Circulating tumor cells (CTCs) detected by RT-PCR and its prognostic role in gastric cancer: a meta-analysis of published literature

Investigating the role of circulating tumor cells in gastric cancer: a comprehensive systematic review and meta-analysis

Investigating the role of circulating tumor cells (CTCs) and their characteristics is still controversial in patients with gastric cancer (GC). Therefore, in this study, to provide a comprehensive review and meta-analyses of the literature on association of CTCs with gastric cancer, Scopus, Web of Science, Embase, and Medline were searched for systematic reviews and meta-analyses conducted during February 2022 using the keywords. Risk of bias, hazard ratios (HRs), and risk differences (RD) were assessed. Forty-five studies containing 3,342 GC patients from nine countries were assessed. The overall prevalence of CTC in GC was 69.37% (60.27, 77.78). The pooled result showed that increased mortality in GC patients was significantly associated with positive CTCs, poor overall survival (HR = 2.73, 95%CI 2.34-3.24, p < 0.001), and progression-free survival rate (HR = 2.78, 95%CI 2.01-3.85, p < 0.001). Subgroup analyses regarding markers, detection methods, treatment type, presence of distance metastasis, presence of lymph node metastasis, and overall risk of bias showed significant associations between the groups in terms of the incidence rates of CTCs, OS, and PFS. In addition, the results of risk differences based on sampling time showed that the use of the cell search method (RD: - 0.19, 95%CI (- 0.28, - 0.10), p < 0.001), epithelial marker (RD: - 0.12, 95%CI (- 0.25, 0.00), p 0.05) and mesenchymal markers (RD: - 0.35, 95%CI (- 0.57, - 0.13), p 0.002) before the treatment might have a higher diagnostic power to identify CTCs and also chemotherapy treatment (RD: - 0.17, 95%CI (- 0.31, - 0.03), p 0.016) could significantly reduce the number of CTCs after the treatment. We also found that the risk differences between the clinical early and advanced stages were not statistically significant (RD: - 0.10, 95%CI (- 0.23, 0.02), P 0.105). Also, in the Lauren classification, the incidence of CTC in the diffuse type (RD: - 0.19, 95%CI (- 0.37, - 0.01), P0.045) was higher than that in the intestinal type. Meta-regression analysis showed that baseline characteristics were not associated with the detection of CTCs in GC patients. According to our systematic review and meta-analysis, CTCs identification may be suggested as a diagnostic technique for gastric cancer screening, and the outcomes of CTC detection may also be utilized in the future to create personalized medicine programs.

Circulating tumor cells in gastric cancer: developments and clinical applications

Circulating tumor cells (CTCs), which are shed from primary tumor or metastatic sites into the bloodstream and subsequently seed into distant tissues, are considered as the precursors of metastases. Gastric cancer (GC) is a highly heterogeneous malignant tumor. With regard to the diagnosis of GC, secondary pathological biopsy is difficult, while invasive examination is harmful to patients. In recent years, CTCs have made great progress in tumor diagnosis, prognosis prediction, efficacy detection and treatment guidance, but the research on the role of CTCs in GC remains limited. The following sections review the landmark studies demonstrating the technical approaches of CTCs monitoring in the field of GC. Moreover, we highlight the clinical application of CTCs numbers and phenotypes in monitoring the therapeutic efficacy and judging patient prognosis by sequential blood analyses.

Biomarkers of gastric cancer: current advancement

Gastric cancer (GC) is one of the most prevalent malignant types worldwide, especially in East Asia. Due to its frequently advanced stage at diagnosis, the mortality from GC is high and the prognosis is still unsatisfactory. Thus, early detection using effective screening approaches is vital to decrease the morbidity and mortality of GC. Interestingly, biomarkers can be used for diagnosis, prediction of sensitivity to treatment, and prognosis in GC. The potential biomarkers detectable in liquid biopsies such as circulating tumor cells (CTCs), long non-coding RNAs (lncRNAs), cell-free DNA (cfDNA), microRNAs, and exosomes reveal numerous information regarding the early prediction and the outcomes for GC patients. Additionally, using the novel serum biomarkers has opened up new opportunities for diagnosing and monitoring patients with GC. This review mainly summarizes the novel progress and approaches in GC biomarkers, which could be potentially used for early diagnosis and therapy monitoring. Meanwhile, we also discussed the advantages, disadvantages, and future perspectives of GC biomarkers.

Bioplatforms in liquid biopsy: advances in the techniques for isolation, characterization and clinical applications

Tissue biopsy analysis has conventionally been the gold standard for cancer prognosis, diagnosis and prediction of responses/resistances to treatments. The existing biopsy procedures used in clinical practice are, however, invasive, painful and often associated with pitfalls like poor recovery of tumor cells and infeasibility for repetition in single patients. To circumvent these limitations, alternative non-invasive, rapid and economical, yet sturdy, consistent and dependable, biopsy techniques are required. Liquid biopsy is an emerging technology that fulfills these criteria and potentially much more in terms of subject-specific real-time monitoring of cancer progression, determination of tumor heterogeneity and treatment responses, and specific identification of the type and stages of cancers. The present review first briefly revisits the state-of-the-art technique of liquid biopsy and then proceeds to address in detail, the advances in the potential clinical applications of four major biological agencies present in liquid biopsy samples (circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), exosomes and tumor-educated platelets (TEPs)). Finally, the authors conclude with the limitations that need to be addressed in order for liquid biopsy to effectively replace the conventional invasive biopsy methods in the clinical settings.

