Circulating Tumor DNA Detection by Digital-Droplet PCR in Pancreatic Ductal Adenocarcinoma: A Systematic Review

Comprehensive Genome Profiling-Initiated Tumor-Informed Circulating Tumor DNA Monitoring for Patients With Advanced Cancer

In Japan, comprehensive genome profiling (CGP) as a companion diagnostic (CDx) has been covered by public insurance since June 2019, but the proportion of patients with cancer who actually received drug therapy based on CGP data is low. In the present study, we attempted to use CGP as a starting point for tumor-informed circulating tumor DNA (ctDNA) monitoring. We retrospectively validated 219 patients with malignant tumors who underwent CGP at Iwate Medical University Hospital between October 2019 and April 2023 in terms of patient demographics, genetic analysis, drug recommendations, and drug administration rate. The 219 cancer cases analyzed by CGP for 27 target organs, including prostate (n = 27, 12.3%), colorectal (n = 25, 11.4%), lung (n = 19, 8.7%), and other neoplasms (n = 148, 67.6%). Among the cohort, only 14 cases (6.4%) subsequently were able to undertake the recommended action by Molecular Tumor Board. Of patients who underwent ctDNA monitoring based on somatic mutations identified by CGP (n = 11), clinical validity was confirmed in terms of early relapse prediction (n = 5, 45.5%), treatment response evaluation (n = 10, 90.9%), and no relapse/regrowth corroboration (n = 2, 18.2%) whereas 90.9% (n = 10) of patients obtained information with at least one source of the clinical validity. Although the current rate of CGP contributing to a drug recommendation is low, CGP results can be an alternate resource for tumor-informed longitudinal ctDNA monitoring to provide information concerning early relapse prediction, treatment response evaluation, and no relapse/regrowth corroboration.

Circulating tumor DNA detection improves relapse prediction in epithelial ovarian cancer

BACKGROUND

Epithelial ovarian cancer (EOC) is a lethal form of gynecological malignancy. Some EOC patients experience relapse after standard primary debulking surgery (PDS) and adjuvant chemotherapy (ACT). Identifying molecular residual disease (MRD) by circulating tumor DNA (ctDNA) detection can timely signal the potential for relapse. However, research on the usage of ctDNA for MRD detection in EOC is limited.

METHODS

Fifty-one EOC patients who received standard PDS and ACT were included. Targeted sequencing based on a panel of 1021 cancer-related genes, along with further validation using Enrich-rare-mutation sequencing, was performed on tumor tissues acquired during PDS and on plasma samples collected before and after PDS/ACT to identify variants reflecting tumor signals.

RESULTS

Post-surgery MRD was associated with relapse (Log-rank p = 0.0006) and was identified as an independent prognostic factor (HR, 3.4; 95% CI, 1.02-11.42; p = 0.047). The negative and positive predictive values were 0.83 and 0.62 respectively. Additionally, post-surgery MRD outperformed CA125 in predicting relapse, and integrating both parameters could provide more accurate risk stratification. Post-ACT MRD detection identified the patients with ctDNA clearance who were still at risk of relapse. Furthermore, baseline ctDNA detection could help determine patients who are not suitable for further tests after surgery.

CONCLUSIONS

Post-surgery MRD is superior to CA125 in predicting relapse in EOC. Patients exhibiting transient ctDNA clearance, as evaluated by post-ACT MRD, may require longitudinal monitoring. Baseline ctDNA detection could help determine whether post-surgery ctDNA monitoring should be performed.

The role of circulating tumor DNA in melanomas of the uveal tract

Melanoma of the uveal tract or uveal melanoma (UM) originates from melanocytes of the eye and is the most common intraocular malignancy in adults. Despite considerable advances in diagnostic procedures and treatments, prognosis remains poor in those with advanced disease. Accordingly, although current treatments have an excellent local disease control rate, approximately 50% of patients develop metastatic relapse within 10 years. The high risk for metastatic disease with a variable and often long latency period is thought to be due to early spread of cancer cells disseminating into organs such as the liver, followed by a period of dormancy, before the eventual emergence of radiologically measurable disease. Early detection of disease relapse or metastasis is therefore crucial to allow timely treatment and ultimately improve patient outcome. Recently, advances in minimally-invasive liquid biopsy techniques and biomarkers such as circulating tumor DNA (ctDNA) have demonstrated potential to transform the field of cancer care by aiding diagnosis, prognosis and monitoring of various cancer types. UM is particularly suitable for ctDNA-based approaches due to the relatively well-characterized spectrum of genetic mutations, along with the inherent difficulties and risks associated with getting sufficient tumor samples via traditional biopsy methods. Key potential advantage of ctDNA are the detection of molecular residual disease (MRD) in patients post definitive treatment, and in the early identification of metastasis. This is particularly relevant contemporarily with the recent demonstration of tebentafusp improving survival in metastatic UM patients, and opens avenues for further research to investigate the potential utilization of tebentafusp combined with ctDNA-based strategies in adjuvant settings and early intervention for MRD. The present review illustrates the current understanding of ctDNA-based strategies in UM, discusses the potential clinical applications, explores the potential of utilizing ctDNA in UM MRD in the context of an ongoing clinical trial, and highlights the challenges that need to be overcome prior to routine clinical implementation.

Prognostic impact of circulating tumor DNA detection in portal and peripheral blood in resected pancreatic ductal adenocarcinoma patients

In PDAC patients, ctDNA detection's prognostic significance needs validation especially in resected patients. This study investigated ctDNA kinetics in portal and peripheral blood before and after resection, and whether tissue mobilization during surgery influences ctDNA detection. In this single-center prospective cohort, portal and peripheral blood were drawn during pancreaticoduodenectomy before and after tissue mobilization, during 12 postoperative months and were associated with overall survival (OS), recurrence-free survival (RFS) and CA19-9 (secondary endpoints). Tumor mutations were identified using next-generation-sequencing and ctDNA detected by digital droplet PCR. From 2018 to 2022, 34 patients were included. The 2-year RFS and OS were 47.6%(95%CI[29.5; 63.6]) and 65.7%(95%CI[46.5; 79.4]) respectively. Intraoperatively, ctDNA detection in portal or peripheral blood was associated with worse RFS (HR[95%CI]3.26[1.26; 8.45],p = 0.010) and OS (HR[95%CI]5.46[1.65;18.01],p = 0.002). Portal vein sampling did not improve ctDNA detection. CtDNA levels were increased by 2.5-fold (p = 0.031) in peripheral blood after tissue mobilization but not significantly linked to RFS or OS. Detecting ctDNA intraoperatively was correlated with poorer RFS (HR [95% CI] 3.26 [1.26;8.45], p = 0.010) and 0S (HR [95% CI] 5.46 [1.65;18.01], p = 0.002). Portal vein sampling did not improve ctDNA detection. Tissue mobilization increases ctDNA levels. Intraoperative detection of ctDNA is associated with a worse prognosis.

