Plasma circulating tumor DNA as an alternative to metastatic biopsies for mutational analysis in breast cancer

Targeted Next Generation Sequencing as a Reliable Diagnostic Assay for the Detection of Somatic Mutations in Tumours Using Minimal DNA Amounts from Formalin Fixed Paraffin Embedded Material

Background

Targeted Next Generation Sequencing (NGS) offers a way to implement testing of multiple genetic aberrations in diagnostic pathology practice, which is necessary for personalized cancer treatment. However, no standards regarding input material have been defined. This study therefore aimed to determine the effect of the type of input material (e.g. formalin fixed paraffin embedded (FFPE) versus fresh frozen (FF) tissue) on NGS derived results. Moreover, this study aimed to explore a standardized analysis pipeline to support consistent clinical decision-making.

Method

We used the Ion Torrent PGM sequencing platform in combination with the Ion AmpliSeq Cancer Hotspot Panel v2 to sequence frequently mutated regions in 50 cancer related genes, and validated the NGS detected variants in 250 FFPE samples using standard diagnostic assays. Next, 386 tumour samples were sequenced to explore the effect of input material on variant detection variables. For variant calling, Ion Torrent analysis software was supplemented with additional variant annotation and filtering.

Results

Both FFPE and FF tissue could be sequenced reliably with a sensitivity of 99.1%. Validation showed a 98.5% concordance between NGS and conventional sequencing techniques, where NGS provided both the advantage of low input DNA concentration and the detection of low-frequency variants. The reliability of mutation analysis could be further improved with manual inspection of sequence data.

Conclusion

Targeted NGS can be reliably implemented in cancer diagnostics using both FFPE and FF tissue when using appropriate analysis settings, even with low input DNA.

Molecular Testing and the Pathologist's Role in Clinical Trials of Breast Cancer

Molecular characterization of breast cancer is pivotal for identifying new molecular targets and determining the appropriate treatment choices. Advances in molecular profiling technology have given greater insight into this heterogeneous disease, over and above hormone receptor and human epidermal growth factor receptor 2 status. Agents targeting recently characterized molecular biomarkers are under clinical development; the success of these targeted agents is likely to depend on identifying the patient population most likely to benefit. Therefore, clinical trials of breast cancer often require prescreening for, or stratification by, relevant molecular markers or exploratory analyses of biomarkers that can predict or monitor the response to treatment. Consequently, the role of the pathologist has become increasingly important. The key considerations for pathologists include tissue availability, ownership of archival tissue, type of diagnostic/biomarker test required, method of sample processing, concordance between different tests and testing centers, and tumor heterogeneity. In the present review, we explore how pathology is used in current clinical trials of breast cancer and describe the various technologies available for molecular testing. Furthermore, the factors required for the successful application of pathology in clinical trials of breast cancer and the issues that can arise and how these can be circumvented are discussed.

Clinical relevance of circulating KRAS mutated DNA in plasma from patients with advanced pancreatic cancer

We used KRAS mutations to investigate the clinical relevance of circulating tumor DNA (ctDNA) measurements in patients with advanced pancreatic cancer. Fifty-three blood samples were collected from 14 prospectively recruited patients prior to chemotherapy (gemcitabine or FOLFIRINOX) and subsequently every month during treatment. Samples were processed by density centrifugation and plasma DNA isolation. A Peptide-nucleic acid-clamp PCR was then used to detect KRAS mutations (present in >90% of pancreatic cancers) as a surrogate marker for ctDNA. Plasma samples from 29 healthy individuals were analyzed as a reference group. Results were compared to conventional monitoring measures and survival data. Median follow-up time was 3.7 months (range 0.6-12.9 months). Ten (71%) patients had a positive KRAS status in the plasma samples obtained prior to chemotherapy, indicating the presence of ctDNA. Among the patients who were ctDNA-positive before chemotherapy, nine (90%) experienced disease progression during follow-up, compared to one (25%) of four ctDNA-negative patients (P = 0.01). The pre-therapy ctDNA level was a statistically significant predictor of both progression-free and overall survival (P = 0.014 and 0.010, respectively). Of the 14 patients, ten had ≥2 follow-up samples; in several of these patients, the ctDNA level changed substantially during the course of chemotherapy. Changes in ctDNA levels corresponded both with radiological follow-up data and CA19-9 levels for several patients. This pilot study supports the hypothesis that ctDNA may be used as a marker for monitoring treatment efficacy and disease progression in pancreatic cancer patients. Recruitment of more patients is ongoing to corroborate these findings.