Current status and future perspectives in HER2 positive advanced gastric cancer

Gastric cancer is one of the most common malignancy worldwide with a prognosis less than 1 year in unresectable or metastatic disease. HER2 expression is the main biomarker to lead the addition of trastuzumab to first line systemic chemotherapy improving the overall survival in advanced HER2-positivegastric adenocarcinoma. The inevitable development of resistance to trastuzumab remains a great problem inasmuch several treatment strategies that have proven effective in breast cancer failed to show clinical benefit in advanced gastric cancer. In this review, we summarize the available data on the mechanisms underlying primary and secondary resistance toHER2-targeted therapy and current challenges in the treatment of HER2-positive advanced gastric cancer refractory to trastuzumab. Further, we describe the prognostic value of new non-invasive screening techniques, the current development of novel agents such us HER2 antibody-drug conjugates and bispecific antibodies, and the strategies with antitumor activity on going.

Discriminating Epithelial to Mesenchymal Transition Phenotypes in Circulating Tumor Cells Isolated from Advanced Gastrointestinal Cancer Patients

Gastrointestinal (GI) cancers constitute a group of highest morbidity worldwide, with colorectal cancer (CRC) and gastric cancer being among the most frequently diagnosed. The majority of gastrointestinal cancer patients already present metastasis by the time of diagnosis, which is widely associated with cancer-related death. Accumulating evidence suggests that epithelial-to-mesenchymal transition (EMT) in cancer promotes circulating tumor cell (CTCs) formation, which ultimately drives metastasis development. These cells have emerged as a fundamental tool for cancer diagnosis and monitoring, as they reflect tumor heterogeneity and the clonal evolution of cancer in real-time. In particular, EMT phenotypes are commonly associated with therapy resistance. Thus, capturing these CTCs is expected to reveal important clinical information. However, currently available CTC isolation approaches are suboptimal and are often targeted to capture epithelial CTCs, leading to the loss of EMT or mesenchymal CTCs. Here, we describe size-based CTCs isolation using the RUBYchip™, a label-free microfluidic device, aiming to detect EMT biomarkers in CTCs from whole blood samples of GI cancer patients. We found that, for most cases, the mesenchymal phenotype was predominant, and in fact a considerable fraction of isolated CTCs did not express epithelial markers. The RUBYchip™ can overcome the limitations of label-dependent technologies and improve the identification of CTC subpopulations that may be related to different clinical outcomes.

Detection of Marker Associated with CTC in Colorectal Cancer in Mononuclear Cells of Patients with Benign Inflammatory Intestinal Diseases

Simple Summary

Colorectal carcinoma (CRC) is one of the most frequent cancers in western countries, and non-invasive methods for early detection are still needed. Circulating tumor cells (CTC) in blood of CRC patients have been proven as prognostic and predictive biomarker; however, the suitability of CTC-associated markers for early CRC detection and discrimination from benign diseases has not been analyzed. Thus, this study investigated whether CTC-associated markers can also be detected in the blood of patients with benign inflammatory intestinal disease (IID) or whether they are specific for malignancy. The detection rate of CK20 and DEFA5 clearly differed in diseased patients and healthy controls, while LAD1 and PLS3 was found in all samples but with clear qualitative differences in gene expression. No association between inflammation severity and CTC marker expression was found in IID patients. Finally, PLS3 was identified to be a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls.

Abstract

Colorectal carcinoma (CRC) belongs to the most common tumor entities in western countries. Circulating tumor cells (CTC) in blood of CRC patients are a powerful prognostic and predictive biomarker. However, whether CTC-associated markers can also be used for early CRC detection and discrimination from benign diseases is not known. This study investigated the presence of CTC-associated markers CK20, PLS3, LAD1, and DEFA5 in blood of patients with benign inflammatory intestinal disease (IID) and their correlation with malignancy. The detection rate of CK20 and DEFA5 significantly differed between diseased patients and healthy controls. LAD1 and PLS3 were detected in all samples with clear differences in gene expression. DEFA5 expression was higher in CRC and IID patients compared to healthy donors, while CK20 and PLS3 were lower in CRC compared to IID patients or healthy controls. Overall, all CTC-associated markers were detectable in blood of IID patients, but not correlating with inflammation severity. Finally, PLS3 emerged as a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls, however its suitability for early CRC detection needs to be further validated.

Clinical Applications of Liquid Biopsy in Gastric Cancer

Liquid biopsy represents an exciting new area in the field of cancer diagnosis and management, offering a less invasive and more convenient approach to obtain a time-point image of the tumor burden and its genomic profile. Samples collected from several body fluids, mostly blood, can be used to gain access to circulating tumor cells and DNA, non-coding RNAs, microRNAs, and exosomes, at any moment, offering a dynamic picture of the tumor. For patients with GC, the use of blood-based biopsies may be particularly beneficial since tissue biopsies are difficult to obtain and cause real distress to the patient. With advantages such as repeatability and minimal invasion, it is no wonder that the field of liquid biopsy has received tremendous attention. However, the abundance of studies, involving a wide range of assays with different principles, prevented for the moment the reproducibility of the results and therefore the translation into the clinic of liquid biopsy. In this review, we present the latest technical development and data on circulating biomarkers available through liquid biopsy in gastric cancer with an emphasis on their clinical utility in areas such as cancer screening, prognostic stratification, and therapeutic management.