Circulating tumor DNA methylation detection as biomarker and its application in tumor liquid biopsy: advances and challenges

Circulating tumor DNA (ctDNA) methylation, an innovative liquid biopsy biomarker, has emerged as a promising tool in early cancer diagnosis, monitoring, and prognosis prediction. As a noninvasive approach, liquid biopsy overcomes the limitations of traditional tissue biopsy. Among various biomarkers, ctDNA methylation has garnered significant attention due to its high specificity and early detection capability across diverse cancer types. Despite its immense potential, the clinical application of ctDNA methylation faces substantial challenges pertaining to sensitivity, specificity, and standardization. In this review, we begin by introducing the basic biology and common detection techniques of ctDNA methylation. We then explore recent advancements and the challenges faced in the clinical application of ctDNA methylation in liquid biopsies. This includes progress in early screening and diagnosis, identification of clinical molecular subtypes, monitoring of recurrence and minimal residual disease (MRD), prediction of treatment response and prognosis, assessment of tumor burden, and determination of tissue origin. Finally, we discuss the future perspectives and challenges of ctDNA methylation detection in clinical applications. This comprehensive overview underscores the vital role of ctDNA methylation in enhancing cancer diagnostic accuracy, personalizing treatments, and effectively monitoring disease progression, providing valuable insights for future research and clinical practice.

MSI-H Detection by ddPCR in Endoscopic Ultrasound Fine Needle Biopsy (EUS-FNB) from Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease with limited survival. Curative opportunities are only available for patients with resectable cancer. Palliative chemotherapy is the current standard of care for unresectable tumors. Numerous efforts have been made to investigate new therapeutic strategies for PDAC. Immunotherapy has been found to be effective in treating tumors with high microsatellite instability (MSI-H), including PDAC. The ability of the Endoscopic Ultrasound Fine Needle Biopsy (EUS-FNB) to reliably collect tissue could enhance new personalized treatment by permitting genomic alterations analysis. The aim of this study was to investigate the feasibility of obtaining adequate DNA for molecular analysis from EUS-FNB formalin-fixed-paraffin-embedded (FFPE) specimens. For this purpose, FFPE-DNA obtained from 43 PDAC archival samples was evaluated to verify adequacy in terms of quantity and quality and was tested to evaluate MSI-H status by droplet digital PCR (ddPCR). All samples were suitable for ddPCR analysis. Unlike the 1-2% MSI-H frequency found with traditional techniques, ddPCR detected this phenotype in 16.28% of cases. This study suggests the ddPCR ability to identify MSI-H phenotype, with the possibility of improving the selection of patients who may benefit from immunotherapy and who would be excluded by performing traditional diagnostic methods.

Diagnostic use of circulating cells and sub-cellular bio-particles

In the bloodstream or other physiological fluids, "circulating cells and sub-cellular bio-particles" include many microscopic biological elements such as circulating tumor cells (CTCs), cell-free DNA (cfDNA), exosomes, microRNAs, platelets, immune cells, and proteins are the most well-known and investigated. These structures are crucial biomarkers in healthcare and medical research for the early detection of cancer and other disorders, enabling treatment to commence before the onset of clinical symptoms and enhancing the efficacy of treatments. As the size of these biomarkers to be detected decreases and their numbers in body fluids diminishes, the detection materials, ranging from visual inspection to advanced microscopy techniques, begin to become smaller, more sensitive, faster, and more effective, thanks to developing nanotechnology. This review first defines the circulating cells and subcellular bio-particles with their biological, physical, and mechanical properties and second focuses on their diagnostic importance, including their most recent applications as biomarkers, the biosensors that are utilized to detect them, the present obstacles that must be surmounted, and prospective developments in the domain. As technology advances and biomolecular pathways are deepens, diagnostic tests will become more sensitive, specific, and thorough. Finally, integrating recent advances in the diagnostic use of circulating cells and bioparticles into clinical practice is promising for precision medicine and patient outcomes.

Evolution of Liquid Biopsies for Detecting Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy characterised by late diagnosis and poor prognosis. Despite advancements, current diagnostic and prognostic strategies remain limited. Liquid biopsy techniques, including circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), circulating tumour exosomes, and proteomics, offer potential solutions to improve PDAC diagnosis, prognostication, and management. A systematic search of Ovid MEDLINE identified studies published between 2019 and 2024, focusing on liquid biopsy biomarkers for PDAC. A total of 49 articles were included. ctDNA research shows some promise in diagnosing and prognosticating PDAC, especially through detecting mutant KRAS in minimal residual disease assays. CTC analyses had low sensitivity for early-stage PDAC and inconsistent prognostic results across subpopulations. Exosomal studies revealed diverse biomarkers with some diagnostic and prognostic potential. Proteomics, although relatively novel, has demonstrated superior accuracy in PDAC diagnosis, including early detection, and notable prognostic capacity. Proteomics combined with CA19-9 analysis has shown the most promising results to date. An update on multi-cancer early detection testing, given its significance for population screening, is also briefly discussed. Liquid biopsy techniques offer promising avenues for improving PDAC diagnosis, prognostication, and management. In particular, proteomics shows considerable potential, yet further research is needed to validate existing findings and comprehensively explore the proteome using an unbiased approach.

From haystack to high precision: advanced sequencing methods to unraveling circulating tumor DNA mutations

Identifying mutations in cancer-associated genes to guide patient treatments is essential for precision medicine. Circulating tumor DNA (ctDNA) offers valuable insights for early cancer detection, treatment assessment, and surveillance. However, a key issue in ctDNA analysis from the bloodstream is the choice of a technique with adequate sensitivity to identify low frequent molecular changes. Next-generation sequencing (NGS) technology, evolving from parallel to long-read capabilities, enhances ctDNA mutation analysis. In the present review, we describe different NGS approaches for identifying ctDNA mutation, discussing challenges to standardized methodologies, cost, specificity, clinical context, and bioinformatics expertise for optimal NGS application.

