Circulating Tumor DNA is Unreliable to Detect Somatic Gene Alterations in Gastrointestinal Peritoneal Carcinomatosis

The Role of Prophylactic or Adjuvant Hyperthermic Intraperitoneal Therapy in Appendiceal and Colorectal Cancer Peritoneal Metastasis

Appendiceal neoplasms and colorectal cancer have a propensity to develop peritoneal metastases. Despite advancements in systemic therapy and surgical management, the development and management of peritoneal metastases remains a challenging problem. Utilization of adjuvant or prophylactic hyperthermic intraperitoneal chemotherapy has been described, with varying quality of data and reported outcomes. The utilization of prophylactic or adjuvant hyperthermic intraperitoneal chemotherapy in patients with appendiceal neoplasms and colorectal cancer remains an active area of exploration.

Japan society of clinical oncology position paper on appropriate clinical use of molecular residual disease (MRD) testing

Although the 5-year relative survival rates for resectable solid tumors have improved over the past few years, the risk of postoperative recurrence necessitates effective monitoring strategies. Recent advancements in molecular residual disease (MRD) testing based on circulating tumor DNA (ctDNA) analysis have shown considerable promise in the context of predicting recurrence; however, significant barriers to widespread clinical implementation remain-mainly, low awareness among healthcare professionals, high costs, and lack of standardized assays and comprehensive evidence. This position paper, led by the Japan Society of Clinical Oncology, aims to establish a common framework for the appropriate clinical use of MRD testing in a tumor type-agnostic manner. It synthesizes currently available evidence, reviews region-specific clinical trends, addresses critical clinical questions related to MRD testing, and offers recommendations to guide healthcare professionals, biotechnology and pharmaceutical companies, and regulatory authorities. These recommendations were developed based on a voting process involving 15 expert members, ensuring a consensus-driven approach. These findings underscore the importance of collaborative efforts among various stakeholders in enhancing the clinical utility of MRD testing. This project aimed to foster consensus and provide clear guidelines to support the advancement of precision medicine in oncology and improve patient outcomes in the context of perioperative care.

Circulating tumor DNA in colorectal cancer: biology, methods and applications

In the practice of colorectal cancer (CRC), traditional tumor tissue analysis is limited by intratumoral and intertumoral heterogeneity and its invasive nature. Circulating tumor DNA (ctDNA) analysis, a promising liquid biopsy approach, has been increasingly explored in clinical studies. Biologically, ctDNA is characterized by tumor-specific diversity and rapid clearance from circulation, enabling real-time, dynamic, and repeatable assessments. Technologically, PCR- and NGS-based downstream analysis methods have been developed and validated. However, variables in pre-analytical and analytical procedures underscores the need for standardized protocols. Compared with clinicopathology-based risk stratification, ctDNA-based molecular residual disease detection has demonstrated significant potential in guiding treatment decisions. Qualitative and quantitative changes in ctDNA have also shown predictive and prognostic value during neoadjuvant or adjuvant treatment, as well as in later-line treatment for metastatic CRC. Specific molecular aberrations in ctDNA can not only assist in identifying candidates for targeted therapies but also reveal resistance mechanisms. Additionally, emerging research is exploring the potential of ctDNA in early cancer detection. Overall, as a novel biomarker, ctDNA holds substantial promise in advancing clinical practice. This review focuses on the biological characteristics, pre-analytical variables, and downstream analysis methods of ctDNA and summarizes its role across various clinical scenarios in CRC.

Incorporating Circulating Tumor DNA Testing Into Clinical Trials: A Position Paper by the National Cancer Institute GI Oncology Circulating Tumor DNA Working Group

PURPOSE

Circulating tumor DNA (ctDNA) is an emerging tool in the evaluation of GI cancers. Challenges remain in defining its utility and role as a primary end point in therapeutic trials. The National Cancer Institute (NCI) ctDNA GI working group was created to evaluate current data and provide guidance on the inclusion of ctDNA in GI cancer trials.