Application of Primary/Secondary Circulating Tumor Cells for the Prediction of Biochemical Recurrence in Nonmetastatic Prostate Cancer Patients following Radical Prostatectomy or Radiotherapy: A Meta-Analysis

Background

Circulating tumor cells (CTCs) have been regarded as an independent prognostic marker for metastatic castration-resistant prostate cancer (mCRPC). Its prognostic value, however, in nonmetastatic prostate cancer (NMPC) is still unclear.

Purpose

To elucidate whether CTCs can predict the biochemical recurrence (BCR) in NMPC patients following radical prostatectomy (RP) or radiotherapy (RT).

Methods

PubMed, Cochrane Database, and Embase and the references in relevant studies were systematically searched. Studies that investigated the correlation of CTCs and BCR in NMPC patients after RP or RT were identified and reviewed. Overall odds ratio (OR) of BCR in such patients with/without CTCs was pooled. We also calculated and pooled overall prevalence of BCR in such CTC-positive patients.

Results

In total, 12 studies comprising 1917 participants were eligible for the meta-analysis and showed that the presence of secondary circulating tumor cells (SCTCs) is associated with a higher BCR rate of 59% (95% CI: 22%-88%) in patients with NMPC after RP or RT (OR = 6.12; 95% CI: 2.22-16.85; P < 0.001). However, regardless of the presence of primary circulating tumor cells (PCTCs), it has not been shown to be associated with higher BCR.

Conclusions

Our research demonstrated that SCTC-positive patients are associated with higher BCR compared to SCTC-negative patients in NMPC. Therefore, it is recommended that NMPC patients undergo CTC surveillance intensively after RP or RT.

Human epidermal growth factor receptor 2 (HER2) in advanced gastric cancer: where do we stand?

Gastric cancer is one of the most common malignancy worldwide. In unresectable or metastatic disease, the prognosis is poor and in generally less than a year. HER2 expression remains an important biomarker to lead the addition of trastuzumab to first-line systemic chemotherapy in unresectable or metastatic gastroesophageal adenocarcinoma. To date, a major issue is represented by resistance to trastuzumab developed during treatment, considering the not improved outcomes in this molecular subtype of gastroesophageal adenocarcinoma to other HER2 target strategies. In this review, we summarize the available data on the mechanisms underlying primary and secondary resistance to HER2-targeted therapy and current challenges in the treatment of HER2-positive advanced gastric cancer refractory to trastuzumab. Furthermore, we describe the prognostic value of new non-invasive screening methods, under development novel agents (e.g., HER2 antibody-drug conjugates and bispecific antibodies) and strategies with antitumor activity in early studies.

Biomarkers for Precision Urothelial Carcinoma Diagnosis: Current Approaches and the Application of Single-Cell Technologies

Simple Summary

Urothelial carcinoma (UC) is the most frequently diagnosed cancer of the urinary tract and is ranked the sixth most diagnosed cancer in men worldwide. About 70–75% of newly diagnosed UCs are non-invasive or low grade. Different tests such as urine cytology and cystoscopy are used to detect UC. If abnormal tissue is found during cystoscopy, then a biopsy will be performed. Cytology has low sensitivity for low-grade cancer while cystoscopy is invasive and costly. Detecting UC early improves the chances of treatment success. Therefore, many researchers have painstakingly identified urine biological markers for non-invasive UC diagnosis. In this review, we summarize some of the latest and most promising biological markers (including FDA-approved and investigational markers). We also discuss some new technologies that can aid research efforts in biological marker discovery for early UC detection.

Abstract

Urothelial carcinoma (UC) is the most frequent malignancy of the urinary system and is ranked the sixth most diagnosed cancer in men worldwide. Around 70–75% of newly diagnosed UC manifests as the non-muscle invasive bladder cancer (NMIBC) subtype, which can be treated by a transurethral resection of the tumor. However, patients require life-long monitoring due to its high rate of recurrence. The current gold standard for UC diagnosis, prognosis, and disease surveillance relies on a combination of cytology and cystoscopy, which is invasive, costly, and associated with comorbidities. Hence, there is considerable interest in the development of highly specific and sensitive urinary biomarkers for the non-invasive early detection of UC. In this review, we assess the performance of current diagnostic assays for UC and highlight some of the most promising biomarkers investigated to date. We also highlight some of the recent advances in single-cell technologies that may offer a paradigm shift in the field of UC biomarker discovery and precision diagnostics.

