Liquid Biopsy in Low-Grade Glioma: A Systematic Review and a Proposal for a Clinical Utility Score

Liquid biopsy research on Low-Grade gliomas (LGG) has remained less conspicuous than that on other malignant brain tumors. Reliable serum markers would be precious for diagnosis, follow- up and treatment. We propose a clinical utility score (CUS) for biomarkers in LGG that mirrors their clinical usefulness. We conducted a PRISMA review. We examined each biomarker classifying them by CUS and Level of Evidence (LOE). We identified four classes of biomarkers: (1). Circulating protein—(a) vitronectin discriminates LGG from HGG (Sn:98%, Sp:91%, CUS: 3, LOE: III), (b) CTLA-4 discriminates LGG from HGG, (cutoff: 220.43 pg/ml, Sn: 82%, Sp: 78%, CUS:3, LOE:III), (c) pre-operative TGF b1 predict astrocytoma (cutoff: 2.52 ng/ml, Sn: 94.9%, Sp: 100%, CUS:3, LOE:VI). (2). micro-RNA (miR)—(a) miR-16 discriminates between WHO IV and WHO II and III groups (AUC = 0.98, CUS:3, LOE: III), (b) miR-454-3p is higher in HGG than in LGG (p = 0.013, CUS:3, LOE: III), (c) miR-210 expression is related to WHO grades (Sn 83.2%, Sp 94.3%, CUS: 3, LOE: III). (3). Circulating DNA—(a) IDH1R132H mutation detected in plasma by combined COLD and digital PCR (Sn: 60%, Sp: 100%, CUS: 3, LOE: III). 4. Exosomes—(a) SDC1 serum levels could discriminate GBM from LGG (Sn: 71%, Sp: 91%, CUS: 2C, LOE: VI). Our investigation showed that miRs appear to have the highest clinical utility. The LOE of the studies assessed is generally low. A combined approach between different biomarkers and traditional diagnostics may be considered. Graphical Abstract We identified four main classes of biomarkers produced by LGG. We examined each biomarker, classifying them by clinical utility score (CUS) and level of evidence (LOE). Micro-RNA (miRs) appears to have the highest CUS and LOE.