METHODS

The NCI GI steering committee assigned four task force members to serve as co-chairs for the working group. Co-chairs identified experts within each GI disease group to form a panel that convened to review data and provide recommendations. The group focused on ctDNA's role as a potential surrogate for assessing prognosis and guiding treatment decisions that may enhance GI cancer trials. A manuscript was drafted, circulated, revised, and voted on by the panel. The final draft was reviewed by the Cancer Therapy Evaluation Program.

RESULTS

Further data are required to support ctDNA as a primary end point for late-phase therapeutic trials, particularly in studies that could change the standard-of-care. However, the group supports ctDNA as a primary efficacy end point for phase II studies and as a noninvasive evaluation strategy for new drug development. Incorporation of ctDNA as a biomarker in trial design must consider the specific context of disease biology of the GI cancer subtypes. ctDNA should be incorporated as an exploratory end point across a variety of disease settings and indications. Several practical considerations were identified to optimize the incorporation of ctDNA in future trial design.

CONCLUSION

Prospective trials are required to clarify the role of ctDNA as a valid surrogate end point for progression-free or overall survival in GI cancers.

Educational Review: Updates on Therapeutic Strategies for Gastric Cancer with Peritoneal Metastasis

Gastric cancer (GC) commonly presents in advanced stages with metastatic spread to the peritoneal cavity, and outcomes associated with gastric cancer with peritoneal metastasis (GCPM) continue to carry a dismal prognosis. Persistent challenges in the detection of peritoneal metastasis (PM) have resulted in a relative paucity of high-quality data to inform management decisions. Several consensus groups have published recommendations to guide management, including most recently the National Comprehensive Cancer Network guidelines, which now include cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) as a potential treatment modality in select patients with GCPM. Multiple clinical trials have investigated the use of CRS/HIPEC and other peritoneal-directed therapies, such as intraperitoneal chemotherapy (IPC) and pressurized intraperitoneal aerosolized chemotherapy (PIPAC). As high-volume centers work to incorporate such therapies into their practice, ongoing clinical trials are aimed at understanding their efficacy. Recent findings have improved understanding of the mechanisms and pathophysiology underlying GCPM while the discovery of novel targets offers potential for drug development and therapeutic strategies to overcome treatment resistance. This review highlights recent advancements and addresses the persistent challenges in managing GCPM while also offering a comprehensive summary of current guidelines and treatment strategies.

Management of Peritoneal Metastasis in Patients with Pancreatic Ductal Adenocarcinoma

The peritoneum is the second most common site of metastasis in patients with pancreatic ductal adenocarcinoma (PDAC). Up to half of all patients that undergo curative-intent resection eventually develop peritoneal metastasis (PM), which accounts for significant morbidity and drives mortality. Despite recent advances in management, PM is associated with very poor prognosis, which is often measured in weeks to months. Clinical manifestations including bowel obstruction, ascites, and urinary obstruction have profound impact on quality of life. Even with relatively advanced disease, PM often remains occult on imaging and thus tend to be underdiagnosed and understudied. Many patients with peritoneal-only PM are excluded from clinical trials because response cannot be measured by standard radiographic criteria. Furthermore, as patients with PM are not eligible for surgical resection and low-volume peritoneal disease is often not amenable to percutaneous biopsy, tissue samples for peritoneal-specific translational studies are limited. Intraperitoneal therapeutics have been proposed as an attractive option for PM, as better penetration of tumor tissue can be achieved with less systemic toxicity compared with intravenous chemotherapy. Heated intraperitoneal chemotherapy (HIPEC), typically combined with cytoreductive surgery (CRS), is an option for select patients with PM from gynecologic or gastrointestinal primary, and for patients with primary peritoneal mesothelioma. However, the incorporation of locoregional therapy for PM in patients with PDAC has been poorly studied given the aggressive nature of pancreatic cancer and overall poor prognosis. With recent advances in existing treatment options, there may be a subset of patients who may derive benefits from locoregional control with cytoreduction and/or intraperitoneal chemotherapy. Critically, additional work is needed to determine PM-favorable clinical and tumoral predictive biomarkers to identify patients who may benefit from a more aggressive approach. We describe the current state of management of patients with peritoneal metastasis from PDAC and review the available data exploring peritoneal-directed therapy with cytoreductive surgery and/or intraperitoneal chemotherapy.

