Liquid biopsies in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer-related mortality. Most patients with early-stage PDAC are asymptomatic and the disease is usually diagnosed at advanced stages. Patients diagnosed with PDAC have a 5-year survival rate of less than 8%. Currently, traditional tumor biopsy is the main approach for pancreatic cancer diagnosis; however, it often provides limited information on tumor specimens due to their complex cellular composition and spatial heterogeneity between the primary tumor and distant metastasis. In addition, repeated tissue biopsy is not feasible. Liquid biopsy is a minimally invasive method for the real-time monitoring of cancer biomarkers such as circulating tumor cells (CTCs), circulating tumor DNAs (ctDNAs), and extracellular vesicles (EVs) for diagnosis and disease monitoring. Longitudinal sampling of cancer biomarkers provides an effective prognostic tool to evaluate treatment response. In this chapter, we describe the biology of blood-derived actionable biomarkers, outline methods for their enrichment/isolation, report their clinical applications, show correlative studies for PDAC diagnosis and prognosis, and describe recent advances of liquid biopsy approaches in pancreatic cancer research.