Cell-free DNA as a molecular tool for monitoring disease progression and response to therapy in breast cancer patients

Due to the spatial and temporal genomic heterogeneity of breast cancer, genomic sequencing obtained from a single biopsy may not capture the complete genomic profile of tumors. Thus, we propose that cell-free DNA (cfDNA) in plasma may be an alternate source of genomic information to provide comprehensive data throughout a patient's clinical course. We performed a retrospective chart review of 100 patients with stage 4 or high-risk stage 3 breast cancer. The degree of agreement between genomic alterations found in tumor DNA (tDNA) and cfDNA was determined by Cohen's Kappa. Clinical disease progression was compared to mutant allele frequency using a two-sided Fisher's exact test. The presence of mutations and mutant allele frequency was correlated with progression-free survival (PFS) using a Cox proportional hazards model and a log-rank test. The most commonly found genomic alterations were mutations in TP53 and PIK3CA, and amplification of EGFR and ERBB2. PIK3CA mutation and ERBB2 amplification demonstrated robust agreement between tDNA and cfDNA (Cohen's kappa = 0.64 and 0.77, respectively). TP53 mutation and EGFR amplification demonstrated poor agreement between tDNA and cfDNA (Cohen's kappa = 0.18 and 0.33, respectively). The directional changes of TP53 and PIK3CA mutant allele frequency were closely associated with response to therapy (p = 0.002). The presence of TP53 mutation (p = 0.0004) and PIK3CA mutant allele frequency [p = 0.01, HR 1.074 (95 % CI 1.018-1.134)] was excellent predictors of PFS. Identification of selected cancer-specific genomic alterations from cfDNA may be a noninvasive way to monitor disease progression, predict PFS, and offer targeted therapy.

Genetic heterogeneity after first-line chemotherapy in high-grade serous ovarian cancer

BACKGROUND

Most high-grade serous ovarian carcinoma (HGSOC) patients benefit from first-line platinum-based chemotherapy, but progressively develop resistance during subsequent lines. Re-activating BRCA1 or MDR1 mutations can underlie platinum resistance in end-stage patients. However, little is known about resistance mechanisms occurring after a single line of platinum, when patients still qualify for other treatments.

METHODS

In 31 patients with primary platinum-sensitive HGSOC, we profiled tumours collected during debulking surgery before and after first-line chemotherapy using whole-exome sequencing and single nucleotide polymorphism profiling.

RESULTS

Besides germline BRCA1/2 mutations, we observed frequent loss-of-heterozygosity in homologous recombination (HR) genes and mutation spectra characteristic of HR-deficiency in all tumours. At relapse, tumours differed considerably from their primary counterparts. There was, however, no evidence of events reactivating the HR pathway, also not in tumours resistant to second-line platinum. Instead, a platinum score of 13 copy number regions, among other genes including MECOM, CCNE1 and ERBB2, correlated with platinum-free interval (PFI) after first-line therapy, whereas an increase of this score in recurrent tumours predicted the change in PFI during subsequent therapy.

CONCLUSIONS

Already after a single line of platinum, there is huge variability between primary and recurrent tumours, advocating that in HGSOC biopsies need to be collected at relapse to tailor treatment options to the underlying genetic profile. Nevertheless, all primary platinum-sensitive HGSOCs remained HR-deficient, irrespective of whether they became resistant to second-line platinum, further suggesting these tumours qualify for second-line Poly APD ribose polymerase (PARP) inhibitor treatment. Finally, chromosomal instability contributes to acquired resistance after a single line of platinum therapy.