Peritoneal Tumour DNA in Peritoneal Fluid: Emerging Tool for Peritoneal Metastasis Detection

The prognostic significance of positive peritoneal cytology still varied between cancer types and geographical origin. However, because of the lack of sensitivity of this biomarker, conventional cytology is not routinely performed in every country. Here, we wanted to test a new biomarker, peritoneal tumour DNA, using NGS technique, in order to compare it with the historical one, in patients having peritoneal metastases of gastrointestinal or ovarian cancer.

Undetectable circulating tumor DNA confirms the inability of pseudomyxoma peritonei to systemic dissemination

The study of circulating tumor DNA (ctDNA) plays a pivotal role in advancing precision oncology, providing valuable information for individualized patient care and contributing to the ongoing effort to improve cancer diagnosis, treatment, and management. However, its applicability in pseudomyxoma peritonei (PMP) remains unexplored. In this multicenter retrospective study involving 21 PMP patients, we investigated ctDNA presence in peripheral blood using three distinct methodologies. Despite mucinous tumor tissues exhibiting KRAS and GNAS mutations, ctDNA for these mutations was undetectable in blood samples. In this pilot study, circulating tumor DNA was not detected in blood when the tumor harbored mutations of known significance. In the future, a study with a larger sample size is needed to confirm these findings and to determine whether ctDNA could identify patients at risk for early recurrence and/or systemic metastases.

Utility of Circulating Tumor DNA Assessment in Characterizing Recurrence Sites after Optimal Resection for Metastatic Colorectal Cancer

BACKGROUND

Plasma circulating tumor DNA (ctDNA) is a promising biomarker for metastatic colorectal cancer (mCRC); however, its role in characterizing recurrence sites after mCRC resection remains poorly understood. This single-institution study investigated the timing of ctDNA detection and its levels in the context of recurrence at different sites after mCRC resection.

STUDY DESIGN

Patients who underwent optimal resection of CRC metastases involving the peritoneum, distant lymph nodes, or liver, with serial postoperative tumor-informed ctDNA assessments (Signatera) were included. Recurrence sites, as defined by surveillance imaging or laparoscopy, were categorized as peritoneal-only and other distant sites (liver, lung, lymph nodes, or body wall).

RESULTS

Among the 31 included patients, ctDNA was detected in all 26 (83.4%) patients with postoperative recurrence and was persistently undetectable in 5 patients who did not experience recurrence. At 3 months postsurgery, ctDNA was detected in 2 (25%) of 8 patients with peritoneal-only recurrence and 17 (94.4%) of 18 patients with distant recurrence (p < 0.001). Beyond 3 months, ctDNA was detected in the remaining 6 patients with peritoneal-only disease and 1 patient with distant disease. ctDNA detection preceded the clinical diagnosis of recurrence by a median of 9 weeks in both groups. At recurrence, peritoneal-only recurrent cases exhibited lower ctDNA levels (median 0.4 mean tumor molecules/mL, interquartile range 0.1 to 0.8) compared with distant recurrence (median 5.5 mean tumor molecules/mL, interquartile range 0.8 to 33.3, p = 0.004).

CONCLUSIONS

Peritoneal-only recurrence was associated with delayed ctDNA detection and low levels of ctDNA after optimal resection for mCRC. ctDNA testing may effectively characterize recurrence sites and may help guide subsequent treatments specific to the disease sites involved.

