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Real-World Impact of Baseline Risk Factors on Incidence of Febrile Neutropenia in Patients With Breast Cancer
Findings from a real-world study show the choice of febrile neutropenia (FN) definition significantly changed the impact of risk factors on febrile neutropenia outcomes among patients with breast cancer receiving chemotherapy with pegfilgrastim prophylaxis (JHEOR. 2021;8[1]:106-115. doi:10.36469/001c.24564).
“There are sparse data addressing whether standard risk factors for FN are relevant in patients receiving myelosuppressive chemotherapy and primary prophylaxis for FN, which would have implications for variables to consider during real-world comparative analyses of FN incidence,” wrote Edward Li, PharmD, Sandoz, Inc, Princeton, NJ, and colleagues.
This retrospective observational study used MarketScan research databases to identify 4460 patients with breast cancer who received myelosuppressive chemotherapy and prophylactic pegfilgrastim between January 1, 2017, and May 31, 2018.
Three definitions for FN were used to define incidence of FN among various cycles of chemotherapy. Dr Li and colleagues compared outcomes among patients with and without patient-specific risk factors and among those receiving regimens categorized as high-, intermediate-, or other-risk for FN, using logistic regression and generalized estimating equation models.
Results suggested that patients receiving intermediate-risk regimens in the first cycle of therapy were at up to 2 times higher risk for FN across all definitions in the first cycle of therapy compared to those receiving high-risk regimens. The odds ratio for main FN was 15.8 among patients with 4 or more vs 0 risk factors, while patients with 3 or more FN risk factors had significantly higher risks for all definitions of FN across all cycles of treatment compared to those with no risk factors.
Variations in the definition of FN played a significant role in changing the impact of risk factors on the FN outcomes, demonstrating that evaluating all proxies for true FN events is crucial in real-world database studies, otherwise, biases or confounding effects could occur in the results.
“In patients with breast cancer receiving chemotherapy with pegfilgrastim prophylaxis, patient-specific risk factors and regimen risk levels are determinants of FN risk,” concluded Dr Li and colleagues.
“In real-world studies evaluating FN incidence, it is imperative to consider and control for these risk factors when conducting comparative analyses,” they added.—Marta Rybczynski
