Concordance of anaplastic lymphoma kinase (ALK) gene rearrangements between circulating tumor cells and tumor in non-small cell lung cancer

Liquid biopsy in lung cancer: The role of circulating tumor cells in diagnosis, treatment, and prognosis

Despite numerous therapeutic advancements, such as immune checkpoint inhibitors, lung cancer continues to be the leading cause of cancer-related mortality. Therefore, the identification of cancer at an early stage is becoming a significant subject in contemporary oncology. Despite significant advancements in early detection tactics in recent decades, they continue to provide challenges because of the inconspicuous symptoms observed during the early stages of the primary tumor. Presently, tumor biomarkers and imaging techniques are extensively employed across different forms of cancer. Nevertheless, every approach has its own set of constraints. In certain instances, the detriments outweigh the advantages. Hence, there is an urgent need to enhance early detection methods. Currently, liquid biopsy is considered more flexible and not intrusive method in comparison to conventional test for early detection. Circulating tumor cells (CTCs) are crucial components of liquid biopsy and have a pivotal function in the spread and formation of secondary tumors. These indicators show great promise in the early identification of cancer. This study presents a comprehensive examination of the methodologies employed for the isolation and enrichment of circulating tumor cells (CTCs) in lung cancer. Additionally, it explores the formation of clusters of CTCs, which have a pivotal function in facilitating the effective dissemination of cancer to distant organs. In addition, we discuss the importance of CTCs in the detection, treatment, and prognosis of lung cancer.

Liquid Biopsies in Lung Cancer

As lung cancer has the highest cancer-specific mortality rates worldwide, there is an urgent need for new therapeutic and diagnostic approaches to detect early-stage tumors and to monitor their response to the therapy. In addition to the well-established tissue biopsy analysis, liquid-biopsy-based assays may evolve as an important diagnostic tool. The analysis of circulating tumor DNA (ctDNA) is the most established method, followed by other methods such as the analysis of circulating tumor cells (CTCs), microRNAs (miRNAs), and extracellular vesicles (EVs). Both PCR- and NGS-based assays are used for the mutational assessment of lung cancer, including the most frequent driver mutations. However, ctDNA analysis might also play a role in monitoring the efficacy of immunotherapy and its recent accomplishments in the landscape of state-of-the-art lung cancer therapy. Despite the promising aspects of liquid-biopsy-based assays, there are some limitations regarding their sensitivity (risk of false-negative results) and specificity (interpretation of false-positive results). Hence, further studies are needed to evaluate the usefulness of liquid biopsies for lung cancer. Liquid-biopsy-based assays might be integrated into the diagnostic guidelines for lung cancer as a tool to complement conventional tissue sampling.

Liquid Biopsy Analysis as a Tool for TKI-Based Treatment in Non-Small Cell Lung Cancer

The treatment of non-small cell lung cancer (NSCLC) has recently evolved with the introduction of targeted therapy based on the use of tyrosine kinase inhibitors (TKIs) in patients with certain gene alterations, including EGFR, ALK, ROS1, BRAF, and MET genes. Molecular targeted therapy based on TKIs has improved clinical outcomes in a large number of NSCLC patients with advanced disease, enabling significantly longer progression-free survival (PFS). Liquid biopsy is an increasingly popular diagnostic tool for treating TKI-based NSCLC. The studies presented in this article show that detection and analysis based on liquid biopsy elements such as circulating tumor cells (CTCs), cell-free DNA (cfDNA), exosomes, and/or tumor-educated platelets (TEPs) can contribute to the appropriate selection and monitoring of targeted therapy in NSCLC patients as complementary to invasive tissue biopsy. The detection of these elements, combined with their molecular analysis (using, e.g., digital PCR (dPCR), next generation sequencing (NGS), shallow whole genome sequencing (sWGS)), enables the detection of mutations, which are required for the TKI treatment. Despite such promising results obtained by many research teams, it is still necessary to carry out prospective studies on a larger group of patients in order to validate these methods before their application in clinical practice.

Novel Markers for Liquid Biopsies in Cancer Management: Circulating Platelets and Extracellular Vesicles

Although radiologic imaging and histologic assessment of tumor tissues are classic approaches for diagnosis and monitoring of treatment response, they have many limitations. These include challenges in distinguishing benign from malignant masses, difficult access to the tumor, high cost of the procedures, and tumor heterogeneity. In this setting, liquid biopsy has emerged as a potential alternative for both diagnostic and monitoring purposes. The approaches to liquid biopsy include cell-free DNA/circulating tumor DNA, long and micro noncoding RNAs, proteins/peptides, carbohydrates/lectins, lipids, and metabolites. Other approaches include detection and analysis of circulating tumor cells, extracellular vesicles, and tumor-activated platelets. Ultimately, reliable use of liquid biopsies requires bioinformatics and statistical integration of multiple datasets to achieve approval in a Clinical Laboratory Improvement Amendments setting. This review provides a balanced and critical assessment of recent discoveries regarding tumor-derived biomarkers in liquid biopsies along with the potential and pitfalls for cancer detection and longitudinal monitoring.

A Retrospective Study of Effectiveness of Thoracoscopic Lobectomy and Segmentectomy in Patients with Early-Stage Non-Small-Cell Lung Cancer

Background

Surgical treatment is the first choice for non-small-cell lung cancer. To date, there are only few studies on the changes in laboratory indexes in two types of surgery, namely, thoracoscopic lobectomy and segmental pneumonectomy.

Aim

To investigate the clinical impact of thoracoscopic lobectomy and segmentectomy in patients with early-stage non-small-cell lung cancer.

Methods

We retrospectively reviewed the medical records of 94 patients with early-stage NSCLC in our hospital from October 2017 to October 2019. The patients were divided into two groups. The patients in control and observation groups received thoracoscopic lobectomy and thoracoscopic segmentectomy, respectively. The perioperative indicators, complications, lung function, T cell subsets, tumor markers, follow-up of tumor recurrence rate, and survival rate were compared between two groups.

Results

The operation time of the observation group was longer, and the chest drainage volume was less at 24-48 h after the operation, and the chest tube indwelling time and postoperative hospital stay were shorter than those of the control group. No significant differences in complication probability were observed between two groups. The levels of FEV1, FVC, and MVV in the two groups were lower than those before the operation at 3 days after surgery, but the FEV1, FVC, and MVV levels in the observation group were higher than those in the control group. The CD3+, CD4+, and CD4+/CD8+ levels in the two groups were lower than those before the operation at 24 h and 72 h after the operation, but CD3+, CD4+, and CD4+/CD8+ levels in the observation group were higher than those of the control group.

Conclusion

Thoracoscopic lobectomy and segmental resection have similar clinical effects in the treatment of early-stage NSCLC patients, but segmental resection can preserve healthy lung tissue as much as possible, with less trauma, protect lung function, and promote postoperative recovery.

Sensitizing drug-resistant cancer cells from blood using microfluidic electroporator

Direct assessment of patient samples holds unprecedented potential in the treatment of cancer. Circulating tumor cells (CTCs) in liquid biopsies are a rapidly evolving source of primary cells in the clinic and are ideal candidates for functional assays to uncover real-time tumor information in real-time. However, a lack of routines allowing direct and active interrogation of CTCs directly from liquid biopsy samples represents a bottleneck for the translational use of liquid biopsies in clinical settings. To address this, we present a workflow for using a microfluidic vortex-assisted electroporation system designed for the functional assessment of CTCs purified from blood. Validation of this approach was assessed through drug response assays on wild-type (HCC827 wt) and gefitinib-resistant (HCC827 GR6) non-small cell lung cancer (NSCLC) cells. HCC827 cells trapped within microscale vortices were electroporated to sequentially deliver drug agents into the cytosol. Electroporation conditions facilitating multi-agent delivery were characterized for both cell lines using an automatic single-cell image fluorescence intensity algorithm. HCC827 GR6 cells spiked into the blood to emulate drug-resistant CTCs were able to be collected with high purity, demonstrating the ability of the device to minimize background cell impact for downstream sensitive cell assays. Using our proposed workflow, drug agent combinations to restore gefitinib sensitivity reflected the anticipated cytotoxic response. Taken together, these results represent a microfluidics multi-drug screening panel workflow that can enable functional interrogation of patient CTCs in situ, thereby accelerating the clinical standardization of liquid biopsies.

