatment
  • Require changing the patient’s chemotherapy dose
  • Require hospitalization, most commonly in the first and second chemotherapy cycles.5,7

Older patients, due to normal body changes, are at greater risk than younger patients for a low white blood cell count and its complications.1,4 For example, the risk of infection is measurably greater in patients receiving chemotherapy with non-Hodgkin’s lymphoma aged 65 and older than in younger patients. Not only are these complications more common in older patients, but when older patients are hospitalized to treat an infection, they tend to have longer hospital stays than younger patients.1,4,6

To help minimize the risk of such complications, older patients are more likely than younger patients to be given reduced doses of chemotherapy. However, studies indicate that full-dose, on-schedule treatments may improve outcomes, especially in the case of potentially curable tumors. This is important to know because older patients with cancer can respond as well to treatment as younger patients if they are given similar levels of chemotherapy.1,3

Fortunately, there are drugs called white blood cell boosters that can stimulate white blood cell production and help protect against infection caused by strong chemotherapy, and may help allow full-dose chemotherapy on schedule.1,4,6,

General PMF Newsletter 490


  1. Repetto L. Greater risks of chemotherapy toxicity in elderly patients with cancer. J Supportive Oncol. 2003;1(2):18-24.
  2. Chemotherapy and you: A Guide to self-help during cancer treatment: Understanding chemotherapy. National Cancer Institute Web site. Available at: herapy-and-you/page2. Accessed December 8, 2004.
  3. Older patients with colon cancer benefit from chemotherapy. National Cancer Institute Web site. Available at: . Accessed December 8, 2004.
  4. Osby E, Hagberg H, Kvaloy S, et al. CHOP is superior to CNOP in elderly patients with aggressive lymphoma while outcome is unaffected by Filgrastim treatment: results of a Nordic Lymphoma Group randomized trial. Blood. 2003 May 15;101(10):3840-8.
  5. 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 Dec 1;98(11):2402-9.
  6. Rivera E, Erder MH, Fridman M, Frye D, Hortobagyi GN. First-cycle absolute neutrophil count can be used to improve chemotherapy-dose delivery and reduce the risk of febrile neutropenia in patients receiving adjuvant therapy: a validation study. Breast Cancer Res. 2003;5(5):R114-R120.
  7. Lyman GH, Morrison VA, Dale DC, Crawford J, Delgado DJ, Fridman M; OPPS Working Group; ANC Study Group. Risk of febrile neutropenia among patients with intermediate-grade non-Hodgkin’s lymphoma receiving CHOP chemotherapy. Leuk Lymphoma. 2003 Dec;44(12):2069-76.
  8. Neulasta® (pegfilgrastim) prescribing information, Amgen.