Table 2.

Liquid biopsy in the predicting prognosis of pancreatic cancer

Ref.	Journal	year	No. of patients	Biomarker	Method	Main findings
Singh et al[91], 2015	Cancer Invest	2015		cfDNA		Higher level of plasma DNA (> 62 ng/mL) was found to associate significantly with lower overall survival time (P = 0.002), presence of vascular encasement (P = 0.030) and metastasis (P = 0.001)
Lapin et al[92], 2018	J Transl Med	2018	61	cfDNA	2100 Bioanalyzer	Pre-treatment cfDNA levels could independently predict prognosis for both PFS (HR = 3.049, P = 0.005) and OS (HR = 2.236, P = 0.028)
Wang et al[93], 2021	Pancreas	2021	97	cfDNA	PCR	The 1- and 5-year survivals for those with high cfDNA were poorer; 70.2% and 21.2%, respectively, as compared with 93.4% and 23.7% for those with low cfDNA level
Castells et al[94], 1999	J Clin Oncol	1999	47	ctDNA	PCR-RFLP and SSCP	Plasma KRAS mutations were identified as the only independent prognostic factor (odds ratio, 1.51; 95%CI: 1.02 to 2.23)
Ako et al[95], 2017	Pancreatology	2017	40	ctDNA	ddPCR	KRAS mutation at G12V in the plasma or serum conferred a significantly poorer prognosis than without the mutation (P < 0.01)
Hadano et al[96], 2016	Br J Cancer	2016	105	ctDNA	ddPCR	Patients who were preoperative ctDNA+ had a significantly poorer prognosis with respect to OS (P < 0.0001)
Nakano et al[97], 2018	Br J Cancer	2018	45	ctDNA	PNA directed, PCR clamping	There were no significant differences in DFS and OS between patients with and without KRAS mutations from preoperative serum
Watanabe et al[98], 2019	PLoS One	2019	78	ctDNA	ddPCR	No effect of the presence of KRAS-mutated ctDNA before surgery on RFS (median: 16.9 mo vs 32.4 mo) was observed
Bernard et al[99], 2019	Gastroenterology	2019	34	ctDNA and exosome DNA	ddPCR	Increased exosome DNA levels after neoadjuvant therapy were significantly associated with disease progression (P = 0.003)
Kinugasa et al[100], 2015	Cancer	2015	75	ctDNA	ddPCR	KRAS mutations in plasma correlated with poor OS (P = 0.002)
Tjensvoll et al[101], 2016	Mol Oncol	2016	14	ctDNA	PNA clamp PCR	Kaplan-Meier survival analyses indicated that patients with a positive ctDNA before or after initiation of chemotherapy had shorter PFS and OS
Chen et al[102], 2010	Eur J Surg Oncol	2010	91	ctDNA	Direct sequencing	KRAS codon 12 mutation from plasma DNA was an independent negative prognostic factor (HR, 7.39; 95%CI: 3.69-14.89)
Sausen et al[103], 2015	Nat Commun	2015	101	ctDNA	Next-generation sequencing and digital PCR	ctDNA was an independent prognostic marker of OS in advanced disease, with OS of 6.5 mo vs 19.0 mo for ctDNA-positive and negative patients, respectively
Khoja et al[105], 2012	Br J Cancer	2012	54	CTC	Cellsearch and ISET	The PFS and OS for patients without vs those with CTCswas 140 d vs 94 d (P = 0.13) and 164 d vs 127 d (P = 0.26), respectively
Earl et al[106], 2015	BMC Cancer	2015	45	CTC	Cellsearch	A Cox regression analysis showed a significant difference in OS for CTC positive vs negative patients with a HR of 3.0 (P = 0.023)
Zhang et al[107], 2015	Int J Cancer	2015	61	CTC	The EpCAM-independent method	CTCs positive pancreatic cancer patients exhibit a worse (P = 0.0458) survival rate
Okubo et al[108], 2017	Eur J Surg Oncol	2017	65	CTC	Cellsearch	A multivariate analysis identified the presence or absence of CTCs as an independent prognostic factor (P = 0.049)
Ankeny et al[76], 2016	Br J Cancer	2016	100	CTC	Microfluidic NanoVelcro CTC chip	A cut-off of 3 CTCs in 4 mL venous blood was able to discriminate between local/regional and metastatic disease (AUROC = 0.885; 95%CI: 0.800-0.969; and P < 0.001)
Chang et al[109], 2016	Clin Chem	2016	63	CTM	anti-EpCAM conjugated supported lipid bilayer-coated microfluidic chips	CTM was an independent prognostic factor of OS and PFS (P 0.0001 and P = 0.003, respectively)
Bidard et al[110], 2013	Ann Oncol	2013	79	CTC	Cellsearch	CTC positivity was associated with poor tumor differentiation (P = 0.04), and with shorter OS in multivariable analysis (P = 0.01)
Kurihara et al[111], 2008	J Hepatobiliary Pancreat Surg	2008	47	CTC	Cellsearch	MST of the CTC-positive and -negative patients were 110.5 and 375.8 d (P < 0.001)
de Albuquerque et al[112], 2008	Oncology	2012	74	CTC		Median PFS time was 66.0 d for patients with baseline CTC positivity and 138.0 days for CTC-negative patients (P = 0.01)
Kulemann et al[81], 2015	Pancreas	2015	21	CTC	ScreenCell	The presence of CTC did not adversely affect MST: 16 mo in CTC-positive (n = 18) vs 10 mo in CTC-negative (n = 3) patients
Li et al[116], 2018	Cell Physiol Biochem	2018	73	miRNA	Arraystar Human miRCURYTM LNA Array	Multivariate analyses showed that exosomal miR-222 was independent risk factors for PDAC survival (P = 0.046)
Wang et al[117], 2018	Cancer Res	2018	50	miRNA	qRT-PCR	Exosomal miR-301a-3p overexpression predicted late TNM stage and poor survival in human PDAC (P = 0.0182)
Frampton et al[118], 2018	Oncotarget	2018	43	GPC1+ circulating exosomes	ELISA	Patients with high crExos GPC1 levels have significantly larger PDACs (> 4 cm; P = 0.012)
Costa-Silva et al[119], 2015	Nat Cell Biol	2015	55	Exosome	ELISA	Increased levels of MIF in exosomes isolated from patients with PDAC with progression of disease post-diagnosis compared with PDAC patients with no evidence of disease five years post-diagnosis (P < 0.01) and with healthy controls (P < 0.01), but not patients with liver metastasis

AUROC: Area under the curve; cfDNA: Cell-free DNA; ctDNA: Circulating tumor DNA; CTC: Circulating tumor cell; CTM: Circulating tumor microemboli; DFS: Disease-free survival; ddPCR: Droplet digital polymerase chain reaction; ELISA: Enzyme-linked immuno-sorbent assay; EPCAM: Epithelial cell adhesion molecule; ISET: Isolation by size of epithelial tumor cells; HR: Hazard ratio; MST: Median survival time; MIF: Macrophage migration inhibitory factor; miRNA: microRNA; OS: Overall survival; PFS: Progression-free survival; PCR: Polymerase chain reaction; PCR-RFLP: Polymerase chain reaction-restriction fragment length polymorphism; PNA: Peptide nucleic acid; PDAC: Pancreatic ductal adenocarcinoma; qRT-PCR: Quantitative reverse transcription polymerase chain reaction; RFS: Recurrence-free survival; SSCP: Single-strand conformation polymorphism.