Classifying circulating tumor cells to monitor cancer progression

Introduction: The term ‘liquid biopsy’ refers to molecular analysis of a tumor’s genetic features based on circulating genetic material in the peripheral blood derived from circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) and circulating miRNAs, and has emerged as a minimally invasive tool in early cancer diagnosis and disease monitoring. CTCs are believed to originate from the primary tumor and obtain genetic heterogeneity during evolution.

Areas covered: The presence of CTCs has been associated with poor clinical outcome in patients with metastatic breast cancer, lung cancer, colorectal cancer and prostate cancer. In addition, the detection of CTCs in patients with early breast cancer has been shown to represent an independent prognostic factor associated with an unfavorable clinical outcome. Moreover, the longitudinal evaluation of CTCs in patients with early breast cancer may reveal the presence of chemo- and hormone-therapy resistant CTCs which are associated with an increased risk for disease relapse and disease-related death.

Expert commentary: The molecular characterization of CTCs may provide an important tool for the monitoring and the evaluation of treatment efficacy in patients with different tumor types such as breast, prostate, colon, and non-small cell lung cancer.     

Liquid biopsy in the clinical management of bladder cancer: current status and future developments

ABSTRACT

Introduction: The use of liquid biopsy on the blood from solid malignancies provides a convenient way of detecting actionable mutations, monitoring treatment response, detecting early recurrence and prognosticating outcomes. The aim of this review is to discuss the current status and future direction of serum biomarkers in the clinical management of urinary bladder cancer.

Areas covered: This review provides an overview of blood liquid biopsy and bladder cancer using methods of circulating tumors cells, circulating RNA, serum metabolites and cell-free DNA. Recent clinical studies and advances in methodology are emphasized. We performed a literature search using PMC/PubMed with keywords including ‘liquid biopsy’, ‘circulating tumor DNA’, ‘cell-free DNA’, ‘biomarkers’, ‘bladder cancer’ ‘precision medicine’. Additional articles were obtained from the cited references of key articles. An emphasis was placed on recent studies published since 2018.

Expert opinion: Liquid biopsies represent a potential biomarker using cell-free DNA, metabolomic profiles of altered cellular metabolism, circulating cancer cells and RNA. Despite displaying tremendous clinical promise, the current status of the blood liquid biopsies has not reached fruition. However, future investigations should lead the evolution of liquid biomarker into clinical utility for the management of bladder cancer.     

Clinical utility of emerging biomarkers in prostate cancer liquid biopsies

ABSTRACT

Introduction: Prostate cancer (PCa) is one of the most common malignancies in men and a major cause of cancer deaths among men worldwide. Prostate specific antigen (PSA) monitoring and histopathological examination of tumor biopsies remain gold standards in PCa diagnostics. These clinical parameters are not well suited for patient stratification, predicting and monitoring treatment response. On the other hand, liquid biopsies offer a unique opportunity to easily isolate tumor-derived material for longitudinal clinical assessment.

Areas covered: In this review we focus on the clinical application of novel liquid biomarkers that have the potential to monitor and stratify patients in order to achieve better therapeutic effects and improve clinical outcomes. Enumeration and characterization of circulating tumor cells (CTCs), tumor-educated platelets, exosomes, and cell-free nucleic acids have been studied for their clinical utility in PCa diagnostics, prognostics, monitoring treatment response and guiding treatment choice.

Expert opinion: Liquid biomarkers have high potential to be used for prognosis, monitoring treatment response and guiding treatment selection. Although there is a remarkable progress in PCa biomarker discovery, their clinical validation is very limited. Research should be focused on biomarker validation and the incorporation of these biomarkers in clinical practice.     