Decoding the Dynamics of Circulating Tumor DNA in Liquid Biopsies

Circulating tumor DNA (ctDNA), a fragment of tumor DNA found in the bloodstream, has emerged as a revolutionary tool in cancer management. This review delves into the biology of ctDNA, examining release mechanisms, including necrosis, apoptosis, and active secretion, all of which offer information about the state and nature of the tumor. Comprehensive DNA profiling has been enabled by methods such as whole genome sequencing and methylation analysis. The low abundance of the ctDNA fraction makes alternative techniques, such as digital PCR and targeted next-generation exome sequencing, more valuable and accurate for mutation profiling and detection. There are numerous clinical applications for ctDNA analysis, including non-invasive liquid biopsies for minimal residual disease monitoring to detect cancer recurrence, personalized medicine by mutation profiling for targeted therapy identification, early cancer detection, and real-time evaluation of therapeutic response. Integrating ctDNA analysis into routine clinical practice creates promising avenues for successful and personalized cancer care, from diagnosis to treatment and follow-up.

Functionalized primer initiated signal cycles and personal glucose meter for sensitive and portable miRNA analysis

MicroRNA (miRNA) has garnered considerable attention due to its diagnostic capabilities, such as in hypoxic cognitive impairment and cancers. However, the existing miRNA detection methods are commonly criticized for the drawbacks of low sensitivity and false-positive detection derived from interfering molecules. Here, we provide a novel, sensitive and portable method for miRNA detection by combining target identification based cyclization of padlocks, immobilized primer-based signal amplification and a personal glucose meter. The proposed method exhibits several advantages, including precise identification of specific sites, exceptional sensitivity and instrument-free feature. These attributes hold great promise for the diagnosis and clinical investigation of various diseases, such as cancer and hypoxic cognitive impairment, enabling a deeper understanding of their pathological and physiological aspects.

The Development of a Sensitive Droplet Digital Polymerase Chain Reaction Test for Quantitative Detection of Goose Astrovirus

(1) Goose astrovirus (GAstV) is a novel emerging pathogen that causes significant economic losses in waterfowl farming. A convenient, sensitive, and specific detection method for GAstV in field samples is important in order to effectively control GAstV. Droplet digital polymerase chain reaction (ddPCR) is a novel, sensitive, good-precision, and absolute quantitation PCR technology which does not require calibration curves. (2) In this study, we developed a ddPCR system for the sensitive and accurate quantification of GAstV using the conserved region of the ORF2 gene. (3) The detection limit of ddPCR was 10 copies/µL, ~28 times greater sensitivity than quantitative real-time PCR (qPCR). The specificity of the test was determined by the failure of amplification of other avian viruses. Both ddPCR and qPCR tests showed good repeatability and linearity, and the established ddPCR method had high sensitivity and good specificity to GAstV. Clinical sample test results showed that the positive rate of ddPCR (88.89%) was higher than that of qPCR (58.33%). (4) As a result, our results suggest that the newly developed ddPCR method might offer improved analytical sensitivity and specificity in its GAstV measurements. The ddPCR could be widely applied in clinical tests for GAstV infections.

Next‑generation sequencing to identify genetic mutations in pancreatic cancer using intraoperative peritoneal washing fluid

The efficacy of next-generation sequencing (NGS) of tumor-derived DNA from intraoperative peritoneal washing fluid (IPWF) of patients with pancreatic ductal adenocarcinoma (PDAC) who intend to undergo curative resection remains unclear. The aim of the present study was to evaluate whether genomic mutations in tumor-derived DNA from IPWF samples of patients with PDAC who intend to undergo curative resection could be detected using NGS. A total of 12 such patients were included in this study. Cytology of IPWF (CY) was assessed and NGS of genomic tumor-derived DNA from the IPWF was performed to determine whether genomic mutations could be detected in these patient samples. A total of 2 patients (16.7%) had a CY(+) status and 1 patient (8.3%) showed intraoperative macro-peritoneal dissemination; 11 patients underwent radical surgery. Actionable gene alterations were detected in 8 (80.0%) out of the 10 patients with CY(-) status based on NGS of IPWF samples, and 3 (37.5%) patients among those with actionable gene mutations identified from IPWF samples underwent peritoneal dissemination after surgery within ~12 months. The most common genomic mutation was in KRAS (9 patients, 75.0%), followed by TP53 (3 patients, 25.0%), SMAD4 (1 patient, 8.3%) and CDKN2A (1 patient, 8.3%). These findings indicated that the genomic mutations identified in tumor-derived DNA from IPWF samples of patients with PDAC with a CY(-) status who intend to undergo curative resection are potential biomarkers for predicting the recurrence of early peritoneal dissemination.

Marker selection strategies for circulating tumor DNA guided by phylogenetic inference

Motivation

Blood-based profiling of tumor DNA ("liquid biopsy") has offered great prospects for non-invasive early cancer diagnosis, treatment monitoring, and clinical guidance, but require further advances in computational methods to become a robust quantitative assay of tumor clonal evolution. We propose new methods to better characterize tumor clonal dynamics from circulating tumor DNA (ctDNA), through application to two specific questions: 1) How to apply longitudinal ctDNA data to refine phylogeny models of clonal evolution, and 2) how to quantify changes in clonal frequencies that may be indicative of treatment response or tumor progression. We pose these questions through a probabilistic framework for optimally identifying maximum likelihood markers and applying them to characterizing clonal evolution.

Results

We first estimate a distribution over plausible clonal lineage models, using bootstrap samples over pre-treatment tissue-based sequence data. We then refine these lineage models and the clonal frequencies they imply over successive longitudinal samples. We use the resulting framework for modeling and refining tree distributions to pose a set of optimization problems to select ctDNA markers to maximize measures of utility capturing ability to solve the two questions of reducing uncertain in phylogeny models or quantifying clonal frequencies given the models. We tested our methods on synthetic data and showed them to be effective at refining distributions of tree models and clonal frequencies so as to minimize measures of tree distance relative to the ground truth. Application of the tree refinement methods to real tumor data further demonstrated their effectiveness in refining a clonal lineage model and assessing its clonal frequencies. The work shows the power of computational methods to improve marker selection, clonal lineage reconstruction, and clonal dynamics profiling for more precise and quantitative assays of tumor progression.

