Pancreatic cancer is a challenging disease with a low 5-year survival rate. There are areas for improvement in the tools used for screening, diagnosis, prognosis, treatment selection, and assessing treatment response. Liquid biopsy, particularly cell free DNA liquid biopsy, has shown promise as an adjunct to our standard care for pancreatic cancer patients, but has not yet been universally adopted into regular use by clinicians. In this publication, we aim to review cfDNA liquid biopsy in pancreatic cancer with an emphasis on current techniques, clinical utility, and areas of active investigation. We feel that researchers and clinicians alike should be familiar with this exciting modality as it gains increasing importance in the care of cancer patients.

Tumor heterogeneity, especially intratumoral heterogeneity, is a primary reason for treatment failure. A single biopsy may not reflect the complete genomic architecture of the tumor needed to make therapeutic decisions. Circulating tumor DNA (ctDNA) is believed to overcome these limitations. We analyzed concordance between ctDNA and whole-exome sequencing/whole-genome sequencing (WES/WGS) of tumor samples from patients with breast (n = 12), gastrointestinal (n = 20), lung (n = 19), and other tumor types (n = 13). Correlation in the driver, hotspot, and actionable alterations was studied. Three cases in which more-in-depth genomic analysis was required have been presented. A total 58% (37/64) of patients had at least one concordant mutation. Patients who had received systemic therapy before tissue next-generation sequencing (NGS) and ctDNA analysis showed high concordance (78% (21/27) vs. 43% (12/28) p = 0.01, respectively). Obtaining both NGS and ctDNA increased actionable alterations from 28% (18/64) to 52% (33/64) in our patients. Twenty-one patients had mutually exclusive actionable alterations seen only in either tissue NGS or ctDNA samples. Somatic hotspot mutation analysis showed significant discordance between tissue NGS and ctDNA analysis, denoting significant tumor heterogeneity in these malignancies. Increased tissue tumor mutation burden (TMB) positively correlated with the number of ctDNA mutations in patients who had received systemic therapy, but not in treatment-naïve patients. Prior systemic therapy and TMB may affect concordance and should be taken into consideration in future studies. Incorporating driver, actionable, and hotspot analysis may help to further refine the correlation between these two platforms. Tissue NGS and ctDNA are complimentary, and if done in conjunction, may increase the detection rate of actionable alterations and potentially therapeutic targets.

Room for improvement exists regarding recommendations for screening, staging, therapy selection, and frequency of surveillance of gastrointestinal cancers. Screening is costly and invasive, improved staging demands increased sensitivity and specificity to better guide therapy selection. Surveillance requires increased sensitivity for earlier detection and precise management of recurrences. Peripherally collected blood-based liquid biopsies enrich and analyze circulating tumor cells and/or somatic genomic material, including circulating tumor DNA along with various subclasses of RNA. Such assays have the potential to impact clinical practice at multiple stages of management in gastrointestinal cancers. This review summarizes current basic and clinical evidence for the utilization of liquid biopsy in cancers of the esophagus, pancreas, stomach, colon, and rectum. Technical aspects of various liquid biopsy methodologies and targets are reviewed and evidence supporting current commercially available assays is examined. Finally, current clinical applicability, potential future uses, and pitfalls of applying liquid biopsy to the screening, staging and therapeutic management of these diseases are discussed.

Tumor-associated glycosylation is a defining hallmark of cancer, exerting profound effects on multiple aspects of tumor biology. This phenomenon arises from the central role of glycosylation in a wide range of cellular processes and its inherently diverse structural complexity. In cancer cells, aberrant glycosylation often results in the modification of glycoconjugate structures, leading to alterations in cell surface architecture that disrupt cellular homeostasis and signaling pathways. These changes can enhance tumor cell proliferation, invasion, and metastasis by modulating cell adhesion, receptor activation, and intracellular communication. Beyond its direct impact on cancer cells, tumor-associated glycosylation plays a pivotal role in shaping the tumor microenvironment. Aberrant glycan structures influence immune cell infiltration by altering antigen presentation and immune checkpoint interactions, contributing to immune evasion. Additionally, these modifications regulate angiogenesis by affecting endothelial cell function and promoting the formation of aberrant vasculature, which supports tumor growth and metastasis. Glycosylation also mediates tumor–stroma interactions, influencing extracellular matrix remodeling and fibroblast activation, further enhancing cancer progression. This interplay between cancer-associated glycan modifications and their functional roles in tumorigenesis presents a promising therapeutic approach. Unlike conventional treatments, glycan-targeting therapies confer high tumor specificity, operate independently of canonical immune checkpoint targets, and help mitigate immune cell exhaustion. This review explores commonly dysregulated glycan motifs implicated in tumorigenesis and delves into their mechanistic contributions to cancer pathogenesis. We then highlight emerging opportunities for therapeutic intervention, including the development of glycan-targeted therapies and biomarker-driven strategies for cancer diagnosis and treatment. We also outline where glycan-targeted agents (e.g., desialylating biologics, glycomimetics, and anti-glycan mAbs) can complement checkpoint blockade and potentially overcome immune escape.

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