Multi-Institutional Study Evaluating the Role of Circulating Tumor DNA in the Management of Appendiceal Cancers

PURPOSE

Conventional surveillance methods are poorly sensitive for monitoring appendiceal cancers (AC). This study investigated the utility of circulating tumor DNA (ctDNA) in evaluating systemic therapy response and recurrence after surgery for AC.

METHODS

Patients from two specialized centers who underwent tumor-informed ctDNA testing (Signatera) were evaluated to determine the association between systemic therapy and ctDNA detection. In addition, the accuracy of ctDNA detection during surveillance for the diagnosis of recurrence after complete cytoreductive surgery (CRS) for grade 2-3 ACs with peritoneal metastases (PM) was investigated.

RESULTS

In this cohort of 94 patients with AC, most had grade 2-3 tumors (84.0%) and PM (84.0%). Fifty patients completed the assay in the presence of identifiable disease, among which ctDNA was detected in 4 of 7 (57.1%), 10 of 16 (62.5%), and 19 of 27 (70.4%) patients with grade 1, 2, and 3 diseases, respectively. Patients who had recently received systemic chemotherapy had ctDNA detected less frequently (7 of 16 [43.8%] v 26 of 34 [76.5%]; odds ratio, 0.22 [95% CI, 0.06 to 0.82]; P = .02). Among 36 patients with complete CRS for grade 2-3 AC-PM, 16 (44.4%) developed recurrence (median follow-up, 19.6 months). ctDNA detection was associated with shorter recurrence-free survival (median 11.3 months v not reached; hazard ratio, 14.1 [95% CI, 1.7 to 113.8]; P = .01) and showed high accuracy for the detection of recurrence (sensitivity 93.8%, specificity 85.0%). ctDNA was more sensitive than carcinoembryonic antigen (62.5%), CA19-9 (25.0%), and CA125 (18.8%) and was the only elevated biomarker in four (25%) patients with recurrence.

CONCLUSION

This study revealed a reduced ctDNA detection frequency after systemic therapy and accurate recurrence assessment after CRS. These findings underscore the role of ctDNA as a predictive and prognostic biomarker for grade 2-3 AC-PM management.

Molecular Landscape and Therapeutic Strategies against Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. Although the overall incidence of CRC is decreasing, the incidence of young-onset CRC, characterized by a diagnosis of CRC before age 50, is increasing. Outcomes for CRC patients are improving, partly due to comprehensive molecular characterization of tumors and novel therapeutic strategies. Advances in genomic and transcriptomic analyses using blood- and tumor-tissue-based sequencing have facilitated identification of distinct tumor subtypes harboring unique biological characteristics and therapeutic vulnerabilities. These insights have led to the development and incorporation of targeted therapies and immunotherapy in CRC treatment. In this review, we discuss the molecular landscape and key oncogenes/tumor suppressors contributing to CRC tumorigenesis, metastasis, and therapeutic resistance. We also discuss personalized therapeutic strategies for subsets of CRC patients and provide an overview of evolving novel treatments being evaluated in clinical trials.

Exploring RAS mutation incidence and temporal heterogeneity in metastatic colorectal cancer patients - a single-institution experience utilising circulating tumour DNA

Introduction

Colorectal cancer (CRC) remains a significant global health challenge, ranking among the leading causes of neoplastic mortality. Despite transformative therapeutic advances, a considerable proportion of patients are diagnosed with metastatic disease, and 15-30% of those initially presenting with early-stage CRC eventually experience recurrence. Comprehensive molecular testing, especially the evaluation of microsatellite instability and mutations in KRAS/NRAS or BRAF genes, is essential upon diagnosis of stage IV disease, guiding treatment decisions.