Availability

https://github.com/CMUSchwartzLab/Mase-phi.git.

Contact

russells@andrew.cmu.edu.

Tumorigenic and tumoricidal properties of exosomes in cancers; a forward look

In recent decades, emerging data have highlighted the critical role of extracellular vesicles (EVs), especially (exosomes) Exos, in the progression and development of several cancer types. These nano-sized vesicles are released by different cell lineages within the cancer niche and maintain a suitable platform for the interchange of various signaling molecules in a paracrine manner. Based on several studies, Exos can transfer oncogenic factors to other cells, and alter the activity of immune cells, and tumor microenvironment, leading to the expansion of tumor cells and metastasis to the remote sites. It has been indicated that the cell-to-cell crosstalk is so complicated and a wide array of factors are involved in this process. How and by which mechanisms Exos can regulate the behavior of tumor cells and non-cancer cells is at the center of debate. Here, we scrutinize the molecular mechanisms involved in the oncogenic behavior of Exos released by different cell lineages of tumor parenchyma. Besides, tumoricidal properties of Exos from various stem cell (SC) types are discussed in detail.

Extracellular vesicles associated microRNAs: Their biology and clinical significance as biomarkers in gastrointestinal cancers

Gastrointestinal (GI) cancers, including colorectal, gastric, esophageal, pancreatic, and liver, are associated with high mortality and morbidity rates worldwide. One of the underlying reasons for the poor survival outcomes in patients with these malignancies is late disease detection, typically when the tumor has already advanced and potentially spread to distant organs. Increasing evidence indicates that earlier detection of these cancers is associated with improved survival outcomes and, in some cases, allows curative treatments. Consequently, there is a growing interest in the development of molecular biomarkers that offer promise for screening, diagnosis, treatment selection, response assessment, and predicting the prognosis of these cancers. Extracellular vesicles (EVs) are membranous vesicles released from cells containing a repertoire of biological molecules, including nucleic acids, proteins, lipids, and carbohydrates. MicroRNAs (miRNAs) are the most extensively studied non-coding RNAs, and the deregulation of miRNA levels is a feature of cancer cells. EVs miRNAs can serve as messengers for facilitating interactions between tumor cells and the cellular milieu, including immune cells, endothelial cells, and other tumor cells. Furthermore, recent years have witnessed considerable technological advances that have permitted in-depth sequence profiling of these small non-coding RNAs within EVs for their development as promising cancer biomarkers -particularly non-invasive, liquid biopsy markers in various cancers, including GI cancers. Herein, we summarize and discuss the roles of EV-associated miRNAs as they play a seminal role in GI cancer progression, as well as their promising translational and clinical potential as cancer biomarkers as we usher into the area of precision oncology.

Prospective Evaluation of Circulating Tumor DNA using Next Generation Sequencing as a Biomarker during Neoadjuvant Chemotherapy in Localized Pancreatic Cancer

OBJECTIVE

In this prospective study, we aim to characterize the prognostic value of circulating tumor DNA (ctDNA) by next-generation-sequencing (NGS) in patients undergoing neoadjuvant chemotherapy (NAC) for pancreatic ductal adenocarcinoma (PDAC).

SUMMARY BACKGROUND DATA

Circulating tumor DNA is a promising blood-based biomarker that is prognostic in several malignancies. Detection of ctDNA by NGS may provide insights regarding the mutational profiles in PDAC to help guide clinical decisions for patients in a potentially curative setting. However, the utility of ctDNA as a biomarker in localized PDAC remains unclear.

METHODS

Patients with localized PDAC were enrolled in a prospective study at Northwestern Medicine between October 2020 and October 2022. Blood samples were collected to perform targeted tumor agnostic NGS utilizing the Tempus x|F 105 gene panel at three timepoints: pre-therapy (at diagnosis), post-NAC, and after local therapy, including surgery. The relationship between ctDNA detection and CA19-9, and the prognostic significance of ctDNA detection were analyzed.

RESULTS

56 patients were included in the analysis. ctDNA was detectable in 48% at diagnosis, 33% post-NAC, and 41% after local therapy. After completion of NAC, patients with detectable ctDNA had higher CA19-9 levels versus those without (78.4 vs. 30.0, P=0.02). The presence of baseline ctDNA was associated with a CA19-9 response; those without ctDNA had a significant CA19-9 response following NAC (109.0 U/mL vs. 31.5 U/mL; P=0.01), while those with ctDNA present at diagnosis did not (198.1 U/mL vs. 113.8 U/mL; P=0.77). In patients treated with NAC, the presence of KRAS ctDNA at diagnosis was associated with and independently predicted worse progression-free-survival.

CONCLUSION

This report demonstrates the prognostic value of ctDNA analysis with NGS in localized PDAC. NGS ctDNA is a biomarker of treatment response to NAC. KRAS ctDNA at diagnosis independently predicts worse survival in patients treated with NAC.

Fast, sensitive, and specific multiplexed single-molecule detection of circulating tumor DNA

Circulating tumor DNA (ctDNA) analysis has emerged as a highly promising non-invasive assay for detection and monitoring of cancer. However, identification of multiple point-mutant ctDNAs, particularly at extremely low frequencies in early cancer stages, remains a significant challenge. To address this issue, we present a multiplexed ctDNA detection technique, SIMUL (single-molecule detection of multiple low-frequency mutations). SIMUL involves an unbiased preamplification of both wild-type and mutant DNAs, followed by the detection of mutant DNAs through single-molecule multicolor imaging. SIMUL enables highly sensitive and specific detection of multiple single-nucleotide mutations in a short span of time, even in the presence of 10,000-fold excess of wild-type DNA. Importantly, SIMUL can accurately measure mutant fractions due to its linear correlation between the number of single-molecule spots and the variant allele frequency. This breakthrough technique holds immense potential for clinical applications, offering significant improvements for example in early cancer detection and accurate evaluation of anticancer treatment responses.