Molecular diagnosis in non-small-cell lung cancer: expert opinion on ALK and ROS1 testing

The effectiveness of targeted therapies with tyrosine kinase inhibitors in non-small-cell lung cancer (NSCLC) depends on the accurate determination of the genomic status of the tumour. For this reason, molecular analyses to detect genetic rearrangements in some genes (ie, ALK, ROS1, RET and NTRK) have become standard in patients with advanced disease. Since immunohistochemistry is easier to implement and interpret, it is normally used as the screening procedure, while fluorescence in situ hybridisation (FISH) is used to confirm the rearrangement and decide on ambiguous immunostainings. Although FISH is considered the most sensitive method for the detection of ALK and ROS1 rearrangements, the interpretation of results requires detailed guidelines. In this review, we discuss the various technologies available to evaluate ALK and ROS1 genomic rearrangements using these techniques. Other techniques such as real-time PCR and next-generation sequencing have been developed recently to evaluate ALK and ROS1 gene rearrangements, but some limitations prevent their full implementation in the clinical setting. Similarly, liquid biopsies have the potential to change the treatment of patients with advanced lung cancer, but further research is required before this technology can be applied in routine clinical practice. We discuss the technical requirements of laboratories in the light of quality assurance programmes. Finally, we review the recent updates made to the guidelines for the determination of molecular biomarkers in patients with NSCLC.

Molecular Pathology of Lung Cancer

This overview of the molecular pathology of lung cancer includes a review of the most salient molecular alterations of the genome, transcriptome, and the epigenome. The insights provided by the growing use of next-generation sequencing (NGS) in lung cancer will be discussed, and interrelated concepts such as intertumor heterogeneity, intratumor heterogeneity, tumor mutational burden, and the advent of liquid biopsy will be explored. Moreover, this work describes how the evolving field of molecular pathology refines the understanding of different histologic phenotypes of non-small-cell lung cancer (NSCLC) and the underlying biology of small-cell lung cancer. This review will provide an appreciation for how ongoing scientific findings and technologic advances in molecular pathology are crucial for development of biomarkers, therapeutic agents, clinical trials, and ultimately improved patient care.

Recent Developments of Circulating Tumor Cell Analysis for Monitoring Cutaneous Melanoma Patients

Simple Summary

Circulating tumor cells (CTCs) originating from cutaneous melanoma patients have been studied for several decades as surrogates for real-time clinical status and disease outcomes. Here, we will review clinical studies from the last 15 years that assessed CTCs and disease outcomes for melanoma patients. Assessment of multiple molecular melanoma-associated antigen (MAA) markers by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was the most common assay allowing for the improvement of assay sensitivity, to address tumor heterogeneity, and to predict patient outcomes. Multicenter studies demonstrate the utility of CTC assays reducing the bias observed in single-center trials. Recent development of CTC enrichment platforms has provided reproducible methods. CTC assessment enables both multiple mRNAs and DNAs genomic profiling. CTC provides specific important translational information on tumor progression, prediction of treatment response, and survival outcomes for cutaneous melanoma patients.

Abstract

Circulating tumor cells (CTCs) have been studied using multiple technical approaches for interrogating various cancers, as they allow for the real-time assessment of tumor progression, disease recurrence, treatment response, and tumor molecular profiling without the need for a tumor tissue biopsy. Here, we will review studies from the last 15 years on the assessment of CTCs in cutaneous melanoma patients in relation to different clinical outcomes. The focus will be on CTC detection in blood samples obtained from cutaneous melanoma patients of different clinical stages and treatments utilizing multiple platforms. Assessment of multiple molecular melanoma-associated antigen (MAA) markers by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was the most common assay allowing for the improvement of assay sensitivity, tumor heterogeneity, and to predict patient outcomes. Multicenter studies demonstrate the utility of CTC assays reducing the bias observed in single- center trials. The recent development of CTC enrichment platforms has provided reproducible methods. CTC assessment enables both multiple mRNAs and DNAs genomic aberration profiling. CTC provides specific important translational information on tumor progression, prediction of treatment response, and survival outcomes for cutaneous melanoma patients. The molecular studies on melanoma CTCs have provided and may set standards for other solid tumor CTC analyses.

Detection of ALK Gene Rearrangements in Non-Small Cell Lung Cancer by Immunocytochemistry and Fluorescence in Situ Hybridization on Cytologic Samples

OBJECTIVE

Determination of the molecular status is mandatory for personalized treatment of patients with non-small cell lung carcinoma. The present study was performed to detect anaplastic lymphoma kinase (ALK) rearrangements in pulmonary adenocarcinoma on cytology samples, using immunocytochemistry (ICC) and fluorescence in situ hybridization (FISH) on cell-blocks to assess the diagnostic reliability of these two techniques.

MATERIAL AND METHOD

A total of 50 confirmed lung adenocarcinoma cases were included. In all the 50 cases, ICC was performed for ALK protein expression by using the D5F3 clone on Ventana platform. On the basis of ALK protein expression on ICC, the cases were categorized as ALK positive (2+ or 3+ strong cytoplasmic granular positivity) or negative (negative or 1+ cytoplasmic granular positivity). FISH for detection of ALK gene rearrangement was performed in 7 ALK ICC positive cases and 7 ALK ICC negative cases using the Vysis ALK break apart FISH probe kit.

RESULTS

Based on ICC, 7(14%) cases were ALK positive and 43(86%) were ALK negative. ALK gene rearrangements in lung adenocarcinoma were more commonly seen in non-smokers (31.25%) as compared to smokers (6.25%). Among the ALK-ICC positive cases, FISH demonstrated break apart signal in 5 cases (ALK- ICC positive); however, no break-apart signals were seen in 2 ALK-ICC positive and all the seven ALK-ICC negative cases.

CONCLUSION

Immunocytochemistry on cell- blocks using DF53 clone is a highly sensitive and specific method for the detection of ALK gene rearrangements in lung adenocarcinoma with a greater number of ALK positive cases being detected on ICC as compared to the ALK-FISH.

Understanding Factors Associated With Anaplastic Lymphoma Kinase Testing Delays in Patients With Non-Small Cell Lung Cancer in a Large Real-World Oncology Database

CONTEXT.—

With multiple therapeutic options available for patients with advanced non-small cell lung cancer, the timely ordering and return of results to determine therapy are of critical importance.

OBJECTIVE.—

To assess factors impacting anaplastic lymphoma kinase (ALK) test ordering and time to result delivery.

DESIGN.—

A retrospective study using a de-identified electronic health record database was performed. Postdiagnosis ALK tests (n = 14 657) were analyzed from 14 197 patients with advanced non-small cell lung cancer diagnosed between January 2015 and May 2019. Time from non-small cell lung cancer diagnosis to ALK sample receipt in the laboratory was a surrogate for test order time. Test ordering was considered delayed if order time was more than 20 days. Turnaround time from sample received to test result was calculated and considered delayed if more than 10 days. Multivariable logistic regression was used to assess factors associated with order time and turnaround time delays.