Liquid biopsy in newly diagnosed patients with locoregional (I-IIIA) non-small cell lung cancer

Introduction: Liquid biopsy is a promising method for the management of lung cancer, but previous studies focused mainly on patients with advanced-stage disease. As the methodology has progressed for the detection of circulating tumor DNA (ctDNA) and its aberrant methylation, researchers are gradually investigating the utility of liquid biopsy in early-stage patients. As a result, liquid biopsy has shown its potential for the application in patients with early- and locally advanced-stage non-small cell lung cancer (NSCLC).

Areas covered: This review summarizes the utility of liquid biopsy in NSCLC and provide an outlook for future development. We focus on the role of ctDNA and its aberrant methylation in patients with stage IA to stageⅢA NSCLC, in the field of early detection and screening, perioperative management, and postoperative surveillance.

Expert opinion: Liquid biopsy has shown the potential for clinical application of early-stage patients but has not been routinely applied yet. The utilization of liquid biopsy will be promoted by improved detection methods and data from well-designed clinical trials. With the development of precision medicine, liquid biopsy will likely play an increasingly important clinical role.     

Noncanonical Wnt as a prognostic marker in prostate cancer: “you can’t always get what you Wnt”

ABSTRACT

Introduction: Wnt signaling is important for normal development, cell proliferation, and cell differentiation. However, aberrations in the pathway can lead to tumorigenesis and cancer progression. Recent genome-wide studies have demonstrated the frequent occurrence of Wnt pathway alterations in prostate cancer. Although alterations in the canonical Wnt pathway in prostate cancer may have an impact on prognosis, recent studies suggest that the noncanonical Wnt pathway also plays an important role in disease progression and treatment resistance.

Areas covered: We review the literature with regard to the potential prognostic significance of noncanonical Wnt signaling in prostate cancer. After a brief overview of the canonical and noncanonical Wnt pathways, we discuss the preclinical and clinical evidence for activation of Wnt signaling in prostate cancer. We focus on clinical evidence for noncanonical Wnt pathway components to serve as potential prognostic biomarkers.

Expert opinion: Although many therapeutic options are available for men with prostate cancer, there remains an unmet need for prognostic and predictive biomarkers to precisely guide clinical management. Early evidence suggests that components of the noncanonical Wnt pathway may serve as prognostic biomarkers. However, prospective validation studies are necessary before these biomarkers can be routinely applied in the clinic.     

Liquid biopsy in germ cell tumors: biology and clinical management

ABSTRACT

Introduction: Liquid biopsy is an increasingly studied approach for optimal and minimally invasive diagnostics of malignant tumors. The aim of this review is to provide evidence and discuss the utility of liquid biopsy in the management of germ cell tumors (GCTs).

Areas covered: Herein, we summarize the evidence on liquid biopsy in GCTs including serum tumor markers, circulating tumor cells, microRNA and cell-free DNA. The search of literature was conducted from Pubmed/Medline, ASCO-meeting library searching for terms ‘liquid biopsy’, ‘germ cell tumors’, ‘circulating tumor cells’, ‘microRNA’, ‘cell-free DNA’. Obtained original studies were included. Reference lists of review articles and key original articles were searched for additional original studies. We included articles published between1990 and 2019.

Expert opinion: Liquid biopsy is a minimally invasive tool using body fluids for diagnostic purposes in cancer. The established value of serum tumor markers may be already considered a liquid biopsy technique in diagnosis of GCTs. Possible near-future refinements in diagnosis of GCTs are emerging. Further information on diagnosis, prognosis and resistance is added with recently described microRNAs, circulating tumor cells and cell-free DNA. While great promise is shown, further large-scale validation is needed to incorporate these novel liquid biopsies into clinical practice.     

