Table 6.

Applications of liquid biopsy in Agnostic therapy

Target	Methods	Findings	Challenges	References
bTMB	Foundation Medicine bTMB assay	High bTMB was associated with greater ORR and a trend toward increasing OS and PFS benefit in patients with NSCLC treated with first-line atezolizumab	-lack of standardisation in the technique for detecting bTMB -lack of standardization in defining cut-off points for high bTMB - lack of evidence in several type of cancers	[155, 156]
MSI/dMMR	Guardant360® CDx and the liquid CDx FoundationOne	A high degree of concordance between tissue-based MSI determination and MSI determination based on circulating tumour DNA has been reported in the literature	- Detection limits due to low disease burden, location of metastasis or concurrent treatment (chemotherapy/radiotherapy) - most evidence of accuracy found in colorectal cancer	[157, 158]
NTRK re-arrangements	Plasma based NGS-assay	-In a retrospective study the NTRK1 fusion detected by ctDNA was confirmed in tissue in 88% of cases - plasma-based NGS tests demonstrated high concordance with tissue genotyping in several reports including NTRK genes fusion in the panel	Lack of previous reports in literature evaluating the role of cfDNA analysis in NTRK fusion positive solid tumours	[159, 160]
BRAF mutation V600E	- NGS platform - Idylla platform, real-time PCR based test	- High sensitivity and specifity - concordance between plasma and tissue analysis	Most of the literature concerns colon- rectal cancers, NSCLC and melanoma	[161–166]

bTMB blood Tumor mutational burden, ORR Overall response rate, PFS Progression free survival, OS Overall survival, dMMR deficiency of DNA mismatch repair, MSI Microsatellite instability, NGS Next generation sequencing, NTRK Neurotrophic receptor tyrosine kinase, NSCLC No small cell lung cancer