Multiomic Approaches for Cancer Biomarker Discovery in Liquid Biopsies: Advances and Challenges

Cancer is a complex and heterogeneous disease that poses a significant threat to global health. Early diagnosis and treatment are critical for improving patient outcomes, and the use of liquid biopsies has emerged as a promising approach for cancer detection and monitoring. Traditionally, cancer diagnosis has relied on invasive tissue biopsies, the collection of which can prove challenging for patients and the results of which may not always provide accurate results due to tumor heterogeneity. Liquid biopsies have gained increasing attention as they provide a non-invasive and accessible source of cancer biomarkers, which can be used to diagnose cancer, monitor treatment response, and detect relapse. The integration of -omics technologies, such as proteomics, genomics, and metabolomics, has further enhanced the capabilities of liquid biopsies by introducing precision oncology and enabling the tailoring of treatment for individual patients based on their unique tumor biology. In this review, we will discuss the challenges and advances in the field of cancer liquid biopsies and the integration of -omics technologies for different types of liquid biopsies, including blood, tear, urine, sweat, saliva, and cerebrospinal fluid.

Designing and Validation of a Droplet Digital PCR Procedure for Diagnosis and Accurate Quantification of Nervous Necrosis Virus in the Mediterranean Area

The viral nervous necrosis virus (VNNV) is the causative agent of an important disease affecting fish species cultured worldwide. Early and accurate diagnosis is, at present, the most effective control and prevention tool, and molecular techniques have been strongly introduced and accepted by official organizations. Among those, real-time quantitative polymerase chain reaction (rt-qPCR) is nowadays displacing other molecular techniques. However, another PCR-based technology, droplet digital PCR (ddPCR), is on the increase. It has many advantages over qPCR, such as higher sensitivity and more reliability of the quantification. Therefore, we decided to design and validate a protocol for the diagnosis and quantification of SJ and RG type VNNV using reverse transcription-ddPCR (RT-ddPCR). We obtained an extremely low limit of detection, 10- to 100-fold lower than with RT-qPCR. Quantification by RT-ddPCR, with a dynamic range of 6.8-6.8 × 104 (SJ type) or 1.04 × 101-1.04 × 105 (RG type) cps/rctn, was more reliable than with RT-qPCR. The procedure was tested and validated in field samples, providing high clinical sensitivity and negative predictive values. In conclusion, we propose this method to substitute RT-qPCR protocols because it exceeds the expectations of qPCR in the diagnosis and quantification of VNNV.

Assessments of TP53 and CTNNB1 gene hotspot mutations in circulating tumour DNA of hepatitis B virus-induced hepatocellular carcinoma

Background: Hepatitis B virus (HBV) infection is one of the major causes of chronic liver disease, which progresses from chronic hepatitis B (CHB) to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Early detection and laboratory-based screening of hepatocellular carcinoma are still major challenges. This study was undertaken to determine whether the cancer hallmark gene signatures that are released into circulation as circulating tumour DNA (ctDNA) can be used as a liquid biopsy marker for screening, early detection, and prognosis of HCC. Methods: A total of 130 subjects, including HBV-HCC (n = 80), HBV-cirrhotic and non-cirrhotic (n = 35), and healthy (n = 15) controls, were evaluated for TP53 and beta-catenin (CTNNB1) gene hotspot mutations in ctDNA by Sanger-based cycle sequencing and droplet digital PCR (ddPCR) assays. Mutation detection frequency, percentage mutant fractions, and their association with tumour stage, mortality, and smoking habits were determined. Results: Sanger-based cycle sequencing was carried out for 32 HCC patients. Predict SNP Tools analysis indicated several pathogenic driver mutations in the ctDNA sequence, which include p.D228N, p.C229R, p.H233R, p.Y234D, p.S240T, p.G245S, and p.R249M for TP53 gene exon 7 and p.S33T for CTNNB1 gene exon 3. The TP53 c.746G>T (p.R249M) mutation was detected predominately (25% cases) by sequencing, but there was no dominant mutation at position c.747G>T (p.R249S) that was reported for HBV-HCC patients. A dual-probe ddPCR assay was developed to determine mutant and wild-type copy numbers of TP53 (p.R249M and p.R249S) and CTNNB1 (p.S45P) and their percentage mutant fraction in all 130 subjects. The TP53 R249M and CTNNB1 S45P mutations were detected in 31.25% and 26.25% of HCC patients, respectively, with a high mutant-to-wild-type fraction percentage (1.81% and 1.73%), which is significant as compared to cirrhotic and non-cirrhotic patients. Poor survival was observed in HCC patients with combined TP53 and CTNNB1 gene driver mutations. The TP53 R249M mutation was also significantly (p < 0.0001) associated with smoking habits (OR, 11.77; 95% CI, 3.219-36.20), but not the same for the TP53 R249S mutation. Conclusion: Screening of ctDNA TP53 and CTNNB1 gene mutations by ddPCR may be helpful for early detection and identifying the risk of HCC progression.

Advancements and Technical Considerations for Extracellular Vesicle Isolation and Biomarker Identification in Glioblastoma

Extracellular vesicles (EVs) are membrane-bound particles released by all cells. Previous research has found that these microscopic vesicles contribute to intercellular signaling and communication. EVs carry a variety of cargo, including nucleic acids, proteins, metabolites, and lipids. The composition of EVs varies based on cell of origin. Therefore, EVs can serve as an important biomarker in the diagnosis and treatment of various cancers. EVs derived from glioblastoma (GBM) cells carry biomarkers, which could serve as the basis for a potential diagnostic strategy known as liquid biopsy. Multiple EV isolation techniques exist, including ultrafiltration, size exclusion chromatography, flow field-flow fractionation, sequential filtration, differential ultracentrifugation, and density-gradient ultracentrifugation. Recent and ongoing work aims to identify cellular markers to distinguish GBM-derived EVs from those released by noncancerous cells. Strategies include proteomic analysis of GBM EVs, identification of GBM-specific metabolites, and use of Food and Drug Administration-approved 5-aminolevulinic acid-an oral agent that causes fluorescence of GBM cells-to recognize GBM EVs in a patient's blood. In addition, accurately and precisely monitoring changes in EV cargo concentrations could help differentiate between pseudoprogression and GBM recurrence, thus preventing unnecessary surgical interventions.

Circulating Cell-Free Nucleic Acids as Biomarkers for Diagnosis and Prognosis of Pancreatic Cancer

A lack of reliable early diagnostic tools represents a major challenge in the management of pancreatic cancer (PCa), as the disease is often only identified after it reaches an advanced stage. This highlights the urgent need to identify biomarkers that can be used for the early detection, staging, treatment monitoring, and prognosis of PCa. A novel approach called liquid biopsy has emerged in recent years, which is a less- or non-invasive procedure since it focuses on plasmatic biomarkers such as DNA and RNA. In the blood of patients with cancer, circulating tumor cells (CTCs) and cell-free nucleic acids (cfNAs) have been identified such as DNA, mRNA, and non-coding RNA (miRNA and lncRNA). The presence of these molecules encouraged researchers to investigate their potential as biomarkers. In this article, we focused on circulating cfNAs as plasmatic biomarkers of PCa and analyzed their advantages compared to traditional biopsy methods.