The potential of liquid biopsies in gastrointestinal cancer

BackgroundLiquid biopsy is a novel approach for cancer diagnosis, the value of which in human gastrointestinal (GI) cancer has been confirmed by the previous studies. This article summarized the recent advances in liquid biopsy with a focus on novel technologies and the use of it in the screening, monitoring, and treatment of human GI cancer.ContentThe concept of liquid biopsy was first used to define the detection of circulating tumor cells (CTCs) in cancer patients, and has been expanded to other biomarkers in blood and body fluids, such as circulating tumor DNA (ctDNA), extracellular vesicles (EVs) and circulating tumor RNA. If analyzed with proper and advanced techniques like next generation sequencing (NGS) or proteomics, liquid biopsies can open an enormous array of potential biomarkers. The amount changes of target biomarkers and the mutation of genetic materials provide quantitative and qualitative information, which can be utilized clinically for cancer diagnosis and disease monitoring.SummaryAs a highly efficient, minimally invasive, and cost-effective approach to diagnose and evaluate prognosis of GI cancer, liquid biopsy has lots of advantages over traditional biopsy and is promising in future clinical utility. If the challenges are overcome in the near future, liquid biopsy will become a widely available and dependable option.     

Biomarkers of response to advanced prostate cancer therapy

ABSTRACT

Introduction: Prostate cancer (PCa) is one of the most common adult malignancies worldwide, and a major leading cause of cancer-related death in men in Western societies. In the last years, the prognosis of advanced PCa patients has been impressively improved thanks to the development of different therapeutic agents, including taxanes (docetaxel and cabazitaxel), second-generation anti-hormonal agents (abiraterone and enzalutamide), and the radiopharmaceutical Radium-223. However, great efforts are still needed to properly select the most appropriate treatment for each single patient.

Areas covered: Several prognostic or predictive biomarkers have been studied, none of which has an established validated role in daily clinical practice. This paper analyzed the major biomarkers (including PSA, androgen receptor (AR) splice variants, βIII-tubulin, ALP, circulating tumor cells, and DNA repair genes) with a potential prognostic and/or predictive role in advanced PCa patients.

Expert commentary: Surrogate biomarkers – measurable, reproducible, closely associated with tumor behavior and linked to relevant clinical outcomes – are urgently needed to improve PCa patient management.     

Known epigenetic biomarkers for prostate cancer detection and management: exploring the potential of blood-based liquid biopsies

Introduction: Although prostate cancer (PCa) stands as an important cause of cancer-related deaths, a sizeable proportion of diagnosed cases are clinically insignificant. Hence, novel and more specific biomarkers to identify clinically significant PCa are needed. Liquid biopsies offer the potential to accurately identify cancer markers, including PCa. Epigenetic biomarkers such as cell-free DNA and circulating RNAs have emerged as minimally invasive cancer markers.

Areas covered: Herein, we provide an overview of epigenetic biomarkers current state based on a comprehensive review of the relevant literature in blood-based liquid biopsies and challenges/limitations of this new and growing field of cancer biomarkers.

Expert opinion: The epigenetic-based biomarkers characteristics make them attractive to the clinics and their minimally invasive assessment are a promising opportunity for PCa detection/management. The main limitations are the lack of robust validation studies and integrated approaches. Future studies would benefit from a change in focus to a ‘selected PCa detection’.     

The potential use of cell-free-circulating-tumor DNA as a biomarker for prostate cancer

Introduction: We are yet to identify an accurate, precise and non-invasive biomarker for the detection of prostate cancer. It would undoubtedly be useful to have a reliable and cost-effective biomarker to inform clinical practice, in order to make a non-invasive diagnosis and to predict risk of progression to aggressive prostate cancer. Since the detection of cell-free-circulating-tumor DNA in the body fluids of prostate cancer patients, a number of studies have been conducted to assess diagnostic and/or prognostic information.

Areas covered: In this literature review we evaluate the utility of cell-free-circulating-tumor-DNA for the development of a diagnostic and/or prognostic tool for prostate cancer. In addition, we identify potential areas for future research. Results from both quantitative and qualitative studies are presented.

Expert commentary: Evidence for the suitability of a panel of DNA methylation markers for the non-invasive diagnosis of prostate cancer is strong. This panel would likely include the assessment of methylation status in gene promoter regions within the EDNR, GSTP1 and MDR genes. TIMP3 and APC show potential as diagnostic markers and should be further researched. Similarly, quantitation of cell-free-circulating-tumor-DNA in blood and urine requires further investigation.     

