Noteworthy Numbers: Neutropenia

Neutropenia is characterized by low levels of neutrophils, the white blood cells that fight infections. In general, the condition is defined as an absolute neutrophil count (ANC) <1500/μL.¹ There are several factors that can contribute to the development of neutropenia, including idiopathic and congenital etiologies, as well as some cancers, such as leukemia, myeloma, and lymphoma.¹ However, one of the most common causes of neutropenia is the use of chemotherapy.^1,2 The following provides a brief look at some of the key statistics regarding this condition.

Each year in the United States, approximately 650,000 patients with cancer will be treated with chemotherapy in the outpatient setting, and approximately 50% of these patients will develop some level of neutropenia.^2,3 This condition is the most serious hematologic toxicity of chemotherapy, often leading to dose reductions or delays.³

Neutropenia can be classified as mild, moderate, or severe, depending on the number of neutrophils present in a patient’s blood sample¹:

• Mild neutropenia: ANC 1000-1500 cells/µL
• Moderate neutropenia: 500-1000 cells/µL
• Severe neutropenia: <500 cells/µL.

Patients aged >70 years who are diagnosed with cancer and those who have undergone organ transplantation are at an increased risk for developing neutropenia.^2,4

Fever is a common manifestation of chemotherapy-induced neutropenia, occurring in 10% to 50% of patients with solid tumors and >80% of those with blood cancers.⁴ It is estimated that febrile neutropenia (FN) occurs in >50% of patients within their first cycle of chemotherapy.⁵ The rate of major complications in patients with FN is approximately 25% to 30%, with mortality as high as 11%.⁶ The mortality rate in patients who progress to severe sepsis or septic shock can be as high as 50%.⁶

In 2018, the American Society of Clinical Oncology and the Infectious Diseases Society of America updated their clinical practice guideline for the outpatient management of FN in patients with cancer. The guideline recommends starting initial doses of empirical antibacterial therapy within 1 hour of triage and monitoring for ≥4 hours in patients with FN. Patients who do not defervesce after 2 to 3 days should be re-evaluated and considered for inpatient treatment. The panel stressed the importance of clinical judgment when determining which patients are candidates for outpatient management using clinical criteria or a validated tool such as the Multinational Association of Support Care in Cancer risk index.⁶

References

1. Territo M. Neutropenia. Updated January 2020. www.merckmanuals.com/professional/hematology-and-oncology/leukopenias/neutropenia#. Accessed March 4, 2021.
2. Cancer.net. Neutropenia. September 2019. www.cancer.net/coping-with-cancer/physical-emotional-and-social-effects-cancer/managing-physical-side-effects/neutropenia#:~:text=Half%20of%20people%20with%20cancer,kill%20organisms%20that%20cause%20infection. Accessed March 4, 2021.
3. Centers for Disease Control and Prevention. Preventing infections in cancer patients. November 10, 2020. www.cdc.gov/cancer/preventinfections/. Accessed March 4, 2021.
4. Braden CD. Neutropenia. Updated November 5, 2020. https://emedicine.medscape.com/article/204821-print. Accessed March 4, 2021.
5. Crawford J, Dale DC, Kuderer NM, et al. Risk and timing of neutropenic events in adult cancer patients receiving chemotherapy: the results of a prospective nationwide study of oncology practice. J Natl Compr Canc Netw. 2008;6:109-118.
6. Taplitz RA, Kennedy EB, Bow EJ, et al. Outpatient management of fever and neutropenia in adults treated for malignancy: American Society of Clinical Oncology and Infectious Diseases Society of America clinical practice guideline update. J Clin Oncol. 2018;36:1443-1453.