Human Epidermal Growth Factor Receptor 2 (HER2) in Advanced Gastric Cancer: Current Knowledge and Future Perspectives

The discovery of human epidermal growth factor receptor 2 (HER2) overexpression in 15-20% of gastric adenocarcinomas has been a key advance in the global care of this disease. Validated by the ToGA trial in the first-line setting of advanced HER2-positive (+) gastric cancer (GC), trastuzumab, an anti-HER2 monoclonal antibody (mAb), was the first therapeutic agent to significantly improve the prognosis of these patients. Since these results, many attempts have been made to improve the clinical outcomes of patients with HER2+ GC. However, all the other HER2-targeting molecules have failed to show a survival benefit in large phase III studies. The value of continuing trastuzumab after disease progression has been suggested by several retrospective studies. However, recent results of a randomized phase II trial showed no benefit from this strategy. On the other hand, novel therapeutic methods, such as immunotherapy, are emerging as new tools in the strategy of care of advanced GC, even if their benefit in the specific HER2+ population remains undetermined. Furthermore, substantial progress has been made in the understanding of the mechanisms leading to resistance to anti-HER2 therapies, and in the screening methods to detect them, thus opening new perspectives. The aim of this review was firstly to summarize the existing data on the specific strategy of care of HER2+ advanced GC, and secondly, to describe current knowledge regarding the potential mechanisms of resistance to HER2-targeting therapies. Lastly, we report the prospects for overcoming these potential obstacles, from future therapeutic strategies to new detection methods.

Tumor circulome in the liquid biopsies for digestive tract cancer diagnosis and prognosis

Digestive tract cancer is one of the main diseases that endanger human health. At present, the early diagnosis of digestive tract tumors mainly depends on serology, imaging, endoscopy, and so on. Although tissue specimens are the gold standard for cancer diagnosis, with the rapid development of precision medicine in cancer, the demand for dynamic monitoring of tumor molecular characteristics has increased. Liquid biopsy involves the collection of body fluids via non-invasive approaches, and analyzes biological markers such as circulating tumor cells, circulating tumor DNA, circulating cell-free DNA, microRNAs, and exosomes. In recent years, liquid biopsy has become more and more important in the diagnosis and prognosis of cancer in clinical practice due to its convenience, non-invasiveness, high specificity and it overcomes temporal-spatial heterogeneity. Therefore, this review summarizes the current evidence on liquid biopsies in digestive tract cancers in relation to diagnosis and prognosis.

Circulating Tumor Cells in Gastrointestinal Cancers: Current Status and Future Perspectives

Circulating tumor cells (CTCs), which are now defined as the "break away" cancer cells that derive from primary- or metastatic-tumor sites and present in the bloodstream, are considered to be the precursors of metastases. Considering the key role of CTCs in cancer progression, researchers are committed to analyze them in the past decades and many technologies have been proposed for achieving CTCs isolation and characterization with highly sensitivity and specificity until now. On this basis, clinicians gradually realize the clinical values of CTCs' detection through various clinical studies. As a "liquid biopsy," CTCs' detection and measurement can supply important information for predicting patient's survival, monitoring of response/resistance, assessment of minimal residual disease, evaluating distant metastasis, and sometimes, customizing therapy choices. Nowadays, eliminating CTCs of the blood circulation has been regarded as a promising method to prevent tumor metastasis. However, research on CTCs still faces many challenges. Herein, we present an overview to discuss the current concept of CTCs, summarize the available techniques for CTCs detection, and provide an update on the clinical significance of CTCs in gastrointestinal malignancies, especially focus on gastric and colorectal cancer.

Prognostic and therapeutic significance of circulating tumor cells in patients with lung cancer

BACKGROUND

Lung cancer is the second most common cancer and the main cause of cancer-related mortality worldwide. In spite of various efforts that have been made to facilitate the early diagnosis of lung cancer, most patients are diagnosed when the disease is already in stage IV, which is generally associated with the occurrence of distant metastases and a poor survival. Moreover, a large proportion of these patients will relapse after treatment, heralding the need for the stratification of lung cancer patients in addition to identifying those who are at a higher risk of relapse and, thus, require alternative and/or additional therapies. Recently, circulating tumor cells (CTCs) have been considered as valuable markers for the early diagnosis, prognosis and risk stratification of cancer patients, and they have been found to be able to predict the survival of patients with various types of cancer, including lung cancer. Additionally, the characterization of CTCs has recently provided fascinating insights into the heterogeneity of tumors, which may be instrumental for the development of novel targeted therapies.

CONCLUSIONS

Here we review our current understanding of the significance of CTCs in lung cancer metastasis. We also discuss prominent studies reporting the utility of enumeration and characterization of CTCs in lung cancer patients as prognostic and pharmacodynamic biomarkers for those who are at a higher risk of metastasis and drug resistance.

Prognostic Biomarkers for Gastric Cancer: An Umbrella Review of the Evidence

Introduction: Biomarkers are biological molecules entirely or partially participating in cancerous processes that function as measurable indicators of abnormal changes in the human body microenvironment. Aiming to provide an overview of associations between prognostic biomarkers and gastric cancer (GC), we performed this umbrella review analyzing currently available meta-analyses and grading the evidence depending on the credibility of their associations. Methods: A systematic literature search was conducted by two independent investigators of the PubMed, Embase, Web of Science, and Cochrane Databases to identify meta-analyses investigating associations between prognostic biomarkers and GC. The strength of evidence for prognostic biomarkers for GC were categorized into four grades: strong, highly suggestive, suggestive, and weak. Results: Among 120 associations between prognostic biomarkers and GC survival outcomes, only one association, namely the association between platelet count and GC OS, was supported by strong evidence. Associations between FITC, CEA, NLR, foxp3+ Treg lymphocytes (both 1- and 3-year OS), CA 19-9, or VEGF and GC OS were supported by highly suggestive evidence. Four associations were considered suggestive and the remaining 108 associations were supported by weak or not suggestive evidence. Discussion: The association between platelet count and GC OS was supported by strong evidence. Associations between FITC, CEA, NLR, foxp3+ Treg lymphocytes (both 1- and 3-year OS), CA 19-9, or VEGF and GC OS were supported by highly suggestive evidence, however, the results should be interpreted cautiously due to inadequate methodological quality as deemed by AMSTAR 2.0.