Material and methods

This manuscript explores the mutational landscape of KRAS and NRAS in patients with CRC, employing digital polymerase chain reaction (PCR) BEAMing for the detection of mutations in liquid biopsy. Our study enrolled patients with histologically confirmed CRC and stage IV disease, focusing on identifying mutations in KRAS and NRAS genes during various stages of therapy.

Results

Evaluating baseline, midline, and progression samples, we found that 66.6% maintained consistent mutational status post-disease progression, while 33.3% exhibited a shift in mutational status. The application of techniques with high sensitivity, such as BEAMing Digital PCR, is pivotal for accurate circulating tumour DNA (ctDNA) mutation detection. The study underscores the significance of continuous molecular monitoring in guiding therapeutic decisions for patients with metastatic CRC.

Conclusions

Our findings contribute to our understanding of the evolving mutational landscape and the potential clinical implications of ctDNA ana- lysis in the era of personalised cancer medicine.

Normal CEA Levels After Neoadjuvant Chemotherapy and Cytoreduction with Hyperthermic Intraperitoneal Chemoperfusion Predict Improved Survival from Colorectal Peritoneal Metastases

BACKGROUND

Normal carcinoembryonic antigen (CEA) levels (≤ 2.5 ng/ml) after resection of localized colorectal cancer or liver metastases are associated with improved survival, however, these trends are understudied for colorectal peritoneal metastases (CRPM).

PATIENTS AND METHODS

We conducted a retrospective single-institution study of patients with CRPM undergoing cytoreductive surgery with hyperthermic intraperitoneal chemoperfusion (CRS/HIPEC) with and without neoadjuvant chemotherapy (NACT). CEA was measured before and after NACT and within 3 months after CRS/HIPEC.

RESULTS

A total of 253 patients (mean age 55.3 years) with CRPM undergoing CRS/HIPEC had complete CEA data and 191 also underwent NACT with complete data. The median peritoneal carcinomatosis index score (PCI) of the overall cohort was 12 and 82.7% of patients had complete cytoreduction (CC0). In total, 64 (33.5%) patients had normal CEA levels after NACT with a median overall survival (OS) of 45.2 months compared with those with an elevated CEA (26.4 months, p = 0.004). Patients with normal CEA after NACT had a lower PCI found at the time of surgery than those with elevated CEA (10 versus 14, p < 0.001), 68 (26.9%) patients with an elevated preoperative CEA level experienced normalization after CRS/HIPEC, and 118 (46.6%) patients had elevated CEA after CRS/HIPEC. Patients who experienced normalization demonstrated similar OS to patients that had normal CEA levels pre- and post-surgery and improved OS compared with those with elevated postop CEA (median 41.9 versus 47 months versus 17.1 months, respectively, p < 0.001).

CONCLUSIONS

Normal CEA levels after NACT and/or CRS/HIPEC are associated with improved survival for patients with CRPM. Patients that normalize CEA levels after surgery have similar survival to those with normal preoperative levels.

Circulating Tumor DNA (ctDNA) Clearance May Predict Treatment Response in Neoadjuvant Colorectal Cancer Management

Background: Circulating tumor DNA (ctDNA) is extracellular DNA released by tumors and has been proposed as a marker of residual disease as well as a predictor of disease recurrence in the adjuvant setting. However, data are lacking on the utility of this biomarker in the neoadjuvant setting. Methods: We performed a retrospective study of stage III and IV colorectal cancer patients receiving neoadjuvant treatment at a single institution. Results: Seventeen patients converted from a positive pre-neoadjuvant ctDNA to a negative ctDNA prior to surgery. Five patients remained persistently positive despite systemic treatment. ctDNA conversion was found to be associated with a higher incidence of favorable treatment effect scores on final surgical pathology. There was no difference in recurrence-free survival in this small population. Furthermore, no added benefit was identified for patients receiving additional neoadjuvant therapy after the time of positive to negative ctDNA conversion. Conclusions: This study highlights the potential utility of ctDNA and the need for prospective trials in the neoadjuvant setting to monitor treatment response and guide decisions on treatment duration.

