表 3.

免疫检查点抑制剂治疗相关外周血标志物的优缺点

Advantages and limitations of the main blood biomarkers under investigation in the area of immune checkpoint inhibitors-based therapy

Item	Composition	Advantages	Disadvantages	Level of evidence
WES: whole exon sequencing; CTCs: circulating tumor cells.
ctDNA levels	Nucleic acid	Highly specific and sensitive, real time quantitative analysis enable dynamic evaluation of tumor at a precise moment, covering spatial and temporal tumor heterogeneity	Lack of standardization of pre-analytical and detection methods, time-consuming	Prospective study
bTMB	Nucleic acid	Standardized detection technology: WES is the gold standard while NGS can serve as a sufficiently fast candidate tests, covering spatial and temporal tumor heterogeneity	Lack of standardization of pre-analytical methods. WES: long and very expensive, NGS: optimal gene panel size, algorithm and a consensual cut-off defining high TMB are still to be determined, expensive	Prospective study
CTC	Living cells	Specific, single-cell analysis. CellSearch: standardized, semiautomated, covering spatial and temporal tumor heterogeneity	Very rare, hard to keep, variability of technologies, expensive	Retrospective study
Exosomes	Nucleic acid, protein	Widely distributed and good stability, unique surface protein and genetic material originated from their parental cells, covering spatial and temporal tumor heterogeneity	Technology for exosomal isolation and tests is not broadly available	Retrospective study
Circulating immune cells	Immune cell subpopulations	Reflecting the host's immune status, Simultaneous detection of multiple subpopulations	Lack of standardized methodological approaches, complex classification, highly dynamic and the optimal target and detecting timing are still to be determined, long technical and analysis time	Retrospective study