Prospective Analyses of the Utility of Liquid Biopsy in Patients with Fever of Unknown Origin Suspected of Lymphoma

Diagnosing malignant lymphomas, including intravascular large B-cell lymphoma (IVLBCL), is sometimes challenging due to the absence of detectable mass lesions. Random skin biopsy (RSB) can enhance diagnostic sensitivity, but its utility remains limited. Liquid biopsy mainly analyzes peripheral blood cell-free DNA (cfDNA), offering promise as a less-invasive alternative. This study aimed to assess the diagnostic value of genetic analyses using cfDNA in patients showing fever of unknown origin (FUO) with suspected lymphoma at onset. We enrolled FUO patients suspicious of lymphoma and analyzed blood samples for plasma cfDNA concentration, MYD88 L265P and CD79B Y196 mutations using droplet digital polymerase chain reaction, B-cell receptor (BCR) and T-cell receptor rearrangements, and genetic profiles via next-generation sequencing (NGS). Results were compared with conventional diagnostic strategies of bone marrow aspiration and/or biopsy (BMAB) and RSB. Of the 49 patients, 28 (57%) were finally diagnosed with lymphoma, including 17 (35%) with IVLBCL. Analysis using cfDNA outperformed conventional methods for IVLBCL, detecting BCR clonality in 88.2% of cases and MYD88/CD79B mutations in 94.1%, compared to detection rates of 53% for both RSB and BMAB. NGS identified recurrent mutations, such as MYD88/CD79B , and immune escape-related alterations including CD274 and PDCD1LG2 . Mutation patterns from cfDNA were closely concordant with those in tumor tissue for non-IVLBCL, whereas in IVLBCL, cfDNA detected mutations with higher sensitivity than those in tissue samples. These results suggest that genetic analysis using cfDNA may enable prompt detection of malignant lymphomas, particularly for IVLBCL, which presents with FUO and is difficult to detect using conventional diagnostic strategies. UMIN000040061 (250 words)