RESULTS.—

Median ALK test order time was 15 days, and 36.4% (5342) of all 14 657 orders were delayed. Factors associated with delays were non-fluorescent in situ hybridization testing, send-out laboratories, testing prior to 2018, nonadenocarcinoma histology, and smoking history. Median turnaround time was 9 days, and 40.3% (5906) of all 14 657 test results were delayed. Non-fluorescent in situ hybridization testing, tissue sample, and orders combining ALK with other biomarkers were associated with delayed ALK result reporting.

CONCLUSIONS.—

This study provides a snapshot of real-world ALK test ordering and reporting time in US community practices. Multiple factors impacted both test ordering time and return of results, revealing opportunities for improvement. It is imperative that patients eligible for targeted therapy be identified in a timely fashion.

New Advances in Liquid Biopsy Technologies for Anaplastic Lymphoma Kinase (ALK)-Positive Cancer

Cancer cells are characterized by high genetic instability, that favors tumor relapse. The identification of the genetic causes of relapse can direct next-line therapeutic choices. As tumor tissue rebiopsy at disease progression is not always feasible, noninvasive alternative methods are being explored. Liquid biopsy is emerging as a non-invasive, easy and repeatable tool to identify specific molecular alterations and monitor disease response during treatment. The dynamic follow-up provided by this analysis can provide useful predictive information and allow prompt therapeutic actions, tailored to the genetic profile of the recurring disease, several months before radiographic relapse. Oncogenic fusion genes are particularly suited for this type of analysis. Anaplastic Lymphoma Kinase (ALK) is the dominant driver oncogene in several tumors, including Anaplastic Large-Cell Lymphoma (ALCL), Non-Small Cell Lung Cancer (NSCLC) and others. Here we review recent findings in liquid biopsy technologies, including ctDNA, CTCs, exosomes, and other markers that can be investigated from plasma samples, in ALK-positive cancers.

Progress and application of circulating tumor cells in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) has the highest morbidity and mortality worldwide among malignant tumors. NSCLC is a great threat to health and well-being. Biopsy is the gold standard to diagnose lung cancer, but traditional biopsy methods cannot fully reflect the true condition of tumors. There is growing evidence that a single-point biopsy fails to reveal the complete landscape of the tumor due to intratumor heterogeneity, but it is impractical to complete multiple biopsies that are separated both spatially and temporally. Liquid biopsy heralds that a new era is coming. Circulating tumor cells (CTCs) are tumor cells that circulate in the peripheral blood after being shed from primary or metastatic tumors. CTCs constitute a considerable portion of a liquid biopsy, which contributes to the diagnosis, assessment of prognosis, and therapy of NSCLC. Herein, this review discusses the technologies for detection and enrichment of CTCs as well as clinical applications involving CTCs.

Circulating tumor cell profiling for precision oncology

Analysis of circulating tumor cells (CTCs) collected from patient's blood offers a broad range of opportunities in the field of precision oncology. With new advances in profiling technology, it is now possible to demonstrate an association between the molecular profiles of CTCs and tumor response to therapy. In this Review, we discuss mechanisms of tumor resistance to therapy and their link to phenotypic and genotypic properties of CTCs. We summarize key technologies used to isolate and analyze CTCs and discuss recent clinical studies that examined CTCs for genomic and proteomic predictors of responsiveness to therapy. We also point out current limitations that still hamper the implementation of CTCs into clinical practice. We finally reflect on how these shortcomings can be addressed with the likely contribution of multiparametric approaches and advanced data analytics.

Inertial Microfluidics Enabling Clinical Research

Fast and accurate interrogation of complex samples containing diseased cells or pathogens is important to make informed decisions on clinical and public health issues. Inertial microfluidics has been increasingly employed for such investigations to isolate target bioparticles from liquid samples with size and/or deformability-based manipulation. This phenomenon is especially useful for the clinic, owing to its rapid, label-free nature of target enrichment that enables further downstream assays. Inertial microfluidics leverages the principle of inertial focusing, which relies on the balance of inertial and viscous forces on particles to align them into size-dependent laminar streamlines. Several distinct microfluidic channel geometries (e.g., straight, curved, spiral, contraction-expansion array) have been optimized to achieve inertial focusing for a variety of purposes, including particle purification and enrichment, solution exchange, and particle alignment for on-chip assays. In this review, we will discuss how inertial microfluidics technology has contributed to improving accuracy of various assays to provide clinically relevant information. This comprehensive review expands upon studies examining both endogenous and exogenous targets from real-world samples, highlights notable hybrid devices with dual functions, and comments on the evolving outlook of the field.

Tumor Evolution and Therapeutic Choice Seen through a Prism of Circulating Tumor Cell Genomic Instability

Circulating tumor cells (CTCs) provide an accessible tool for investigating tumor heterogeneity and cell populations with metastatic potential. Although an in-depth molecular investigation is limited by the extremely low CTC count in circulation, significant progress has been made recently in single-cell analytical processes. Indeed, CTC monitoring through molecular and functional characterization may provide an understanding of genomic instability (GI) molecular mechanisms, which contribute to tumor evolution and emergence of resistant clones. In this review, we discuss the sources and consequences of GI seen through single-cell analysis of CTCs in different types of tumors. We present a detailed overview of chromosomal instability (CIN) in CTCs assessed by fluorescence in situ hybridization (FISH), and we reveal utility of CTC single-cell sequencing in identifying copy number alterations (CNA) oncogenic drivers. We highlight the role of CIN in CTC-driven metastatic progression and acquired resistance, and we comment on the technical obstacles and challenges encountered during single CTC analysis. We focus on the DNA damage response and depict DNA-repair-related dynamic biomarkers reported to date in CTCs and their role in predicting response to genotoxic treatment. In summary, the suggested relationship between genomic aberrations in CTCs and prognosis strongly supports the potential utility of GI monitoring in CTCs in clinical risk assessment and therapeutic choice.

Prospective Multicenter Validation of the Detection of ALK Rearrangements of Circulating Tumor Cells for Noninvasive Longitudinal Management of Patients With Advanced NSCLC

INTRODUCTION

Patients with advanced-stage NSCLC whose tumors harbor an ALK gene rearrangement benefit from treatment with multiple ALK inhibitors (ALKi). Approximately 30% of tumor biopsy samples contain insufficient tissue for successful ALK molecular characterization. This study evaluated the added value of analyzing circulating tumor cells (CTCs) as a surrogate to ALK tissue analysis and as a function of the response to ALKi.

METHODS

We conducted a multicenter, prospective observational study (NCT02372448) of 203 patients with stage IIIB/IV NSCLC across nine French centers, of whom 81 were ALK positive (immunohistochemistry or fluorescence in situ hybridization [FISH]) and 122 ALK negative on paraffin-embedded tissue specimens. Blood samples were collected at baseline and at 6 and 12 weeks after ALKi initiation or at disease progression. ALK gene rearrangement was evaluated with CTCs using immunocytochemistry and FISH analysis after enrichment using a filtration method.

RESULTS

At baseline, there was a high concordance between the detection of an ALK rearrangement in the tumor tissue and in CTCs as determined by immunocytochemistry (sensitivity, 94.4%; specificity 89.4%). The performance was lower for the FISH analysis (sensitivity, 35.6%; specificity, 56.9%). No significant association between the baseline levels or the dynamic change of CTCs and overall survival (hazard ratio = 0.59, 95% confidence interval: 0.24-1.5, p = 0.244) or progression-free survival (hazard ratio = 0.84, 95% confidence interval: 0.44-1.6, p = 0.591) was observed in the patients with ALK-positive NSCLC.

