Efforts to identify biomarkers for neuroblastoma (NB) have been ongoing, but no definite biomarker has been identified in peripheral blood. We proposed the use of plasma exosomal miRNAs as biomarkers of unfavorable NB patient outcomes. Exosomal miRNAs isolated from 31 plasma and 37 tissue samples, many from the same NB patients, were sequenced using a next-generation sequencing instrument. We analyzed the correlation between miRNA expression levels in plasma and tissue samples with International Neuroblastoma Risk Group staging system (INRGSS) outcome and MYCN status. We chose differentially expressed miRNAs with similar expression patterns in plasma and tissue samples in each of the three analysis groups and combined those miRNAs to find the optimal combination with the potential to be considered as a biomarker. MicroRNA-92a-3p was found to be significantly upregulated in deceased patients (p = 0.017), miR-375 was upregulated in INRGSS stage M patients (p = 0.002), and plasma miR-92a-3p and miR-99a-5 levels were upregulated in patients with MYCN amplification (p = 0.007 and 0.006). The combination of miR-92a-3p, miR-375, and miR-99a-5p levels was shown to be a statistically significant predictor of NB patient outcomes (AUC = 0.726, p = 0.001, 95% CI = 0.612–0.841, sensitivity = 77%, specificity = 56.7%). Thus, the combination of miR-92a3p, miR-375, and miR-99a-5p may potentially be used as a biomarker for unfavorable NB patient outcomes. However, further validation is required in a larger number of NB patients.This research was partially supported by a Grant-in-Aid for Scientific Research (A) (No.19H0105600) from the Ministry of Education, Culture, Sports, Science and Technology