Geometric systematic prostate biopsy

Objective: The common sextant prostate biopsy schema lacks a three-dimensional (3D) geometric definition. The study objective was to determine the influence of the geometric distribution of the cores on the detection probability of prostate cancer (PCa).

Methods: The detection probability of significant (>0.5?cm³) and insignificant (<0.2?cm³) tumors was quantified based on a novel 3D capsule model of the biopsy sample. The geometric distribution of the cores was optimized to maximize the probability of detecting significant cancer for various prostate sizes (20–100cm³), number of biopsy cores (6–40 cores) and biopsy core lengths (14–40?mm) for transrectal and transperineal biopsies.

Results: The detection of significant cancer can be improved by geometric optimization. With the current sextant biopsy, up to 20% of tumors may be missed at biopsy in a 20?cm³ prostate due to the schema. Higher number and longer biopsy cores are required to sample with an equal detection probability in larger prostates. Higher number of cores increases both significant and insignificant tumor detection probability, but predominantly increases the detection of insignificant tumors.

Conclusion: The study demonstrates mathematically that the geometric biopsy schema plays an important clinical role, and that increasing the number of biopsy cores is not necessarily helpful.     

The role of ctDNA detection and the potential of the liquid biopsy for breast cancer monitoring

Introduction: Recent advances in deep amplicon sequencing have enabled rapid assessment of somatic mutations and structural changes in multiple cancer genes in DNA isolated from tumour tissues and circulating cell-free DNA (cfDNA). This cfDNA is under investigation as a ‘liquid biopsy’ for the real time monitoring of patients with cancer in a growing number of research studies and clinical trials.

Areas covered: Here we will provide a brief overview of the potential clinical utility of cfDNA profiling for detection and monitoring of patients with breast cancer. The review was conducted in English using PubMed and search terms including ‘breast cancer’, ‘plasma DNA’, ‘circulating cell free DNA’ and ‘circulating tumour DNA’.

Expert commentary: Liquid biopsies through circulating tumor DNA (ctDNA) enable monitoring of patients with breast cancer. The challenge ahead will be to incorporate cfDNA mutation profiling into routine clinical practice to provide patients with the most appropriate and timely treatment.     

An update on liquid biopsy analysis for diagnostic and monitoring applications in non-small cell lung cancer

Introduction: Collection of tumor samples is not always feasible in non-small cell lung cancer (NSCLC) patients, and circulating free DNA (cfDNA) extracted from blood represents a viable alternative. Different sensitive platforms have been developed for genetic cfDNA testing, some of which are already in clinical use. However, several difficulties remain, particularly the lack of standardization of these methodologies.

Areas covered: Here, the authors present a review of the literature to update the applicability of cfDNA for diagnosis and monitoring of NSCLC patients.

Expert commentary: Detection of somatic alterations in cfDNA is already in use in clinical practice and provides valuable information for patient management. Monitoring baseline alterations and emergence of resistance mutations is one of the most important clinical applications and can be used to non-invasively track disease evolution. Today, different technologies are available for cfDNA analysis, including whole-genome or exome sequencing and targeted methods that focus on a selection of genes of interest in a specific disease. In the case of Next Generation Sequencing (NGS) approaches, in depth coverage of candidate mutation loci can be achieved by selecting a limited number of targeted genes.     

Non-coding RNAs as biomarkers in liquid biopsies with a special emphasis on extracellular vesicles in urological malignancies

ABSTRACT

Introduction: Non-coding RNAs (ncRNAs) are important regulators of cellular signaling in tumor-related processes. They can not only be detected in tumor tissues, but also in body fluids. ncRNAs are released into circulation as cell-free RNAs in at least two ways: bound to proteins like Ago2 or packed in extracellular vesicles (EV). Therefore, they have a great potential to serve as biomarkers in liquid biopsies. This review gives an overview of the current knowledge concerning ncRNAs and EVs as putative liquid biomarkers in urological tumor diseases.