CONCLUSIONS

CTCs can be used as a complementary tool to a tissue biopsy for the detection of ALK rearrangements. Longitudinal analyses of CTCs revealed promise for real-time patient monitoring and improved delivery of molecularly guided therapy in this population.

The role of plasma genotyping in ALK- and ROS1-rearranged lung cancer

Several subsets of non-small cell lung cancer (NSCLC) are defined by the presence of oncogenic rearrangements that result in constitutive activation of a chimeric fusion protein. In NSCLCs that harbor ALK or ROS1 rearrangements, aberrant signaling from these fusion proteins can be overcome by potent and selective tyrosine kinase inhibitors (TKIs). These targeted therapies can induce durable responses and significantly improve prognostic outcomes. Historically, analysis of tissue biopsies was the primary approach to identifying key activating rearrangements. In recent years, non-invasive genotyping of tumor-derived nucleic acids in the circulation has gained ground as a strategy for determining the genetic composition of NSCLCs at diagnosis and throughout the disease course based on prospective and retrospective studies validating the utility of plasma analysis in heterogeneous populations of patients with metastatic NSCLC. Notably, these practice-changing studies predominantly included patients with NSCLCs with oncogenic mutations. Compared to other types of molecular alterations such as mutations and insertions/deletions, oncogenic rearrangements are more complex as they incorporate a variety of fusion partners and diverse breakpoints. Because of this structural complexity, detecting oncogenic rearrangements with plasma assays is more challenging than identifying disease-defining point mutations. In this review, we discuss technical aspects of plasma genotyping strategies and summarize findings from studies exploring plasma genotyping (including ctDNA analysis and profiling of nucleic acids contained in other plasma components) in two rearrangement-driven NSCLC subsets (ALK-rearranged and ROS1-rearranged).

Liquid biopsy for ALK-positive early non-small-cell lung cancer predicts disease relapse

Background: We aimed to determine whether circulating tumor cells (CTCs) and cell-free DNA (cfDNA) aids in prognosis of relapse-free survival (RFS). Methods: Non-small cell lung cancer patients with ALK mutations were recruited prospectively. CTCs and cfDNA were quantified at different time points. RFS was estimated and correlated. Results: Baseline median CTCs and cfDNA were 16 cells and 57 ng/mL and declined to nine cells and 30 ng/mL, respectively, postsurgery in 150 patients. Interestingly, patients without detectable CTCs postsurgery fared better for RFS. cfDNA monitoring showed deviations within 7 months of surgery that were significant predictors for RFS. Conclusion: Short-term monitoring of CTCs and cfDNA variations shows promise for early risk detection and may aid in better disease control.

Molecular and Functional Characterization of Circulating Tumor Cells: From Discovery to Clinical Application

BACKGROUND

One of the objectives for the liquid biopsy is to become a surrogate to tissue biopsies in diagnosis of cancer as a minimally invasive method, with clinical utility in real-time follow-ups of patients. To achieve this goal, it is still necessary to achieve a better understanding of the mechanisms of cancer and the biological principles that govern its behavior, particularly with regard to circulating tumor cells (CTCs).

CONTENT

The isolation, enumeration, detection, and characterization of CTCs have already proven to provide relevant clinical information about patient prognosis and treatment prediction. Moreover, CTCs can be analyzed at the genome, proteome, transcriptome, and secretome levels and can also be used for functional studies in in vitro and in vivo models. These features, taken together, have made CTCs a very valuable biosource.

SUMMARY

To further advance the field and discover new clinical applications for CTCs, several studies have been performed to learn more about these cells and better understand the biology of metastasis. In this review, we describe the recent literature on the topic of liquid biopsy with particular focus on the biology of CTCs.

The Use of Three-Dimensional DNA Fluorescent In Situ Hybridization (3D DNA FISH) for the Detection of Anaplastic Lymphoma Kinase (ALK) in Non-Small Cell Lung Cancer (NSCLC) Circulating Tumor Cells

Tumor tissue biopsy is often limited for non-small cell lung cancer (NSCLC) patients and alternative sources of tumoral information are desirable to determine molecular alterations such as anaplastic lymphoma kinase (ALK) rearrangements. Circulating tumor cells (CTCs) are an appealing component of liquid biopsies, which can be sampled serially over the course of treatment. In this study, we enrolled a cohort of ALK-positive (n = 8) and ALK-negative (n = 12) NSCLC patients, enriched for CTCs using spiral microfluidic technology and performed DNA fluorescent in situ hybridization (FISH) for ALK. CTCs were identified in 12/20 NSCLC patients ranging from 1 to 26 CTCs/7.5 mL blood. Our study revealed that 3D imaging of CTCs for ALK translocations captured a well-defined separation of 3′ and 5′ signals indicative of ALK translocations and overlapping 3′/5′ signal was easily resolved by imaging through the nuclear volume. This study provides proof-of-principle for the use of 3D DNA FISH in the determination of CTC ALK translocations in NSCLC.

Pre-analytical factors affecting the establishment of a single tube assay for multiparameter liquid biopsy detection in melanoma patients

The combination of liquid biomarkers from a single blood tube can provide more comprehensive information on tumor development and progression in cancer patients compared to single analysis. Here, we evaluated whether a combined analysis of circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and circulating cell-free microRNA (miRNA) in total plasma and extracellular vesicles (EV) from the same blood sample is feasible and how the results are influenced by the choice of different blood tubes. Peripheral blood from 20 stage IV melanoma patients and five healthy donors (HD) was collected in EDTA, Streck, and Transfix tubes. Peripheral blood mononuclear cell fraction was used for CTC analysis, whereas plasma and EV fractions were used for ctDNA mutation and miRNA analysis. Mutations in cell-free circulating DNA were detected in 67% of patients, with no significant difference between the tubes. CTC was detected in only EDTA blood and only in 15% of patients. miRNA NGS (next-generation sequencing) results were highly influenced by the collection tubes and could only be performed from EDTA and Streck tubes due to hemolysis in Transfix tubes. No overlap of significantly differentially expressed miRNA (patients versus HD) could be found between the tubes in total plasma, whereas eight miRNA were commonly differentially regulated in the EV fraction. In summary, high-quality CTCs, ctDNA, and miRNA data from a single blood tube can be obtained. However, the choice of blood collection tubes is a critical pre-analytical variable.

Prospective Molecular Profiling of Circulating Tumor Cells from Patients with Melanoma Receiving Combinatorial Immunotherapy

BACKGROUND

Blood molecular profiling of circulating tumor cells (CTCs) can enable monitoring of patients with metastatic melanoma during checkpoint inhibitor immunotherapy (CII) and in combination with targeted therapies. We developed a microfluidics-based CTC platform to explore CTC profiling utility in CII-treated patients with melanoma using a melanoma messenger RNA (mRNA)/DNA biomarker panel.

METHODS

Blood samples (n = 213) were collected prospectively from 75 American Joint Committee on Cancer-staged III/IV melanoma patients during CII treatment and those enriched for CTCs. CTC profiling was performed using 5 known melanoma mRNA biomarkers and BRAF V600E DNA mutation. CTC biomarker status associations with clinical outcomes were assessed.