Liquid Biopsy in Gastrointestinal Cancers

Liquid biopsy is the sampling of any biological fluid in an effort to enrich and analyze a tumor's genetic material. Peripheral blood remains the most studied liquid biopsy material, with circulating tumor cells (CTC's) and circulating tumor DNA (ctDNA) allowing the examination and longitudinal monitoring of a tumors genetic landscape. With applications in cancer screening, prognostic stratification, therapy selection and disease surveillance, liquid biopsy represents an exciting new paradigm in the field of cancer diagnostics and offers a less invasive and more comprehensive alternative to conventional tissue biopsy. Here, we examine liquid biopsies in gastrointestinal cancers, specifically colorectal, gastric, and pancreatic cancers, with an emphasis on applications in diagnostics, prognostics and therapeutics.

Liquid Biopsy Biomarkers in Bladder Cancer: A Current Need for Patient Diagnosis and Monitoring

Bladder Cancer (BC) represents a clinical and social challenge due to its high incidence and recurrence rates, as well as the limited advances in effective disease management. Currently, a combination of cytology and cystoscopy is the routinely used methodology for diagnosis, prognosis and disease surveillance. However, both the poor sensitivity of cytology tests as well as the high invasiveness and big variation in tumour stage and grade interpretation using cystoscopy, emphasizes the urgent need for improvements in BC clinical guidance. Liquid biopsy represents a new non-invasive approach that has been extensively studied over the last decade and holds great promise. Even though its clinical use is still compromised, multiple studies have recently focused on the potential application of biomarkers in liquid biopsies for BC, including circulating tumour cells and DNA, RNAs, proteins and peptides, metabolites and extracellular vesicles. In this review, we summarize the present knowledge on the different types of biomarkers, their potential use in liquid biopsy and clinical applications in BC.

Liquid Biopsy in Head and Neck Cancer: Promises and Challenges

Head and neck cancer is the sixth most common cancer worldwide. It remains one of the leading causes of death, and its early detection is crucial. Liquid biopsy has emerged as a promising tool for detecting and monitoring the disease status of patients with early and advanced cancers. Circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and exosomal miRNAs have received enormous attention because of their apparent clinical implications. Analyses of these circulating biomarkers have paved the way for novel therapeutic approaches and precision medicine. A growing number of reports have implicated the use of circulating biomarkers for detection, treatment planning, response monitoring, and prognosis assessment. Although these new biomarkers can provide a wide range of possible clinical applications, no validated circulating biomarkers have yet been integrated into clinical practice for head and neck cancer. In this review, we summarize the current knowledge of circulating biomarkers in this field, focusing on their feasibility, limitations, and key areas of clinical applications. We also highlight recent advances in salivary diagnostics and their potential application in head and neck cancer.

Prognostic value of circulating tumor cells detected with the CellSearch System in patients with gastric cancer: evidence from a meta-analysis

Background

Circulating tumor cells (CTCs) have been proposed as a marker for predicting the prognosis of cancer. However, the prognostic value of CTCs detected with the CellSearch System in patients with gastric cancer (GC) remains controversial. We performed a meta-analysis of available studies to investigate this topic.

Methods

Two authors systematically searched the studies independently in PubMed, Science Citation Index, Cochrane Database, Embase, and the references in relevant studies (up to September 2017) using keywords. Our meta-analysis was performed in Stata software, version 12.0 (2011; Stata Corp, College Station, TX, USA), with the risk ratio (RR), hazard ratio (HR), and 95% CI as the effect measures. Subgroup analyses and meta-regression were also conducted.

Results

Seven studies (including eight sets of data) containing 579 patients with GC from four countries were included in this meta-analysis. The pooled results showed CTC-positive status detected by the CellSearch System was significantly associated with poor overall survival (HR =2.09, 95% CI [1.71, 2.55], P<0.001, I²=31.5%) and progression-free survival (HR =2.11, 95% CI [1.25, 3.57], P=0.005, I²=75.6%) of patients with GC, regardless of sampling time. The disease control rate of CTC-positive group was lower than that of CTC-negative group for both baseline and intra-therapy, although no statistical difference existed at both sampling time points (baseline: 69.5% versus 81.8%, RR=0.79, 95% CI [0.54, 1.16], P=0.23, I²=68.0%; intra-therapy: 50.0% versus 85.9%, RR=0.24, 95% CI [0.02, 3.13], P=0.28, I²=87.4%).

Conclusion

Our meta-analysis demonstrated that CTCs detected with the CellSearch System from the peripheral blood had significant prognostic value and might predict poor response to chemotherapy for patients with GC.