Role of Circulating Tumor DNA Among Patients with Colorectal Peritoneal Metastases

PURPOSE

This was a review of circulating tumor DNA (ctDNA) in patients with peritoneal metastases from colorectal cancer.

METHODS

We searched the PubMed database for studies reporting detection of ctDNA in patients with colorectal cancer (CRC) and with peritoneal metastases (PM) from colorectal cancer (CRPM). We extracted data on the population included, number of subjects, study design, type of ctDNA assay used and schedule, and the major findings from these publications.

RESULTS

We identified 13 studies for review investigating ctDNA, using a variety of ctDNA assays, among 1787 patients with CRC without PM, as well as four eligible published and one unpublished (in press) studies, which included 255 patients with PM from any primary site and 61 patients with CRPM. Among the 13 studies investigating ctDNA among CRC without PM, posttreatment surveillance ctDNA was associated with recurrence and was generally more sensitive than imaging or tumor markers. Among the five studies including patients with PM, ctDNA was not universally able to detect the presence of PM, but when present, ctDNA predicted worse outcomes.

CONCLUSION

Circulating-tumor DNA is a potentially useful surveillance tool for patients with CRC. However, the sensitivity of ctDNA to detect CRPM is variable and warrants further inquiry.

Recurrence and Survival Following Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy for Synchronous and Metachronous Peritoneal Metastases of Colorectal Origin

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) has improved the 5-year survival for colorectal cancer (CRC) patients with peritoneal metastases (PM). Little is known about recurrence patterns and recurrence rates between synchronous (S) and metachronous (M) PM following CRS+HIPEC. We aimed to describe the recurrence patterns, overall survival (OS) and disease-free survival (DFS) in S-PM and M-PM patients after complete CRS+HIPEC. From June 2006 to December 2020, a prospective cohort study included 310 CRC patients, where 181 patients had S-PM (58.4%) and 129 patients had M-PM (41.6%). After a median 10.3-month follow-up, 247/310 (79.7%) patients experienced recurrence, and recurrence sites included isolated peritoneal (32.4%), multifocal (peritoneal and liver and/or lung(s)) (22.7%), isolated liver (17.8%), isolated lung (10.5%) and other (16.6%) sites. Recurrence patterns did not differ between S-PM and M-PM. M-PM patients had an impaired DFS compared to S-PM patients (9.4 months (95% CI: 7.3-12.1) vs. 12.5 months (95% CI: 11.2-13.9), p = 0.01). The median OS was similar for S-PM and M-PM (38.4 months (95% CI: 31.2-46.8) vs. 40.8 months (95% CI: 28.8-46.8), p = 0.86). Despite frequent recurrence at extraperitoneal locations, long-term survival was achievable after CRS+HIPEC in CRC patients with PM. The recurrence patterns and OS did not differ between groups, yet M-PM patients had a shorter DFS.

Current Applications and Challenges of Next-Generation Sequencing in Plasma Circulating Tumour DNA of Ovarian Cancer