Areas covered: Literature was searched for ncRNAs including microRNA, long non-coding RNA, small interfering RNA, small nuclear RNA, small nucleolar RNA and PIWI-interacting RNA in blood (serum, plasma) and urine samples from urological tumor (urothelial, kidney, prostate, testicular germ cell, penile cancer) patients.

Expert opinion: The data demonstrate an important potential of circulating non-coding RNAs as biomarkers in liquid biopsies for diagnosis and follow-up of patients with urological tumors. To translate these markers into clinical practice, independent and prospective validation, standardization of isolation and quantification techniques are inevitable. Another task is the development of predictive ncRNA biomarkers to overcome problems associated with tumor heterogeneity and to select patients individually for systemic therapies.     

Contemporary molecular tests for prognosis and treatment guidance for castration-resistant prostate cancer

Introduction: Currently, clinical factors related to the malignancy and patient-related factors such as performance status and comorbidities are employed to select agents to treat metastatic castration resistant prostate cancer (mCRPC).

Areas covered: This paper covers emerging molecular panels that may be used in the clinic as prognostic or predictive biomarkers to treat mCRPC.

Expert commentary: The expression of androgen receptor variant (AR-V)-7 in circulating tumor cells appears especially promising to select patients for taxane chemotherapy versus androgen inhibitors, abiraterone and enzalutamide. Additionally, the presence of DNA repair alterations such as BRCA alterations are rapidly emerging as a predictive biomarker to develop precision medicine using PARP inhibitors for these patients.     

Immunotherapy for metastatic prostate cancer: where are we at with sipuleucel-T?

Importance of the field: Prostate cancer is the leading malignancy in North American men and despite improvements in treatments 20 – 30% of patients will relapse. Immunotherapy using activated mononuclear cells is a way to harness the body's adaptive immune response to fight metastatic prostate cancer.

Areas covered in this review: In 2005, at least 10 therapeutic cancer vaccines, designed to confer active, specific immunotherapy against tumor-associated antigens, were in clinical trials. These covered potential fields of immunological strategy to overcome castration-resistant prostate cancer.

What the reader will gain: A literature review was performed using the search terms sipuleucel-T, Provenge and APC8015 or APC-8015, and restricted to English language articles from 2000 to 2010. The immunological design and development of sipuleucel-T are summarized. The efficacy and safety of sipuleucel-T are discussed based on current data from clinical trials. Ongoing clinical trials involving sipuleucel-T are summarized.

Take home message: Efficacy and safety with sipuleucel-T has been demonstrated in Phase I/II trials. The latest data from a Phase III trial shows that sipuleucel-T has met the primary endpoint of survival benefit. Further work is needed to understand the mechanisms behind cancer vaccine failure and elucidate the population for whom this vaccine will be suitable.     

Ipilimumab in prostate cancer

Introduction: Immune checkpoint inhibitors, such as ipilimumab, are a new class of immunotherapeutic agents that have shown significant efficacy in melanoma. A number of ongoing clinical trials are investigating the role of ipilimumab in prostate cancer, either alone or in combination with immunomodulating agents such as radiation and chemotherapy, and in combination with cancer vaccines.

Areas covered: This article reviews the molecular basis, preclinical and clinical evidence on the safety and efficacy of ipilimumab in prostate cancer. Medical literature search using MEDLINE and online abstracts database of national meetings form the basis of this article.

Expert opinion: A number of preliminary clinical studies suggest the potential therapeutic utility of immune checkpoint inhibitors such as ipilimumab in prostate cancer. Pending the results of large-scale studies, the rationale of combining ipilimumab with standard anticancer therapeutics such as radiation, cytotoxic chemotherapy and other immunotherapeutic agents can be of great value in reducing mortality and morbidity in prostate cancer.