RESULTS

CTCs were detected in 88% of blood samples from patients with melanoma. CTC-derived biomarkers and clinical variables analyzed using classification and regression tree analysis revealed that a combination of lactate dehydrogenase, CTC-mRNA biomarkers, and tumor BRAF-mutation status was indicative of clinical outcomes for patients with stage IV melanoma (n = 52). The panel stratified low-risk and high-risk patients, whereby the latter had poor disease-free (P = 0.03) and overall survival (P = 0.02). Incorporation of a DNA biomarker with mRNA profiling increased overall CTC-detection capability by 57% compared to mRNA profiling only. RNA sequencing of isolated CTCs identified significant catenin beta 1 (CTNNB1) overexpression (P <0.01) compared to nondisease donor blood. CTC-CTNNB1 was associated with progressive disease/stable disease compared to complete-responder patient status (P = 0.02). Serial CTC profiling identified subclinical disease in patients who developed progressive disease during treatment/follow-up.

CONCLUSIONS

CTC-derived mRNA/DNA biomarkers have utility for monitoring CII, targeted, and combinatorial therapies in metastatic melanoma patients.

Liquid biopsy: one cell at a time

As an alternative target to surgically resected tissue specimens, liquid biopsy has gained much attention over the past decade. Of the various circulating biomarkers, circulating tumor cells (CTCs) have particularly opened new windows into the metastatic cascade, with their functional, biochemical, and biophysical properties. Given the extreme rarity of intact CTCs and the associated technical challenges, however, analyses have been limited to bulk-cell strategies, missing out on clinically significant sources of information from cellular heterogeneity. With recent technological developments, it is now possible to probe genetic material of CTCs at the single-cell resolution to study spatial and temporal dynamics in circulation. Here, we discuss recent transcriptomic profiling efforts that enabled single-cell characterization of patient-derived CTCs spanning diverse cancer types. We further highlight how expression data of these putative biomarkers have advanced our understanding of metastatic spectrum and provided a basis for the development of CTC-based liquid biopsies to track, monitor, and predict the efficacy of therapy and any emergent resistance.

Detection and prognostic relevance of circulating tumour cells (CTCs) in Asian breast cancers using a label-free microfluidic platform

Objectives

We aimed to study the prevalence of CTCs in breast cancer (BC) patients undergoing neoadjuvant or palliative therapy with a label-free microfluidic platform (ClearCell FX), and its prognostic relevance in metastatic BC (mBC).

Materials and methods

Peripheral blood samples were collected from 108 BC patients before starting a new line of treatment (“baseline”), majority of whom had mBC (76/108; 70.4%). CTCs were retrieved by dean flow fractionation that enriched for larger cells, and enumerated using immunofluorescence-based staining. Progression-free survival (PFS) in mBC patients was analysed using Kaplan-Meier method; cox proportional hazard models were used for univariable and multivariable analyses.

Results

The detection rate of CTCs before starting a new line of treatment was 75.9% (n = 108; median: 8 CTCs/7.5 ml blood) at a cut off of ≥2 CTCs. PFS was inferior for mBC patients with baseline CTC count ≥5 CTCs/7.5 ml blood vs. those with < 5 CTCs/7.5 ml blood (median PFS: 4.3 vs. 7.0 months; p-value: 0.037). The prognostic relevance of CTCs was most significant in patients with HER2^- mBC (median PFS: 4.1 vs. 8.3 months; p-value: 0.032), luminal (HR+HER2-) subtype (median PFS: 4.2 vs. 8.3 months; p-value: 0.048), and patients who had one or more prior treatments (median PFS: 4.2 vs. 7.0 months; p-value: 0.02). On multivariable analysis, baseline CTC level (hazard ratio (HR): 1.84, p-value: 0.02) and pre-treatment status (HR: 1.87, p-value: 0.05) were independent predictors of PFS.

Conclusions

This work demonstrates the prognostic significance of CTCs in mBC detected using a label-free size-based enrichment platform.

The potential of monitoring treatment response in non-small cell lung cancer using circulating tumour cells

Introduction: Circulating tumor cell (CTC) counts represent an attractive strategy for monitoring response to therapy in patients with advanced non-small cell lung cancer (NSCLC). Changes in the CTCs number during the treatment have been proposed as a predictive biomarker of response to both chemotherapy and targeted therapies. Profiling of CTCs might also allow the assessment of the dynamics of predictive biomarkers such as EGFR, ALK, ROS1, and PD-L1, and provide relevant information in patients progressing on treatment with targeted agents including immunotherapeutics. Areas covered: A search of peer-reviewed literature in bibliographic databases was undertaken to discuss studies on CTCs and their predictive role in NSCLC. Expert opinion: To date, some challenges limit the clinical utility of CTCs in monitoring the response to treatment in NSCLC. The standardization of techniques for CTCs isolation and characterization and their validation on larger cohorts of patients might help to translate CTCs analysis in the clinic. However, studies on CTCs can provide information on molecular mechanisms involved in NSCLC progression and in the acquired resistance to treatments.

Update on liquid biopsy in clinical management of non-small cell lung cancer

Lung cancer, a leading cause of cancer-related mortality, has a low rate of early diagnosis and a poor prognosis for advanced stages. Recent advances in further mastery of the biology of tumors promote the diagnosis and therapy, especially for non-small cell lung cancer (NSCLC). However, tumor tissue-based information is often not available in most cases due to the invasive and high risk nature of the tumor biopsy procedures. Liquid biopsy, based on the multiple liquid samples including circulating tumor cells (CTC), circulating tumor DNA (ctDNA), and tumor-derived exosome obtained from blood or urine as well as other body fluids, can also provide valuable tumor-related information, playing an important role in management of NSCLC in clinical practice. It is widely believed that concordance of detection for tumor by liquid samples in comparison with tissue biopsy for both early and advanced stage NSCLC patients is optimistic. We herein review the current and future clinical application of liquid biopsy, including early diagnosis and management of precise personalized treatment in lung cancer. The future directions of development for liquid biopsy are also discussed in this review.

Urovysion FISH Could Be Effective and Useful Method to Confirm the Identity of Cultured Circulating Tumor Cells from Bladder Cancer Patients

Objective: To explore whether cultured CTC from bladder-cancer patients originate from bladder cancer and share chromosomal abnormalities, by means of a fluorescence in situ hybridization (FISH) test. Methods: A total of 15 ml of blood was collected from the patients with bladder cancer before treatment began. Isolated CTCs were divided into 5 ml for CTC enumeration and 10 ml for CTC culture. CTCs were counted by immunofluorescent staining with vimentin, cytokeratin, CD45, and DAPI antibody. CTCs were cultured using isolated CTCs in 96-well plates of Mesenchymal Stem Cell Growth Medium for 16~18 days. The resulting cultured CTCs from 20 men with bladder cancer were analyzed by Urovysion FISH. Results: Common gains were on chromosome 3, 7, and 17 in 20 (74.1%), 14 (51.9%), and 20 (74.1%) of 27 patients, respectively. Polysomy was detected on chromosomes 3 and 7 in 9 patients (33.3%). Polysomy involving two chromosomes was observed in 16 (59.3%, chromosome 3 and 17) and 9 patients (33.3%, chromosome 7 and 17) in the same cell. Among the patients with isolated gain, 17 (63.0%) met the positive criteria for Urovysion FISH. Homozygous deletion of 9p21, 5 (18.5%) involved more than 12 cells. Among the different patient cohorts, positive results based on the Urovysion criteria were obtained in cultured CTCs derived from 19 (70.4%) patients. Conclusion: Application of FISH Urovysion to cultured CTCs from bladder cancer could be an effective first step to confirm their origin and sharing of chromosomal abnormalities.