Clinical significance of circulating-tumour DNA analysis by metastatic sites in pancreatic cancer

BACKGROUND

Liquid biopsy is an alternative to tissue specimens for tumour genotyping. However, the frequency of genomic alterations with low circulating-tumour DNA (ctDNA) shedding is shown in pancreatic ductal adenocarcinoma (PDAC). We, therefore, investigated the prevalence of KRAS mutations and ctDNA fraction by the metastatic site in patients with PDAC.

METHODS

This study enrolled previously treated PDAC patients from a plasma genomic profiling study; ctDNA analysis was performed using Guardant360 at disease progression before initiating subsequent treatment.

RESULTS

In 512 patients with PDAC, KRAS mutations were detected in 57%. The frequency of KRAS mutation in ctDNA differed depending on the metastatic organ; among patients with single-organ metastasis (n = 296), KRAS mutation detection rate was significantly higher in patients with metastasis to the liver (78%). In addition, the median maximum variant allele frequency (VAF) was higher with metastasis to the liver (1.9%) than with metastasis to the lungs, lymph nodes, peritoneum or with locally advanced disease (0.2%, 0.4%, 0.2% and 0.3%, respectively).

CONCLUSION

The prevalence of KRAS mutations and maximum VAF were higher in patients with metastasis to the liver than in those with metastasis to other sites. This study indicated the clinical utility of ctDNA analysis, especially in PDAC with liver metastases.

Peripheral and Portal Venous KRAS ctDNA Detection as Independent Prognostic Markers of Early Tumor Recurrence in Pancreatic Ductal Adenocarcinoma

BACKGROUND

KRAS circulating tumor DNA (ctDNA) has shown biomarker potential for pancreatic ductal adenocarcinoma (PDAC) but has not been applied in clinical routine yet. We aim to improve clinical applicability of ctDNA detection in PDAC and to study the impact of blood-draw site and time point on the detectability and prognostic role of KRAS mutations.

METHODS

221 blood samples from 108 PDAC patients (65 curative, 43 palliative) were analyzed. Baseline peripheral and tumor-draining portal venous (PV), postoperative, and follow-up blood were analyzed and correlated with prognosis.

RESULTS

Significantly higher KRAS mutant detection rates and copy numbers were observed in palliative compared to curative patients baseline blood (58.1% vs 24.6%; P = 0.002; and P < 0.001). Significantly higher KRAS mutant copies were found in PV blood compared to baseline (P < 0.05) samples. KRAS detection in pre- and postoperative and PV blood were significantly associated with shorter recurrence-free survival (all P < 0.015) and identified as independent prognostic markers. KRAS ctDNA status was also an independent unfavorable prognostic factor for shorter overall survival in both palliative and curative cohorts (hazard ratio [HR] 4.9, P = 0.011; HR 6.9, P = 0.008).

CONCLUSIONS

KRAS ctDNA detection is an independent adverse prognostic marker in curative and palliative PDAC patients-at all sites of blood draw and a strong follow-up marker. The most substantial prognostic impact was seen for PV blood, which could be an effective novel tool for identifying prognostic borderline patients-guiding future decision-making on neoadjuvant treatment despite anatomical resectability. In addition, higher PV mutant copy numbers contribute to an improved technical feasibility.

Efficient and accurate KRAS genotyping using digital PCR combined with melting curve analysis for ctDNA from pancreatic cancer patients

A highly sensitive and highly multiplexed quantification technique for nucleic acids is necessary to predict and evaluate cancer treatment by liquid biopsy. Digital PCR (dPCR) is a highly sensitive quantification technique, but conventional dPCR discriminates multiple targets by the color of the fluorescent dye of the probe, which limits multiplexing beyond the number of colors of fluorescent dyes. We previously developed a highly multiplexed dPCR technique combined with melting curve analysis. Herein, we improved the detection efficiency and accuracy of multiplexed dPCR with melting curve analysis to detect KRAS mutations in circulating tumor DNA (ctDNA) prepared from clinical samples. The mutation detection efficiency was increased from 25.9% of the input DNA to 45.2% by shortening the amplicon size. The limit of detection of mutation was improved from 0.41 to 0.06% by changing the mutation type determination algorithm for G12A, resulting in a limit of detection of less than 0.2% for all the target mutations. Then, ctDNA in plasma from pancreatic cancer patients was measured and genotyped. The measured mutation frequencies correlated well with those measured by conventional dPCR, which can measure only the total frequency of KRAS mutants. KRAS mutations were detected in 82.3% of patients with liver or lung metastasis, which was consistent with other reports. Accordingly, this study demonstrated the clinical utility of multiplex dPCR with melting curve analysis to detect and genotype ctDNA from plasma with sufficient sensitivity.

Vibrational spectroscopy – are we close to finding a solution for early pancreatic cancer diagnosis?

Pancreatic cancer (PC) is an aggressive and lethal neoplasm, ranking seventh in the world for cancer deaths, with an overall 5-year survival rate of below 10%. The knowledge about PC pathogenesis is rapidly expanding. New aspects of tumor biology, including its molecular and morphological heterogeneity, have been reported to explain the complicated “cross-talk” that occurs between the cancer cells and the tumor stroma or the nature of pancreatic ductal adenocarcinoma-associated neural remodeling. Nevertheless, currently, there are no specific and sensitive diagnosis options for PC. Vibrational spectroscopy (VS) shows a promising role in the development of early diagnosis technology. In this review, we summarize recent reports about improvements in spectroscopic methodologies, briefly explain and highlight the drawbacks of each of them, and discuss available solutions. The important aspects of spectroscopic data evaluation with multivariate analysis and a convolutional neural network methodology are depicted. We conclude by presenting a study design for systemic verification of the VS-based methods in the diagnosis of PC.