Circulating tumour cells and DNA as liquid biopsies in gastrointestinal cancer

Background

Blood is the most extensively studied body fluid and, because it contains circulating tumour cells (CTCs) and circulating tumour-derived cell-free DNA (ctDNA), it may represent a liquid biopsy for cancer. Methods for enrichment and detection of CTCs and ctDNA, their clinical applications and future opportunities in gastrointestinal cancers were the focus of this review.

Methods

The PubMed database was searched for literature up to 24 June 2017, with a focus on the past 10 years. Identified articles were further scrutinized for relevant references. Articles were those in English relating to colorectal, gastric and pancreatic cancer.

Results

Both CTCs and ctDNA are in low abundance compared with other cellular components of blood, but effective enrichment and highly sensitive techniques are available for their detection. Potential clinical applications of these liquid biopsies include screening, prognostic stratification, therapy administration, monitoring of treatment effect or resistance, and surveillance. Liquid biopsies provide opportunities to reduce the need for invasive tissue sampling, especially in the context of intratumoral heterogeneity and the need for tumour genotyping.

Conclusion

Liquid biopsies have applications in gastrointestinal cancers to improve clinical decision-making.

Systemic immune-inflammation index, thymidine phosphorylase and survival of localized gastric cancer patients after curative resection

Systemic immune-inflammation index (SII), based on lymphocyte (L), neutrophil (N), and platelet (P) counts, was recently developed and reflects comprehensively the balance of host inflammatory and immune status. We explored its prognostic value in localized gastric cancer (GC) after R0 resection and the potential associations with Thymidine phosphorylase (TYMP), which was reported to increase the migration and invasion of gastric cancer cells. A total of 455 GC patients who received D2 gastrectomy were enrolled. Blood samples were obtained within 1 week before surgery to measure SII (SII = P × N/L). TYMP expression was measured on tumor sections by immunohistochemical analysis. Preoperative high SII indicated worse prognosis (HR: 1.799; 95% CI: 1.174-2.757; p = 0.007) in multivariate analysis and was associated with higher pathological TNM stage, deeper local invasion of tumor and lymph node metastasis (all p < 0.001). SII predicted poor overall survival in pathological TNM stage I subgroup also (p < 0.001). Furthermore we found that in high SII group, positive rate of TYMP expression increased (53.7% vs 42.7%, p = 0.046) and TYMP positive patients had higher SII score (median 405.9 vs. 351.9, p = 0.026). SII, as a noninvasive and low cost prognostic marker, may be helpful to identify higher-risk patients after R0 resection, even for stage I GC patients.

The prognostic and diagnostic value of circulating tumor cells in bladder cancer and upper tract urothelial carcinoma: a meta-analysis of 30 published studies

There are inconsistent conclusions in the association between circulating tumor cells (CTCs) and urothelial cancer (UC). We performed a meta-analysis to assess the prognostic and diagnostic value of CTCs in UC. We search Medline, Embase and Web of science for relevant studies. The study was set up according to the inclusion/exclusion criteria. 30 published studies with a total of 2161 urothelial cancer patients were included. Meta-analysis showed that CTC-positive was significantly associated with tumor stage (≤ II vs III, IV) (OR = 4.60, 95% CI: 2.34-9.03), histological grade (I, II vs III) (OR = 2.91, 95% CI: 1.92-4.40), metastasis (OR = 5.12, 95% CI: 3.47-7.55) and regional lymph node metastasis (OR = 2.47, 95% CI: 1.75-3.49). It was also significantly associated with poor overall survival (OS) (HR = 3.98, 95% CI: 2.20-7.21), progression/disease-free survival (PFS/DFS) (HR = 2.22, 95% CI: 1.80-2.73) and cancer-specific survival (CSS) (HR = 5.18, 95% CI: 2.21-12.13). Overall sensitivity and specificity of CTC detection assays were 0.35 (95% CI: 0.28-0.43) and 0.97 (95% CI: 0.92-0.99) respectively. In summary, our meta-analysis suggests that the presence of CTCs in the peripheral blood is an independent predictive indicator of poor outcomes for urothelial cancer patients. It can also be used as a noninvasive method for the confirmation of cancer diagnosis. More studies are required to further explore the role of this marker in clinical practice.

Melanoma antigen-encoding gene family member A1-6 and hTERT in the detection of circulating tumor cells following CD45- depletion and RNA extraction

A total of 76 blood samples from patients without malignant disease and 107 blood samples from patients with malignant disease were investigated for the presence of circulating tumor cells (CTCs). To detect CTCs, hematopoietic cells were removed from the blood samples and different RNA extraction methods were used to amplify the melanoma antigen-encoding gene family member A1-family member A6 (MAGE A1-6) and the human telomerase reverse transcriptase (hTERT) gene as potential CTC markers. Comparison between four methods for extracting RNA from the blood was performed. The samples were enriched by cluster of differentiation 45 (CD45) antibody capturing, and the reverse transcription-quantitative polymerase chain reaction was used to amplify the MAGE A1-6 and hTERT genes. MAGE A1-6 and hTERT gene expression levels were also evaluated in 14 cancer cell lines, and the MAGE A1-6 and hTERT expression levels were 85.7 and 100%, respectively. The RNeasy method demonstrated the most sensitivity in the SNU1 cells mixed with blood, although the differences between methods was non-significant. The positive expression levels of MAGE A1-6 and hTERT was 11.8% in the control group and 58.9% in those with malignant disease. In the 70 patients with colorectal cancer, positive expression levels of MAGE A1-6 or hTERT were significantly higher in stages T3 and T4 compared with in stages T1 and T2. The CTC detection method involving CD45 antibody capture, RNA extraction and MAGE A1-6 and hTERT reverse transcription resulted in good rates of sensitivity and specificity. Thus, the present study concluded that MAGE A1-6 and hTERT genes may be potential and practical markers for CTCs in a clinical setting.