Circulating tumour DNA (ctDNA) facilitates longitudinal study of the tumour genome, which, unlike tumour tissue biopsies, globally reflects intratumor and intermetastatis heterogeneity. Despite its costs, next-generation sequencing (NGS) has revolutionised the study of ctDNA, ensuring a more comprehensive and multimodal approach, increasing data collection, and introducing new variables that can be correlated with clinical outcomes. Current NGS strategies can comprise a tumour-informed set of genes or the entire genome and detect a tumour fraction as low as 10-5. Despite some conflicting studies, there is evidence that ctDNA levels can predict the worse outcomes of ovarian cancer (OC) in both early and advanced disease. Changes in those levels can also be informative regarding treatment efficacy and tumour recurrence, capable of outperforming CA-125, currently the only universally utilised plasma biomarker in high-grade serous OC (HGSOC). Qualitative evaluation of sequencing shows that increasing copy number alterations and gene variants during treatment may correlate with a worse prognosis in HGSOC. However, following tumour clonality and emerging variants during treatment poses a more unique opportunity to define treatment response, select patients based on their emerging resistance mechanisms, like BRCA secondary mutations, and discover potential targetable variants. Sequencing of tumour biopsies and ctDNA is not always concordant, likely as a result of clonal heterogeneity, which is better captured in the plasma samples than it is in a large number of biopsies. These incoherences may reflect tumour clonality and reveal the acquired alterations that cause treatment resistance. Cell-free DNA methylation profiles can be used to distinguish OC from healthy individuals, and NGS methylation panels have been shown to have excellent diagnostic capabilities. Also, methylation signatures showed promise in explaining treatment responses, including BRCA dysfunction. ctDNA is evolving as a promising new biomarker to track tumour evolution and clonality through the treatment of early and advanced ovarian cancer, with potential applicability in prognostic prediction and treatment selection. While its role in HGSOC paves the way to clinical applicability, its potential interest in other histological subtypes of OC remains unknown.

Circulating Tumor DNA and Management of Colorectal Cancer

Although the incidence of colorectal cancer (CRC) has decreased as a result of increased screening and awareness, it still remains a major cause of cancer-related death. Additionally, early detection of CRC recurrence by conventional means such as CT, endoscopy, and CEA has not translated into an improvement in survival. Liquid biopsies, such as the detection circulating tumor DNA (ctDNA), have been investigated as a biomarker for patients with CRC in terms of prognosis and recurrence, as well as their use to guide therapy. In this manuscript, we provide an overview of ctDNA as well as its utility in providing prognostic information, using it to guide therapy, and monitoring for recurrence in patients with CRC. In addition, we discuss the influence the site of disease may have on the ability to detect ctDNA in patients with metastatic CRC.

Peritoneal Cell-Free Tumor DNA is a Biomarker of Locoregional and Peritoneal Recurrence in Resected Pancreatic Ductal Adenocarcinomas

BACKGROUND

Recurrence after curative-intent pancreatectomy for pancreatic ductal adenocarcinomas (PDAC) is quite frequent with locoregional and peritoneal recurrence in about one-third of cases. We hypothesize that peritoneal cell-free tumor DNA (ptDNA) present in the intraoperative peritoneal lavage (PL) fluid may be used as a predictive biomarker of locoregional and peritoneal recurrence.

PATIENTS AND METHODS

Under institutional review board (IRB)-approved protocol, pre- and postresection PL fluids were collected from PDAC patients undergoing curative-intent pancreatectomy. PL fluids from PDAC patients with pathologically proven peritoneal metastasis were also collected as positive controls. Cell-free DNA was extracted from PL fluids. Droplet digital PCR (ddPCR) was performed using ddPCR KRAS G12/G13 screening kit. Recurrence-free survival (RFS) based on KRAS-mutant ptDNA level was determined using Kaplan-Meier methods.

RESULTS

KRAS-mutant ptDNA was detected in PL fluids from all PDAC patients. KRAS-mutant ptDNA was detected in 11/21 (52%) preresection and 15/18 (83%) postresection PL fluid samples. With a median follow-up of 23.6 months, 12 patients developed recurrence (8 locoregional/peritoneal recurrence, 9 pulmonary/hepatic recurrence); 5/8 (63%) and 6/6 (100%) patients with mutant allele frequency (MAF) of > 0.10% in pre- and postresection PL fluids, respectively, developed recurrence. Using a cutoff value of 0.10% MAF, the presence of KRAS-mutant ptDNA in postresection PL fluid predicted a significantly shortened time to locoregional and peritoneal recurrence (median RFS of 8.9 months versus not reached, P = 0.003).

CONCLUSIONS

This study suggests that ptDNA in postresection PL fluids may be a useful biomarker to predict locoregional and peritoneal recurrence in resected PDAC patients.