MicroRNA-10a, -210, and -563 as circulating biomarkers for ossification of the posterior longitudinal ligament

BACKGROUND CONTEXT

The presence of ossification of posterior longitudinal ligament (OPLL) can lead to symptomatic spinal cord compression and myelopathy. The surgical approach in patients with myelopathy is influenced by the presence of OPLL. Diagnose of OPLL currently requires computed tomography which incurs a large dose of radiation. Circulating disease-specific microRNAs (miRNAs) may serve as promising diagnostic markers with no radiation and easy accessibility for OPLL patients.

PURPOSE

The purpose of this study is to evaluate the accuracy and significance of OPLL-specific microRNAs in discriminating OPLL from normal and intervertebral disc degenerated (IDD) patients by detecting the microRNAs' plasma level.

STUDY DESIGN/PATIENT SAMPLES

The level of microRNAs in OPLL patients' plasma or serum were detected and compared to that of normal and IDD patients to evaluate the accuracy and significance of diagnosing OPLL.

METHODS

Taking advantage of the high through-put microRNA sequencing data, we selectively tested the ten most differentially regulated microRNAs in patients with: (1) radiologically diagnosed OPLL (n = 68), (2) radiologically diagnosed disc herniated patients with no evidence of OPLL (n = 45), (3) non-OPLL and nonmyelopathy patients (n = 53).The feasibility of the biomarkers in identifying OPLL was assessed through analysis of sensitivity, specificity, accuracy, negative predictive value, positive predictive value, and area under the curve (AUC) values.

RESULTS

Of the ten miRNAs validated, miR-10a-3p, miR-10a-5p, miR-563, miR-210-3p, and miR-218-3p showed significance between OPLL and non-OPLL blood samples. While miR-10a-5p, miR-563, and miR-210-3p showed high accuracy and significance in identifying OPLL from other groups individually, and an index that combines these miRNAs achieved the highest accuracy and AUC among these individual miRNAs.

CONCLUSIONS

Analysis of miR-10a-5p, miR-563, and miR-210-3p may be of important value in diagnosing OPLL. These markers maybe useful in a clinical setting in the early detection of OPLL patients by blood testing.

Phenotypic Characterization of Circulating Lung Cancer Cells for Clinically Actionable Targets

Objectives: In non-small cell lung cancers (NSCLC), tumour biopsy can often be an invasive procedure. The development of a non-invasive methodology to study genetic changes via circulating tumour cells (CTCs) is an appealing concept. Whilst CTCs typically remain as rare cells, improvements in epitope-independent CTC isolation techniques has given rise to a greater capture of CTCs. In this cross sectional study, we demonstrate the capture and characterization of NSCLC CTCs for the clinically actionable markers epidermal growth factor receptor (EGFR) alterations, anaplastic lymphoma kinase (ALK) rearrangements and programmed death ligand-1 (PD-L1) expression. The study identified CTCs/CTC clusters in 26/35 Stage IV NSCLC patients, and subsequently characterized the CTCs for EGFR mutation, ALK status and PD-L1 status. This pilot study demonstrates the potential of a non-invasive fluid biopsy to determine clinically relevant biomarkers in NSCLC.

Circulating Tumor Cell Detection in Lung Cancer: But to What End?

The understanding of the natural history and biology of lung cancer has been enhanced by studies into circulating tumor cells (CTCs). Fundamental and translational research, as well as clinical trials in the characterization and behavior of these cells, have constantly contributed to improving understanding within the domain of thoracic oncology. However, the use of these CTCs as prognostic and predictive biomarkers has not been adopted to the same extent as circulating free DNA (cf-DNA) in plasma, in the daily practice of thoracic oncologists. However, recent technological advances have firmly put the detection and characterization of CTCs in thoracic oncology back on the agenda, and have opened up perspectives for their routine clinical use. This review discusses the major advances of using CTCs in the domain of thoracic oncology, as well as the envisaged short- and long-term prospects.

Circulating tumor cells (CTCs) for the noninvasive monitoring and personalization of non-small cell lung cancer (NSCLC) therapies

Growing evidences for tumor heterogeneity confirm that single-tumor biopsies frequently fail to reveal the widespread mutagenic profile of tumor. Repeated biopsies are in most cases unfeasible, especially in advanced cancers. We describe here how circulating tumor cells (CTCs) isolated from minimally invasive blood sample might inform us about intratumor heterogeneity, tumor evolution and treatment resistance. We also discuss the advances of CTCs research, most notably in molecularly selected non-small cell lung cancer (NSCLC) patients, highlighting challenges and opportunities related to personalized therapy.

ALK testing methods: is there a winner or loser?

INTRODUCTION

Anaplastic lymphoma kinase (ALK) is one of the most attractive molecular targets for the treatment of patients with non-small-cell lung cancer. Treatment with ALK inhibitors is recognized as the standard-of-care for patients with ALK gene rearrangements, but it is important to appropriately select patients who will benefit from such treatment. Areas covered: In this article, we review the evidence regarding ALK testing. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and reverse transcription polymerase chain reaction (RT-PCR) are the representative methods for detecting ALK gene fusions. Among these diagnostic modalities, IHC in particular exhibits high sensitivity and specificity for the detection of ALK fusions when appropriately applied and interpreted. Expert commentary: Discrepancies have been reported between the results of IHC and FISH. However, it was revealed that patients with IHC-positivity and FISH-negativity may respond to alectinib, indicating that IHC can be used as a stand-alone method from a clinical standpoint for the identification of patients eligible for treatment with ALK inhibitors. In addition, differences between ALK variants have been reported to affect the prognosis and efficacy of ALK inhibitor-based treatments, and RT-PCR will likely increase in importance as a complementary tool.

The prognostic significance of circulating tumor cells in head and neck and non-small-cell lung cancer

Tumor biopsy is the gold standard for the assessment of clinical biomarkers for treatment. However, tumors change dynamically in response to therapy, and there remains a need for a more representative biomarker that can be assayed over the course of treatment. Circulating tumor cells (CTCs) may provide clinically important and comprehensive tumoral information that is predictive of treatment response and outcome. Blood samples were processed for CTCs from 56 patients using the ClearCell FX system. Captured cells were phenotyped for CTC clusters and markers for immunotherapy (PD‐L1) CTC chromosomal architecture (ALK, EGFR). CTCs were isolated in 11/23 (47.8%) of head and neck cancer (HNC) patients and 17/33 (51.5%) of non‐small‐cell lung cancer (NSCLC) patients. CTCs were determined to be PD‐L1‐positive in 6/11 (54.4%) HNC and 11/17 (64.7%) NSCLC cases, respectively. 3D chromosomal DNA FISH for ALK and EGFR molecular targets showed better resolution than in 2D when imaging CTCs. HNC CTC‐positive patients had shorter progression‐free survival (PFS) (hazard ratio[HR]: 4.946; 95% confidence internal[CI]:1.571‐15.57; P = 0.0063), and PD‐L1‐positive CTCs were found to be significantly associated with worse outcome ([HR]:5.159; 95% [CI]:1.011‐26.33; P = 0.0485). In the advanced stage NSCLC patient cohort, PFS was not found to be associated with CTCs prior to therapy ([HR]:2.246; 95% [CI]:0.9565‐5.273; P = 0.0632), nor the presence of PD‐L1 expression ([HR]:1.646; 95% [CI]:0.5128‐5.283; P = 0.4023). This study demonstrated that CTCs are predictive of poorer outcomes in HNC and provides distinct and separate utility for CTCs in HNC and NSCLC, which may be more representative of the disease burden and overall survival than the parameters used to measure them.