The Role of Cell-Free DNA in Cancer Treatment Decision Making

The aim of this review is to evaluate the present status of the use of cell-free DNA and its fraction of circulating tumor DNA (ctDNA) because this year July 2022, an ESMO guideline was published regarding the application of ctDNA in patient care. This review is for clinical oncologists to explain the concept, the terms used, the pros and cons of ctDNA; thus, the technical aspects of the different platforms are not reviewed in detail, but we try to help in navigating the current knowledge in liquid biopsy. Since the validated and adequately sensitive ctDNA assays have utility in identifying actionable mutations to direct targeted therapy, ctDNA may be used for this soon in routine clinical practice and in other different areas as well. The cfDNA fragments can be obtained by liquid biopsy and can be used for diagnosis, prognosis, and selecting among treatment options in cancer patients. A great proportion of cfDNA comes from normal cells of the body or from food uptake. Only a small part (<1%) of it is related to tumors, originating from primary tumors, metastatic sites, or circulating tumor cells (CTCs). Soon the data obtained from ctDNA may routinely be used for finding minimal residual disease, detecting relapse, and determining the sites of metastases. It might also be used for deciding appropriate therapy, and/or emerging resistance to the therapy and the data analysis of ctDNA may be combined with imaging or other markers. However, to achieve this goal, further clinical validations are inevitable. As a result, clinicians should be aware of the limitations of the assays. Of course, several open questions are still under research and because of it cfDNA and ctDNA testing are not part of routine care yet.

Liquid Biopsy-Guided Interventional Oncology: A Proof of Concept with a Special Focus on Radiotherapy and Radiology

Although the role of liquid biopsy (LB) to measure minimal residual disease (MRD) in the treatment of epithelial cancer is well known, the biology of the change in the availability of circulating biomarkers arising throughout treatments such as radiotherapy and interventional radio-oncology is less explained. Deep knowledge of how therapeutic effects can influence the biology of the release mechanism at the base of the biomarkers available in the bloodstream is needed for selecting the appropriate treatment-induced tumor circulating biomarker. Combining existing progress in the LB and interventional oncology (IO) fields, a proof of concept is provided, discussing the advantages of the traditional risk assessment of relapsing lesions, limitations, and the timing of detection of the circulating biomarker. The current review aims to help both interventional radiologists and interventional radiation oncologists evaluate the possibility of drawing a tailor-made board of blood-based surveillance markers to reveal subclinical diseases and avoid overtreatment.

Skin Cancer Research Goes Digital: Looking for Biomarkers within the Droplets

Skin cancer, which includes the most frequent malignant non-melanoma carcinomas (basal cell carcinoma, BCC, and squamous cell carcinoma, SCC), along with the difficult to treat cutaneous melanoma (CM), pose important worldwide issues for the health care system. Despite the improved anti-cancer armamentarium and the latest scientific achievements, many skin cancer patients fail to respond to therapies, due to the remarkable heterogeneity of cutaneous tumors, calling for even more sophisticated biomarker discovery and patient monitoring approaches. Droplet digital polymerase chain reaction (ddPCR), a robust method for detecting and quantifying low-abundance nucleic acids, has recently emerged as a powerful technology for skin cancer analysis in tissue and liquid biopsies (LBs). The ddPCR method, being capable of analyzing various biological samples, has proved to be efficient in studying variations in gene sequences, including copy number variations (CNVs) and point mutations, DNA methylation, circulatory miRNome, and transcriptome dynamics. Moreover, ddPCR can be designed as a dynamic platform for individualized cancer detection and monitoring therapy efficacy. Here, we present the latest scientific studies applying ddPCR in dermato-oncology, highlighting the potential of this technology for skin cancer biomarker discovery and validation in the context of personalized medicine. The benefits and challenges associated with ddPCR implementation in the clinical setting, mainly when analyzing LBs, are also discussed.

Liquid Biopsy and Artificial Intelligence as Tools to Detect Signatures of Colorectal Malignancies: A Modern Approach in Patient's Stratification

Colorectal cancer (CRC) is the second most frequently diagnosed type of cancer and a major worldwide public health concern. Despite the global efforts in the development of modern therapeutic strategies, CRC prognosis is strongly correlated with the stage of the disease at diagnosis. Early detection of CRC has a huge impact in decreasing mortality while pre-lesion detection significantly reduces the incidence of the pathology. Even though the management of CRC patients is based on robust diagnostic methods such as serum tumor markers analysis, colonoscopy, histopathological analysis of tumor tissue, and imaging methods (computer tomography or magnetic resonance), these strategies still have many limitations and do not fully satisfy clinical needs due to their lack of sensitivity and/or specificity. Therefore, improvements of the current practice would substantially impact the management of CRC patients. In this view, liquid biopsy is a promising approach that could help clinicians screen for disease, stratify patients to the best treatment, and monitor treatment response and resistance mechanisms in the tumor in a regular and minimally invasive manner. Liquid biopsies allow the detection and analysis of different tumor-derived circulating markers such as cell-free nucleic acids (cfNA), circulating tumor cells (CTCs), and extracellular vesicles (EVs) in the bloodstream. The major advantage of this approach is its ability to trace and monitor the molecular profile of the patient's tumor and to predict personalized treatment in real-time. On the other hand, the prospective use of artificial intelligence (AI) in medicine holds great promise in oncology, for the diagnosis, treatment, and prognosis prediction of disease. AI has two main branches in the medical field: (i) a virtual branch that includes medical imaging, clinical assisted diagnosis, and treatment, as well as drug research, and (ii) a physical branch that includes surgical robots. This review summarizes findings relevant to liquid biopsy and AI in CRC for better management and stratification of CRC patients.

Smartphone-Based Pure DNAzyme Hydrogel Platform for Visible and Portable Colorimetric Detection of Cell-Free DNA

Cell-free DNA (cfDNA), as a tumor marker, is of great importance for the diagnosis of cancer and targeted therapy. However, the need for huge analytical instruments for cfDNA analysis has restricted its practical applications, especially in rural areas and third-world countries. Herein, a portable and visual smartphone-based DNAzyme hydrogel platform is developed for cfDNA detection. The target cfDNA triggers rolling circle amplification to produce a G-quadruplex-comprised DNA hydrogel with an horseradish peroxidase (HRP)-like catalytic function, which further catalyzes the chromogenic substrate to generate a visible output signal. Notably, the naked-eye detection of cfDNA can be realized by the macroscale visibility and catalytic ability of the DNA hydrogel. The linear range of the DNAzyme hydrogel platform for cfDNA detection is 0.1 pM-1500 nM with a detection limit of 0.042 pM. Moreover, this platform is exploited for the detection of cfDNA in spiked human serum with favorable sensitivity and recovery. Therefore, the DNAzyme hydrogel platform provides highly promising potential for testing other nucleic acid biomarkers.