Liquid biopsies for cancer: From bench to clinic

Over the past two decades, liquid biopsy has been increasingly used as a supplement, or even, a replacement to the traditional biopsy in clinical oncological practice, due to its noninvasive and early detectable properties. The detections can be based on a variety of features extracted from tumor‑derived entities, such as quantitative alterations, genetic changes, and epigenetic aberrations, and so on. So far, the clinical applications of cancer liquid biopsy mainly aimed at two aspects, prediction (early diagnosis, prognosis and recurrent evaluation, therapeutic response monitoring, etc.) and intervention. In spite of the rapid development and great contributions achieved, cancer liquid biopsy is still a field under investigation and deserves more clinical practice. To better open up future work, here we systematically reviewed and compared the latest progress of the most widely recognized circulating components, including circulating tumor cells, cell-free circulating DNA, noncoding RNA, and nucleosomes, from their discovery histories to clinical values. According to the features applied, we particularly divided the contents into two parts, beyond epigenetics and epigenetic-based. The latter was considered as the highlight along with a brief overview of the advances in both experimental and bioinformatic approaches, due to its unique advantages and relatively lack of documentation.

Plasma Exosome Gene Signature Differentiates Colon Cancer from Healthy Controls

BACKGROUND

Liquid biopsies have become an integral part of cancer management as minimally invasive options to detect molecular and genetic changes. However, current options show poor sensitivity in peritoneal carcinomatosis (PC). Novel exosome-based liquid biopsies may provide critical information on these challenging tumors. In this initial feasibility analysis, we identified an exosome gene signature of 445 genes (ExoSig445) from colon cancer patients, including those with PC, that is distinct from healthy controls.

METHODS

Plasma exosomes from 42 patients with metastatic and non-metastatic colon cancer and 10 healthy controls were isolated and verified. RNAseq analysis of exosomal RNA was performed and differentially expressed genes (DEGs) were identified by the DESeq2 algorithm. The ability of RNA transcripts to discriminate control and cancer cases was assessed by principal component analysis (PCA) and Bayesian compound covariate predictor classification. An exosomal gene signature was compared with tumor expression profiles of The Cancer Genome Atlas.

RESULTS

Unsupervised PCA using exosomal genes with greatest expression variance showed stark separation between controls and patient samples. Using separate training and test sets, gene classifiers were constructed capable of discriminating control and patient samples with 100% accuracy. Using a stringent statistical threshold, 445 DEGs fully delineated control from cancer samples. Furthermore, 58 of these exosomal DEGs were found to be overexpressed in colon tumors.

CONCLUSIONS

Plasma exosomal RNAs can robustly discriminate colon cancer patients, including patients with PC, from healthy controls. ExoSig445 can potentially be developed as a highly sensitive liquid biopsy test in colon cancer.

Exosomes as a Source of Biomarkers for Gastrointestinal Cancers

Exosomes are small, lipid-bilayer bound extracellular vesicles of 40-160 nanometers in size that carry important information for intercellular communication. Exosomes are produced more by tumor cells than normal cells and carry tumor-specific content, such as DNA, RNA, and proteins, which have been implicated in tumorigenesis, tumor progression, and treatment response. Due to the critical role of exosomes in cancer development and progression, they can be exploited to develop specific biomarkers and therapeutic targets. Since exosomes are present in various biofluids, such as blood, saliva, urine, and peritoneal fluid, they are ideally suited to be developed as liquid biopsy tools for early diagnosis, molecular profiling, disease surveillance, and treatment response monitoring. In the past decade, numerous studies have been published about the functional significance of exosomes in a wide variety of cancers, with a particular focus on exosome-derived RNAs and proteins as biomarkers. In this review, utilizing human studies on exosomes, we highlight their potential as diagnostic, prognostic, and predictive biomarkers in gastrointestinal cancers.