Detecting circulating tumor material and digital pathology imaging during pancreatic cancer progression

Table 1 Summary of demonstrated clinical uses for digital pathology, circulating tumor cells and extracellular vesicles for pancreatic cancer

	Digital pathology	CTCs	EVs
Screening in population	Relies on invasive biopsies	Detection of KRAS mutations[92]	Early detection possibility (GPC1+ EVs)[117]
			GPC1+ EVs detected in IPMNs[117]
Diagnosis	Differential diagnosis of mucinous cancers[62]	Pancreatic CTC detected by ISET[82] and CellSearch[81]	EVs express mutated KRAS and p53 in PDAC serum[123] EVs detected in pancreaticobiliary cancers[124]
Staging	Early stage detection in mice[60] Distinguish Grade I/II in humans[61]	(C-MET, CK20, CEA) + CTCs elevated in late stages[96]	miR-17-5p in serum exosomes correlates with stage[128]
Prognosis	Potential	CTC positivity has prognostic value in locally advanced pancreatic cancer[81] CK20 expression in CTC indicates shorter overall survival[94]	Potential
Monitor treatment	Potential	CTC levels decrease during 5-FU therapy[91]	Potential
Drug sensitivity/ pharmacokinetics	CT scans can predict drug transport[35]	CTC apoptosis can be detected after 5-FU therapy[91]	Demonstrated for breast cancer[111]
Monitor recurrence	Potential	CTC positivity correlates with postoperative staging[94-97]	potential

EVs: Extracellular vesicles; CTCs: Circulating tumor cells; 5-FU: 5-Fluorouracil; PDAC: Pancreatic ductal adenocarcinoma; CT: Computed tomography; PDAC: Pancreatic ductal adenocarcinoma; CEA: Carcino-embryonic antigen.

Table 2 Clinical uses for biomarker panels that increase predictive value of CA 19-9 for pancreatic cancer

	CA 19-9	Sensitivity	Specificity	Ref.
Screening in	EUS-FNA	75%-94%	78%-95%	[42]
population	CA 19-91	60%-70%	70%-85%	[45,46]
Differential	CA 19-9	60%	83%	[44]
diagnosis	CA 19-9 + CA 125	87%	77%	[44]
	CA 19-9 + ICAM-1 + OPG	78%	94%	[49]
	CA 19-9 + CEA + TIMP-1	71%	89%	[49]
Staging	PAM4-reactive mucins	76%	85%	[51]
	CA 19-9 + PAM4-reactive mucins	84%	82%	[51]
Monitor treatment	Response to chemotherapy			[47]
Monitor recurrence	Low levels post-surgery correlate with survival			[45]

¹Values reflect subjects presented with pancreatobilliary disease. EUS-FNA: Endoscopic ultrasound and fine needle aspiration; OPG: Osteoprotegerin; ICAM-1: Intercellular adhesion molecule 1; CEA: Carcinoembryonic antigen; TIMP-1: Tissue inhibitor of metalloproteinases 1; clivatuzumab monoclonal antibody (PAM4) to MUC5AC.

Table 3 Challenges and potential solutions for pancreatic cancer diagnosis and treatment

Challenges	Potential solutions
Metastatic probability increases dramatically with larger tumor size	Promote development of early detection methods (circulating tumor cells, extracellular vesicles, molecular cargo in CTCs and EVs, cfDNA, ctDNA)
Tumor mutations develop up to two decades with metastatic mutations occurring late in the process	Identify founder mutations that correlate with unusual survival outcomes
Pancreatic stroma influences treatment sensitivity	Promote research on stromal characterization
Transporter expression in the tumor impacts drug delivery	Identify expression features that correlate with treatment sensitivity to a variety of drugs
CA 19-9 is not pancreatic cancer specific	Promote development of assays for biomarker panels that increase CA 19-9 utility that will be eligible for FDA approval
Prediction of resectability is only 70%-85% accurate	Improve staging based on biopsies by implementing clinical use of digital pathology methods
No FDA-approved digital pathology methods exist for pancreatic cancer	Combine digital pathology with accepted primary diagnostic methods and test special controls for digital imaging that will permit FDA application through a more streamlined de novo pathway

CTC: Circulating tumor cells; EVs: Extracellular vesicles; cfDNA: Circulating free DNA; ctDNA: Circulating tumor DNA; FDA: Food and Drug Administration.