Clinical significance of circulating tumor cells in blood from patients with gastric cancer

Circulating tumor cells (CTC) have been focused on as a target for detecting occult tumors, predicting therapeutic responses and prognoses, and monitoring postoperative recurrence in the clinical management of patients with various malignancies, including gastric cancer. Recent advances in molecular diagnostic tools have contributed to high sensitivity and specificity for the detection of CTC. A conspicuous disparity exists in the incidence of CTC among studies. However, a close relationship has been reported between positivity for CTC and well‐known prognostic clinicopathological factors including depth of tumor invasion, lymph node metastasis, stage, and lymphatic and venous invasion in patients with gastric cancer. According to most studies published on the clinical impact of CTC, the presence of CTC negatively affects the prognosis of patients with gastric cancer. Moreover, the study of CTC based on a meta‐analysis demonstrated their importance as a poor prognostic indicator. In clinical management, pre‐ and post‐therapeutic monitoring of CTC using liquid biopsy may be useful for early detection of subclinical patients or disease recurrence, prediction of tumor progression, and administrative control of adjuvant chemotherapy. Although their functional properties remain unclear, molecular profiling of CTC may contribute to the development of personalized treatment that effectively inhibits tumor progression in patients with advanced gastric cancer. We herein review the clinical significance of CTC as a promising blood marker and therapeutic target in patients with gastric cancer.

Liquid Biopsy for Cancer: Circulating Tumor Cells, Circulating Free DNA or Exosomes?

Precision medicine and personalized medicine are based on the development of biomarkers, and liquid biopsy has been reported to be able to detect biomarkers that carry information on tumor development and progression. Compared with traditional 'solid biopsy', which cannot always be performed to determine tumor dynamics, liquid biopsy has notable advantages in that it is a noninvasive modality that can provide diagnostic and prognostic information prior to treatment, during treatment and during progression. In this review, we describe the source, characteristics, technology for detection and current situation of circulating tumor cells, circulating free DNA and exosomes used for diagnosis, recurrence monitoring, prognosis assessment and medication planning.

Circulating tumor cells and circulating tumor DNA: What surgical oncologists need to know?

As a result of recent progress in detection techniques, circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) can now be accurately detected in the blood of most cancer patients. While these new biomarkers can provide a better understanding of key biological mechanisms underlying cancer growth and dissemination, they also open up a wide range of possible clinical applications in medical oncology, radiation oncology and surgical oncology. In this review, we summarize the results obtained with ctDNA and CTC together with their potential future clinical applications in the field of surgical oncology, with particular focus on the perioperative setting of various types of cancer. These applications include, but are not limited to, cancer screening, early diagnosis, prognostic assessment, evaluation and management of preoperative systemic or local therapies, post-surgical detection of minimal residual disease and early detection of cancer relapse.

Aptamer-Mediated Transparent-Biocompatible Nanostructured Surfaces for Hepotocellular Circulating Tumor Cells Enrichment

Circulating tumor cells (CTCs) have been considered as the origin of cancer metastasis. Thus, detection of CTCs in peripheral blood is of great value in different types of solid tumors. However, owing to extremely low abundance of CTCs, detection of them has been technically challenging. To establish a simple and efficient method for CTCs detection in patients with hepatocellular carcinoma (HCC), we applied biocompatible and transparent HA/CTS (Hydroxyapatite/chitosan) nanofilm to achieve enhanced topographic interactions with nanoscale cellular surface components, and we used sLex-AP (aptamer for carbohydrate sialyl Lewis X) to coat onto HA/CTS nanofilm for efficient capture of HCC CTCs, these two functional components combined to form our CTC-^BioTChip platform. Using this platform, we realized HCC CTCs' capture and identification, the average recovery rate was 61.6% or more at each spiking level. Importantly, our platform identified CTCs (2±2 per 2 mL) in 25 of 42 (59.5%) HCC patients. Moreover, both the positivity rate and the number of detected CTCs were significantly correlated with tumor size, portal vein tumor thrombus, and the TNM (tumor-node-metastasis) stage. In summary, our CTC-^BioTChip platform provides a new method allowing for simple but efficient detection of CTCs in HCC patients, and it holds potential of clinically usefulness in monitoring HCC prognosis and guiding individualized treatment in the future.

