Weycker, D., Li, X., Barron, R., Li, Y., Reiner, M., Kartashov, A., . . . Garcia, J. (2016). Risk of chemotherapy-induced febrile neutropenia with early discontinuation of pegfilgrastim prophylaxis in US clinical practice. Supportive Care in Cancer, 24, 2481–2490. 

To investigate the receipt of colony-stimulating factor (CSF) prophylaxis and associated risks of febrile neutropenia (FN)

Data from two large U.S. claims repositories from 2006–2014 were obtained for analysis. Data included patients aged older than 18 years who received at least two cycles of myelosuppressive chemotherapy. The analysis was focused on the use of pegfilgrastim; patients who received other CSFs were excluded from the analysis. Patients who received and did not receive pegfilgrastim prophylaxis were matched according to variables in multivariate regression, including the being at intermediate/high risk for neutropenia and cancer type.

• N = 42,314   
• MEAN AGE = 54.6 years (SD = 10.7)
• MALES: 10.4%, FEMALES: 89.6%
• CURRENT TREATMENT: Combination radiation and chemotherapy
• KEY DISEASE CHARACTERISTICS: Patients with breast, colorectal, lymphoma, and lung cancer
• OTHER KEY SAMPLE CHARACTERISTICS: The majority were chemotherapy naive.

• SITE: Multi-site   
• SETTING TYPE: Multiple settings    
• LOCATION: United States

• PHASE OF CARE: Active antitumor treatment

• Retrospective cohort comparison

FN episodes were identified based on hospital admission with a diagnosis of neutropenia, fever, or infection. FN episodes requiring outpatient care, including emergency department visits, were defined as Healthcare Common Procedure Coding System (HCPCS) code for IV antimicrobial therapy on the same date as a diagnosis of neutropenia, fever, or infection.

Of the patients, 5.3% were not given second-cycle pegfilgrastim prophylaxis. Second-cycle FN among comparison patients was 3.8% versus 2.2% among those who received propylaxis (95% confidence interval [CI] [1.2, 2.5], p = 0.002). With a narrower definition of FN, 3.5% without prophylaxis had FN compared to 0.8% in the group that received second-cycle pegfilgrastim (odds ratio [OR] = 3.5, p < 0.001).

The findings suggest that the odds of developing FN in the second cycle of chemotherapy are higher among patients who discontinue CSF prophylaxis compared to those who continue prophylaxis.

• Findings not generalizable
• Does not account for potential differences in absolute neutrophil count (ANC) between groups, which would account for different use of CSF prophylaxis
• No single diagnosis code exists for FN, so the definition is somewhat questionable, which could result in an under or overestimation of incidence.
• Included only patients younger than 65 years with private insurance, so it may not reflect other populations
• The study was funded by Amgen, Inc., which makes pegfilgrastim.

Some evidence suggest that ongoing CSF prophylaxis is not consistently provided in at-risk patients. This study, although it had some limitations, suggests that the discontinuation of prophylaxis along the course of treatment with myelosuppressive chemotherapy for patients at an intermediate or high risk for FN is associated with an increased incidence of FN.