The Prognostic Role of Circulating Tumor Cells (CTCs) in Lung Cancer

Lung cancer affects over 1. 8 million people worldwide and is the leading cause of cancer related mortality globally. Currently, diagnosis of lung cancer involves a combination of imaging and invasive biopsies to confirm histopathology. Non-invasive diagnostic techniques under investigation include "liquid biopsies" through a simple blood draw to develop predictive and prognostic biomarkers. A better understanding of circulating tumor cell (CTC) dissemination mechanisms offers promising potential for the development of techniques to assist in the diagnosis of lung cancer. Enumeration and characterization of CTCs has the potential to act as a prognostic biomarker and to identify novel drug targets for a precision medicine approach to lung cancer care. This review will focus on the current status of CTCs and their potential diagnostic and prognostic utility in this setting.

ClearCell® FX, a label-free microfluidics technology for enrichment of viable circulating tumor cells

Circulating tumor cells (CTCs) dissociate from primary tumor into the bloodstream, and carry with them cancer's fingerprints as well as the potential to turn aggressive and metastasize. In order to understand CTCs and develop clinical utility, different methods of enrichment and isolation of CTCs can be used. Here, we report the use of a label-free platform, ClearCell® FX which isolates CTCs by their mechanical features and its advantages. The technology utilizes Dean Flow Fractionation (DFF) principle in a spiral microfluidics system to separate the larger CTCs from smaller blood cells. The gentle and fast workflow allows for a range of downstream assays to be performed on the intact CTCs, particularly studies that examine an epithelial cell adhesion molecular (EpCAM)-independent population. Viable, intact cells are also retrievable for development of culture or in vivo models. © 2018 International Society for Advancement of Cytometry.

Identification of circulating tumor cells with EML4-ALK translocation using fluorescence in situ hybridization in advanced ALK-positive patients with lung cancer

Analysis of anaplastic lymphoma kinase (ALK) rearrangement in non-small cell lung cancer (NSCLC) is considered to be a useful tool when considering predictive biomarker detection for evaluating eligibility for targeted therapy. It is not always possible to perform a tumor biopsy in patients. Isolation and culturing of circulating tumor cells (CTCs) may be an alternative to tumor biopsies for the diagnosis of ALK rearrangement. Blood was collected from 22 patients with NSCLC harboring ALK rearrangement and was divided into two groups: One for immunofluorescence staining and the other for culture. Samples were filtered by size and cultured CTCs were analyzed for echinoderm microtubule-associated protein-like 4-ALK translocation using fluorescence in situ hybridization. CTCs positive for epithelial cell adhesion molecule and CTCs exhibiting ALK rearrangement were detected. Therefore, CTCs may be used as a potential alternative method to tissue biopsy for diagnosing ALK rearrangement. Additionally, this method may have clinical applications including serial blood sampling for the development of personalized cancer therapy based on individual genomic information.

Molecular analysis of circulating tumors cells: Biomarkers beyond enumeration

Advances in our molecular understanding of cancer biology have paved the way to an expanding compendium of molecularly-targeted therapies, accompanied by the urgent need for biomarkers that enable the precise selection of the most appropriate therapies for individual cancer patients. Circulating biomarkers such as circulating tumor cells (CTCs) are poised to fill this need, since they are "liquid biopsies" that can be performed non-invasively and serially, and may capture the spectrum of spatial and temporal tumor heterogeneity better than conventional tissue biopsies. Increasing evidence suggests that moving beyond the enumeration of CTCs towards more sophisticated molecular analyses can provide actionable data that may predict and potentially improve clinical outcomes. In this review, we discuss the potential of molecular CTC analyses to serve as prognostic and predictive biomarkers to guide cancer therapy and early cancer detection. As technologies to capture and analyze CTCs continue to increase in sophistication, we anticipate that the potential clinical applications of CTCs will grow exponentially in the coming years.

Blood-based tumor biomarkers in lung cancer for detection and treatment

The therapeutic landscape of lung cancer has expanded significantly over the past decade. Advancements in molecularly targeted therapies, strategies to discover and treat resistance mutations, and development of personalized cancer treatments in the context of tumor heterogeneity and dynamic tumor biology have made it imperative to obtain tumor samples on several different occasions through the course of patient treatment. While this approach is critical to the delivery of optimal cancer treatment, it is fraught with a number of barriers including the need for invasive procedures with associated complications, access to limited amount of tissue, logistical delays in obtaining the biopsy, high healthcare cost, and in many cases inability to obtain tissue because of technically difficult location of the tumor. Given multiple limitations of obtaining tissue samples, the use of blood-based biomarkers ("liquid biopsies") may enable earlier diagnosis of cancer, lower costs by avoiding complex invasive procedures, tailoring molecular targeted treatments, improving patient convenience, and ultimately supplement clinical oncologic decision-making. In this paper, we review various blood-based biomarkers including circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), tumor derived exosomes, tumor educated platelets (TEPs), and microRNA; and highlight current evidence for their use in detection and treatment of lung cancer.

Molecular characterization of circulating tumor cells in lung cancer: moving beyond enumeration

Molecular characterization of tumor cells is a key step in the diagnosis and optimal treatment of lung cancer. However, analysis of tumor samples, often corresponding to small biopsies, can be difficult and does not accurately reflect tumor heterogeneity. Recent studies have shown that isolation of circulating tumor cells (CTCs) is feasible in non-small cell lung cancer patients, even at early disease stages. The amount of CTCs corresponds to the metastatic potential of the tumor and to patient prognosis. Moreover, molecular analyses, even at the single-cell level, can be performed on CTCs. This review describes the technologies currently available for detecting and capturing CTCs, the potential for downstream molecular diagnostics, and the clinical applications of CTCs isolated from lung cancer patients as screening, prognostic, and predictive tools. Main limitations of CTCs are also discussed.

Critical issues in the clinical application of liquid biopsy in non-small cell lung cancer

Current therapeutic options for non-small cell lung cancer (NSCLC) patients are chemotherapy and targeted therapy directed mainly against epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) rearrangements. Targeted therapy relies on the availability of tumor biopsies for molecular profiling at diagnosis and to longitudinally monitor treatment response and resistance development. Unfortunately, tumor biopsy might be invasive, recover poor material of suboptimal quality, and cause sample bias due to tumor heterogeneity. Many studies have illustrated the potential of liquid biopsy as minimal invasive approach to respond to the urgent need for real time monitoring, stratification, and personalized optimized treatment in NSCLC patients. In principle, the liquid biopsy could provide the genetic landscape of primary and metastatic cancerous lesions, detecting "druggable" genomic alterations or associated with treatment resistance. Moreover, it would guarantee the prognostic/predictive biomarkers evaluation in patients for whom biopsies are inaccessible or difficult to repeat. At this regard, the prognostic value of circulating tumor cells (CTCs) in NSCLC patients has been largely investigated, but still their clinical utility as tumor biomarker is hampered by the lack of a consensus on the criteria necessary and sufficient to define them and on the standard operating procedures (SOPs) for their assessment. This review will summarize current developments on liquid biopsy in NSCLC, addressing the technology issues that contribute to the poor ability to track CTCs in the blood of NSCLC patients, thus limiting their extensive use in the clinical practice, and analyzing the solutions adopted to overcome such limits, on the road towards the clinical validation.

Molecular characterization and prognostic significance of circulating tumor cells in patients with non-small cell lung cancer

Circulating tumor cells (CTCs) are rare epithelial cells that can be found in the peripheral blood of cancer patients. A growing body of evidence indicates that CTCs may play a role in non-small cell lung cancer (NSCLC) for diagnosis, therapy monitoring and prognostic purposes. CTCs evaluation could be particularly relevant in this clinical setting, considering that physicians often have difficulty in obtaining an adequate tumor tissue and that patients are not always suitable to receive a re-biopsy. In the current review, we will focus on the molecular characterization and prognostic significance of CTCs in NSCLC patients.

