Fever in Children with Cancer: Pathophysiological Insights Using Blood Transcriptomics

Abstract

Fever is a frequent complication in children receiving chemotherapy, primarily caused by bloodstream infections and non-infectious inflammation. Yet, the pathophysiological mechanisms remain unclear, and diagnostics are insufficient, which often results in continued antibiotic treatment despite negative blood cultures. In a nationwide study, we collected whole blood in PAXgene tubes from 168 febrile episodes in children with hematological malignancies, including 37 episodes with bacteremia, and performed single-cell RNA sequencing. We compared transcriptomic profiles between febrile children with and without bacteremia. In children with bacteremia, differentially expressed genes were related to immunoregulation and cardiac and vascular function. Children without bacteremia had distinct gene expression patterns, suggesting a viral or other inflammatory cause of fever. Several differentially expressed genes overlapped with previously published transcriptomics-based diagnostic signatures developed in immunocompetent children. In conclusion, blood transcriptomics provided novel insights into the pathophysiological mechanisms of febrile children with hematological malignancies. We found differentially expressed genes suggesting viral infections or non-bacterial inflammation as causes of fever in children with negative blood cultures, supporting early antibiotic discontinuation in children with cancer.

Keywords: bloodstream infection; differential gene expression; febrile neutropenia; pediatric oncology; transcriptomics.

Figure 1

Classification of febrile episodes. Febrile children were classified according to blood cultures and CRP. The primary comparison was between febrile episodes with bacteremia and unexplained fever with low CRP. Seventeen (9%) samples from 185 febrile episodes were excluded (6 during processing steps and 11 after quality control), resulting in a final study population of 168 episodes. CoNS = Coagulase-negative staphylococci; CRP = C-reactive protein.

Figure 2

Volcano plot illustrating differentially expressed genes between febrile episodes with bacteremia and unexplained fever with low CRP on day 1 (A) and day 2 (B). Each point represents a gene. The x-axis represents the log₂ fold change, and the y-axis represents the log₁₀ (p-value). The dashed lines represent the statistical significance thresholds after adjusting for multiple testing. Upregulated genes in children with bacteremia compared to unexplained fever with low CRP-reactive protein are shown in red, such as C-X-C Motif Chemokine Ligand 1 (CXCL1), and downregulated in blue, such as ISG15 Ubiquitin Like Modifier (ISG15). Genes that did not differ significantly between groups are gray. One gene overlapped between the day 1 and day 2 samples.

Figure 3

Gene enrichment pathways. Biological process enrichment analysis of differentially expressed genes across four comparisons: (A) Bacteremia day 1 versus unexplained fever with low CRP, (B) bacteremia day 2 versus unexplained fever with low CRP day 2, (C) unexplained fever with high CRP day 1 versus bacteremia day 1, and (D) coagulase-negative staphylococci day 1 versus bacteremia day 1. Pathways were identified through Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and displayed by Normalized Enrichment Score (NES), which reflects the direction and strength of enrichment. NES > 0 indicates upregulated pathways and NES < 0 indicates downregulated pathways in the first group of each comparison. NES are shown on the x-axis, and gene set names are on the y-axis. NES = Normalized Enrichment Score.

Figure 3

Gene enrichment pathways. Biological process enrichment analysis of differentially expressed genes across four comparisons: (A) Bacteremia day 1 versus unexplained fever with low CRP, (B) bacteremia day 2 versus unexplained fever with low CRP day 2, (C) unexplained fever with high CRP day 1 versus bacteremia day 1, and (D) coagulase-negative staphylococci day 1 versus bacteremia day 1. Pathways were identified through Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and displayed by Normalized Enrichment Score (NES), which reflects the direction and strength of enrichment. NES > 0 indicates upregulated pathways and NES < 0 indicates downregulated pathways in the first group of each comparison. NES are shown on the x-axis, and gene set names are on the y-axis. NES = Normalized Enrichment Score.

Figure 4

The performance of the previously published 2-gene signature, including ADGRE1 and IFI44L, for unexplained fever with low and high CRP protein, coagulase-negative staphylococci, and bacteremia. To investigate the performance of the 2-gene signature, a disease risk score for each febrile episode was calculated by subtracting log2 IFI44L expression from log2 ADGRE1 expression. The dotted line represents the proposed threshold of 0 or above for assignment to bacterial infections [25,26]. All calculations used febrile episodes on day 1.