Circulating tumor DNA methylation marker MYO1-G for diagnosis and monitoring of colorectal cancer

BACKGROUND

Circulating tumor DNA (ctDNA) is a promising diagnostic and prognostic marker for many cancers and has been actively investigated in recent years. Previous studies have already demonstrated the potential use of ctDNA methylation markers in the diagnosis and prognostication of colorectal cancer (CRC). This retrospective study validated the value of methylation biomarker MYO1-G (cg10673833) in CRC diagnosis and disease monitoring using digital droplet PCR (ddPCR), a biomarker selected from our previous study due to its highest diagnostic efficiency.

METHODS

Blood samples of CRC and control samples from tumor-free individuals at two institutions were collected to quantify the methylation ratio using ddPCR. Area under curve (AUC) was calculated after constructing receiver operating characteristic curve (ROC) for CRC diagnosis. Sensitivity and specificity were estimated and comparisons of methylation ratio in different groups were performed.

RESULTS

We collected 673 blood samples from 272 patients diagnosed with stage I-IV CRC and 402 normal control samples. The methylation biomarker discriminated patients with CRC from normal controls with high accuracy (area under curve [AUC] = 0.94) and yielded a sensitivity of 84.3% and specificity of 94.5%. Besides, methylation ratio of MYO1-G was associated with tumor burden and treatment response. The methylation ratio was significantly lower in patients after their radical operation than when compared with those before surgeries (P < 0.001). Methylation ratio was significantly higher in patients with disease progression than those with stable disease (P = 0.002) and those with complete response or partial response (P = 0.009).

CONCLUSIONS

Together, our study indicated that this methylation marker can serve as a potential biomarker for diagnosing and monitoring CRC.

ZnSe nanodisks:Ti3C2 MXenes-modified electrode for nucleic acid liquid biopsy with photoelectrochemical strategy

ZnSe nanodisks:Ti₃C₂ MXene complex was prepared for the first time. Based on its remarkable photoelectrochemical performance, combined with the enzyme-free toehold-mediated strand displacement reaction, a photoelectrochemical biosensor for the detection of the non-small-cell cancer biomarker ctDNA KRAS G12D was developed. ZnSe nanodisks were in situ grown on Ti₃C₂ MXene surface by two-step hydrothermal method. The high conductivity and adjustable band gap of MXene significantly enhanced the photoelectric response of ZnSe. Subsequently, the photoelectrochemical biosensor was prepared by combining with the signal amplification function of p-aminophenol and the enzyme-free toehold-mediated strand displacement reaction on the modified ITO electrode surface. Under the optimized conditions, the linear detection range is 0.5 ~ 100.0 fM, and the detection limit is 0.2 fM, which realizes the sensitive detection of KRAS G12D. The photoelectrochemical biosensor constructed opens up a new pathway for the preparation of new Mxene-based composite materials and the research of photoelectrochemical biosensor. Nucleic acid liquid biopsy with ZnSe nanodisks:Ti₃C₂ MXene photoelectroactive modified electrode.

Pipette-Tip-Enabled Digital Nucleic Acid Analyzer for COVID-19 Testing with Isothermal Amplification

Herein, a pipette-tip-enabled digital nucleic acid analyzer for high-performance COVID-19 testing is demonstrated. This is achieved by digital loop-mediated isothermal amplification (digital LAMP or dLAMP) using common laboratory equipment and materials. It is shown that simply fixing a glass capillary inside conventional pipette tips enables the generation of monodisperse, water-in-oil microdroplets with benchtop centrifugation. It is shown that using LAMP, the ORF1a/b gene, a standard test region for COVID-19 screening, can be amplified without a thermal cycler. The amplification allows counting of fluorescent microdroplets so that Poisson analysis can be performed to allow quantification with a limit of detection that is 1 order of magnitude better than those of nondigital techniques and comparable to those of commercial dLAMP platforms. It is envisioned that this work will inspire studies on ultrasensitive digital nucleic acid analyzers demanding both sensitivity and accessibility, which is pivotal to their large-scale applications.

Liquid Biopsy to Detect Minimal Residual Disease: Methodology and Impact

One reason why some patients experience recurrent disease after a curative-intent treatment might be the persistence of residual tumor cells, called minimal residual disease (MRD). MRD cannot be identified by standard radiological exams or clinical evaluation. Tumor-specific alterations found in the blood indirectly diagnose the presence of MRD. Liquid biopsies thus have the potential to detect MRD, allowing, among other things, the detection of circulating tumor DNA (ctDNA), circulating tumor cells (CTC), or tumor-specific microRNA. Although liquid biopsy is increasingly studied, several technical issues still limit its clinical applicability: low sensitivity, poor standardization or reproducibility, and lack of randomized trials demonstrating its clinical benefit. Being able to detect MRD could give clinicians a more comprehensive view of the risk of relapse of their patients and could select patients requiring treatment escalation with the goal of improving cancer survival. In this review, we are discussing the different methodologies used and investigated to detect MRD in solid cancers, their respective potentials and issues, and the clinical impacts that MRD detection will have on the management of cancer patients.

Role of Circulating Tumor DNA in Gastrointestinal Cancers: Current Knowledge and Perspectives

Gastrointestinal (GI) cancers are major health burdens worldwide and biomarkers are needed to improve the management of these diseases along their evolution. Circulating tumor DNA (ctDNA) is a promising non-invasive blood and other bodily-fluid-based biomarker in cancer management that can help clinicians in various cases for the detection, diagnosis, prognosis, monitoring and personalization of treatment in digestive oncology. In addition to the well-studied prognostic role of ctDNA, the main real-world applications appear to be the assessment of minimal residual disease to further guide adjuvant therapy and predict relapse, but also the monitoring of clonal evolution to tailor treatments in metastatic setting. Other challenges such as predicting response to treatment including immune checkpoint inhibitors could also be among the potential applications of ctDNA. Although the level of advancement of ctDNA development in the different tumor localizations is still inhomogeneous, it might be now reliable enough to be soon used in clinical routine for colorectal cancers and shows promising results in other GI cancers.