Noninvasive detection of gastric cancer

Gastric cancer (GC) is the fifth most common cancer and the third common cause of cancer death worldwide. Endoscopy is the most effective method for GC screening, but its application is limited by the invasion. Therefore, continuous efforts have been made to develop noninvasive methods for GC detection and promising results have been reported. Here, we review the advances in GC detection by protein and nucleic acid tumor markers, circulating tumor cells, and tumor-associated autoantibodies in peripheral blood. Some potential new noninvasive methods for GC detection are also reviewed, including exhaled breath analysis, blood spectroscopy analysis and molecular imaging.

A novel splice variant of XIAP-associated factor 1 (XAF1) is expressed in peripheral blood containing gastric cancer-derived circulating tumor cells

BACKGROUND

XIAP-associated factor 1 (XAF1) is ubiquitously expressed in normal tissues, but its suppression in cancer cells is strongly associated with tumor progression. Although downregulation of XAF1 is observed in tumors, its expression profile in the peripheral blood of cancer patients has not yet been investigated. Here, we identified a novel XAF1 splice variant in cancer cells and then investigated the expression level of this variant in peripheral blood containing gastric cancer-derived circulating tumor cells (CTCs).

METHODS

To identify splice variants, RT-PCR and DNA sequencing were performed in mRNAs extracted from many cancer cells. We then carried out quantitative RT-PCR to investigate expression in peripheral blood from all 96 gastric cancer patients and 22 healthy volunteers.

RESULTS

The XAF1 variant harbored a premature termination codon (PTC) and was differentially expressed in highly metastatic cancer cells versus the parental cells, and that nonsense-mediated mRNA decay (NMD) was suppressed in the variant-expressing cells. Furthermore, splice variants of XAF1 were upregulated in peripheral blood containing CTCs. In XAF1 variant-expressing patients, the expression levels of other NMD-targeted genes also increased, suggesting that the NMD pathway was suppressed in CTCs.

CONCLUSIONS

Our study identified a novel splice variant of XAF1 in cancer cells. This variant was regulated through the NMD pathway and accumulated in NMD-suppressed metastatic cancer cells and peripheral blood containing CTCs. The presence of XAF1 transcripts harboring the PTC in the peripheral blood may be useful as an indicator of NMD inhibition in CTCs.

Prognostic Value of Circulating Tumor Cells in Ovarian Cancer: A Meta-Analysis

Background

The prognostic value of circulating tumor cells (CTCs) in ovarian cancer has been investigated in previous studies, but the results are controversial. Therefore we performed a meta-analysis to systematically review these data and evaluate the value of CTCs in ovarian cancer.

Materials and Methods

A literary search for relevant studies was performed on Embase, Medline and Web of Science databases. Then pooled hazard ratios (HRs) for survival with 95% confidence intervals (CIs), subgroup analyses, sensitivity analyses, meta-regression analyses and publication bias were conducted.

Results

This meta-analysis is based on 11 publications and comprises a total of 1129 patients. The prognostic value of the CTC status was significant in overall survival (OS) (HR, 1.61;95% CI,1.22–2.13) and progression-free survival (PFS)/disease-free survival (DFS) (HR, 1.44; 95%CI, 1.18–1.75). Furthermore, subgroup analysis revealed that the value of CTC status in OS was significant in "RT-PCR" subgroup (HR, 2.02; 95% CI, 1.34–3.03), whereas it was not significant in "CellSearch" subgroup (HR, 1.15; 95% CI 0.45–2.92) and "other ICC" subgroup (HR, 1.09; 95% CI 0.62–1.90). The presence of CTC was also associated with an increased CA-125 (OR, 4.07; 95%CI, 1.87–8.85).

Conclusion

Our study demonstrates that CTC status is associated with OS and PFS/DFS in ovarian cancer.

Meta-analysis shows that circulating tumor cells including circulating microRNAs are useful to predict the survival of patients with gastric cancer

Background

Circulating tumor cells (CTCs) are metastatic cells disseminated into the bloodstreams. They have been proposed to monitor disease progression for decades. However, the prognostic value of CTCs in gastric cancer (GC) remains controversial. We performed a meta-analysis to investigate the topic.

Methods

A systematic search was made for relevant studies in academic data bases, involving the Medline, Embase, and Science Citation Index. Data on prognosis of GC patients, such as recurrence-free survival (RFS) and overall survival (OS), were extracted when possible. The meta-analysis was performed with the random effects model and the pooled hazard ratios (HRs) and their associated 95% confident intervals (95%CIs) were computed as effect measures.

Results

Twenty six studies (including 40 subgroups) with peripheral blood samples of 1950 cases from 10 countries were included in the final analysis. The pooled results showed that GC patients with detectable CTCs (including circulating miRNAs) had a tendency to experience shortened RFS (HR = 2.91, 95% CI [1.84-4.61], I² = 52.18%, n = 10). As for patient deaths, we found a similar association of CTC (including circulating miRNAs) presence with worse OS (HR = 1.78, 95% CI [1.49-2.12], I² = 30.71%, n = 30). Additionally, subgroup analyses indicated strong prognostic powers of CTCs, irrespective of geographical, methodological, detection time and sample size differences of the studies.

Conclusions

Our meta-analysis shows that CTCs (including circulating miRNAs) can predict the survival of GC patients. Large prospective studies are warranted to determine the best sampling time points, detection methods in homogeneous patients with GC in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-773) contains supplementary material, which is available to authorized users.