Liquid biopsy genotyping in lung cancer: ready for clinical utility?

Liquid biopsy is a blood test that detects evidence of cancer cells or tumor DNA in the circulation. Despite complicated collection methods and the requirement for technique-dependent platforms, it has generated substantial interest due, in part, to its potential to detect driver oncogenes such as epidermal growth factor receptor (EGFR) mutants in lung cancer. This technology is advancing rapidly and is being incorporated into numerous EGFR tyrosine kinase inhibitor (EGFR-TKI) development programs. It appears ready for integration into clinical care. Recent studies have demonstrated that biological fluids such as saliva and urine can also be used for detecting EGFR mutant DNA through application other user-friendly techniques. This review focuses on the clinical application of liquid biopsies to lung cancer genotyping, including EGFR and other targets of genotype-directed therapy and compares multiple platforms used for liquid biopsy.

Sensitive detection of PD-L1 expression on circulating epithelial tumor cells (CETCs) could be a potential biomarker to select patients for treatment with PD-1/PD-L1 inhibitors in early and metastatic solid tumors

BACKGROUND

The current cancer research strongly focuses on immune therapies, where the PD-1, with its ligands plays an important role. It is known that PD-L1 is frequently up-regulated in a number of different cancers and the relevance of this pathway has been extensively studied and therapeutic approaches targeting PD-1 and PD-L1 have been developed. We used a non-invasive, real-time biopsy for determining PD-L1 and PD-L2 expression in CETCs of solid cancer patients.

METHODS

CETCs were determined from blood of 128 patients suffering from breast (72), prostate (27), colorectal (18) and lung (11) cancer. The number of vital CETCs and the expression of PD-L1 and PD-L2 were investigated using the maintrac^® method.

RESULTS

PD-L1 expressing CETCs were detected in 94.5% of breast, 100% of prostate, 95.4% of colorectal and 82% of lung cancer patients whereas only 75% of breast cancer patients had PD-L2 positive CETCs. In the PD-L1 and PD-L2 expressing patients the cell fraction of PD-L1 positive CETCs is significantly higher than the fraction of PD-L2 positive CETCs (54.6% vs. 28.7%; p<0.001). Breast cancer patients with metastatic disease had significantly more PD-L1 positive CETCs as compared to patients without metastasis (median 75% vs. 61.1%; p<0.05).

CONCLUSION

PD-L1 seems to be a major factor in immune evasion and is highly expressed on CETCs regardless of the type of cancer. Monitoring the frequency of PD-L1 positive CETCs could reflect individual patient's response for an anti-PD-1/PD-L1 therapy and may be a promising target of anticancer treatment.

ALK Status Assessment with Liquid Biopsies of Lung Cancer Patients

Patients with advanced stage non-small cell lung carcinoma (NSCLC) harboring an anaplastic lymphoma kinase ALK gene rearrangement, detected from a tissue sample, can benefit from targeted ALK inhibitor treatment. However, while treatment is initially effective in most cases, relapse or progression occurs due to different resistance mechanisms including mutations in the tyrosine kinase domain of echinoderm microtubule-associated protein-like 4 (EML44)-ALK. The liquid biopsy concept has recently radically changed the clinical care of NSCLC patients, in particular for those harboring an epidermal growth factor receptor (EGFR) gene mutation. Therefore, liquid biopsy is an alternative or complementary method to tissue biopsy for the detection of some resistance mutations in EGFR arising during tyrosine kinase inhibitor treatment. Moreover, in some frail patients, or if the tumor lesion is not accessible to a tissue biopsy, a liquid biopsy can also detect some activating mutations in EGFR on initial assessment. Recent studies have evaluated the possibility of also using a liquid biopsy approach to detect an ALK rearrangement and/or the emergence during inhibitor treatment of some resistance mutations in ALK. These assessments can be performed by studying circulating tumor cells by fluorescent in situ hybridization and by immunocytochemistry and/or after the isolation of RNA from plasma samples, free or associated with platelets. Thus, the liquid biopsy may be a complementary or sometimes alternative method for the assessment of the ALK status in certain NSCLC patients, as well as a non-invasive approach for early detection of ALK mutations. In this review, we highlight the current data concerning the role of the liquid biopsy for the ALK status assessment for NSCLC patients, and we compare the different approaches for this evaluation from blood samples.

Biophysical technologies for understanding circulating tumor cell biology and metastasis

An understanding of cancer evolution in lung cancer with its associated resistance to therapy can only be achieved with repeated sampling and analysis of the cancer. Given the high risks and costs associated with repeat physical biopsy, alternative technologies must be applied. Several modalities exist for analysis and re-analysis of cancer biology. Among them are the CellSearch platform, the CTC chip, and the high-definition CTC platform. While the former is primarily able to provide prognosticating information in the form of CTC enumeration, the latter two have the advantage of serving as a platform to study tumor biology. Techniques for analysis of single cell genomics, as well as protein expression on a single cell basis provide scientists with the capacity to understand cancer cell populations as a collection of individual cells, rather than as an average of all cells. A multimodal combination of circulating tumor DNAs (ctDNAs), CTCs, proteomics, and CTC-derived xenografts (CDXs) to create computational models useful in diagnosis, prognostication, and predictiveness to treatment is likely the future of tailoring individualized cancer care.

Routine clinical use of circulating tumor cells for diagnosis of mutations and chromosomal rearrangements in non-small cell lung cancer-ready for prime-time?

In non-small cell lung cancer (NSCLC), diagnosis of predictive biomarkers for targeted therapies is currently done in small tumor biopsies. However, tumor biopsies can be invasive, in some cases associated with risk, and tissue adequacy, both in terms of quantity and quality is often insufficient. The development of efficient and non-invasive methods to identify genetic alterations is a key challenge which circulating tumor cells (CTCs) have the potential to be exploited for. CTCs are extremely rare and phenotypically diverse, two characteristics that impose technical challenges and impact the success of robust molecular analysis. Here we introduce the clinical needs in this disease that mainly consist of the diagnosis of epidermal growth factor receptor (EGFR) activating alterations and anaplastic lymphoma kinase (ALK) rearrangement. We present the proof-of-concept studies that explore the detection of these genetic alterations in CTCs from NSCLC patients. Finally, we discuss steps that are still required before CTCs are routinely used for diagnosis of EGFR-mutations and ALK-rearrangements in this disease.

Clinical utility of circulating tumor cells in patients with non-small-cell lung cancer

Several different studies have addressed the role of the circulating tumor cells (CTC) in non-small-cell lung cancer (NSCLC). In particular, the potential of CTC analysis in the early diagnosis of NSCLC and in the prediction of the outcome of patients with early and advanced NSCLC have been explored. A major limit of these studies is that they used different techniques for CTC isolation and enumeration, they employed different thresholds to discriminate between high- and low-risk patients, and they enrolled heterogeneous and often small cohort of patients. Nevertheless, the results of many studies are concordant in indicating a correlation between high CTC count and poor prognosis in both early and advanced NSCLC. The reduction of CTC number following treatment might also represent an important indicator of sensitivity to therapy in patients with metastatic disease. Preliminary data also suggest the potential for CTC analysis in the early diagnosis of NSCLC in high-risk individuals. However, these findings need to be confirmed in large prospective trials in order to be transferred to the clinical practice. The molecular profiling of single CTC in NSCLC might provide important information on tumor biology and on the mechanisms involved in tumor dissemination and in acquired resistance to targeted therapies. In this respect, xenografts derived from CTC might represent a valuable tool to investigate these phenomena and to develop novel therapeutic strategies.