Role of Circulating Cell-Free DNA in Cancers

Liquid biopsy is a term used to describe non-invasive tests, which provide information about disease conditions through analysis of circulating cell-free DNA and circulating tumor cells from peripheral blood samples. In patients with cancer, the concentration of cell-free DNA increases, and structural, sequence, and epigenetic changes to DNA can be observed through the disease process and during therapy. Furthermore, cell-free DNA released by the tumor contains the same variants as those in the tumor cells. Therefore, cell-free DNA allows non-invasive assessment of cancer in real time. This review summarizes the origin of cell-free DNA, recent advancements in the detection of cell-free DNA, a possible role in metastasis, and its importance as a non-invasive diagnostic assay for cancer.

Testing for oncogenic molecular aberrations in cell-free DNA-based liquid biopsies in the clinic: are we there yet?

The optimal choice of cancer therapy depends upon analysis of the tumor genome for druggable molecular alterations. The spatial and temporal intratumor heterogeneity of cancers creates substantial challenges, as molecular profile depends on time and site of tumor tissue collection. To capture the entire molecular profile, multiple biopsies from primary and metastatic sites at different time points would be required, which is not feasible for ethical or economic reasons. Molecular analysis of circulating cell-free DNA offers a novel, minimally invasive method that can be performed at multiple time-points and plausibly better represents the prevailing molecular profile of the cancer. Molecular analysis of this cell-free DNA offers multiple clinically useful applications, such as identification of molecular targets for cancer therapy, monitoring of tumor molecular profile in real time, detection of emerging molecular aberrations associated with resistance to particular therapy, determination of cancer prognosis and diagnosis of cancer recurrence or progression.

Sensitive Detection of Mono- and Polyclonal ESR1 Mutations in Primary Tumors, Metastatic Lesions, and Cell-Free DNA of Breast Cancer Patients

PURPOSE

Given the clinical relevance of ESR1 mutations as potential drivers of resistance to endocrine therapy, this study used sensitive detection methods to determine the frequency of ESR1 mutations in primary and metastatic breast cancer, and in cell-free DNA (cfDNA).

EXPERIMENTAL DESIGN

Six ESR1 mutations (K303R, S463P, Y537C, Y537N, Y537S, D538G) were assessed by digital droplet PCR (ddPCR), with lower limits of detection of 0.05% to 0.16%, in primary tumors (n = 43), bone (n = 12) and brain metastases (n = 38), and cfDNA (n = 29). Correlations between ESR1 mutations in metastatic lesions and single (1 patient) or serial blood draws (4 patients) were assessed.

RESULTS

ESR1 mutations were detected for D538G (n = 13), Y537S (n = 3), and Y537C (n = 1), and not for K303R, S463P, or Y537N. Mutation rates were 7.0% (3/43 primary tumors), 9.1% (1/11 bone metastases), 12.5% (3/24 brain metastases), and 24.1% (7/29 cfDNA). Two patients showed polyclonal disease with more than one ESR1 mutation. Mutation allele frequencies were 0.07% to 0.2% in primary tumors, 1.4% in bone metastases, 34.3% to 44.9% in brain metastases, and 0.2% to 13.7% in cfDNA. In cases with both cfDNA and metastatic samples (n = 5), mutations were detected in both (n = 3) or in cfDNA only (n = 2). Treatment was associated with changes in ESR1 mutation detection and allele frequency.

CONCLUSIONS

ESR1 mutations were detected at very low allele frequencies in some primary breast cancers, and at high allele frequency in metastases, suggesting that in some tumors rare ESR1-mutant clones are enriched by endocrine therapy. Further studies should address whether sensitive detection of ESR1 mutations in primary breast cancer and in serial blood draws may be predictive for development of resistant disease. See related commentary by Gu and Fuqua, p. 1034.

Circulating DNA as biomarker in breast cancer

As the release of tumor-associated DNA into blood circulation is a common event in patients with cancer, screening of plasma or serum DNA may provide information on genetic and epigenetic profiles associated with breast cancer development, progression, and response to therapy. Quantitative testing of circulating DNA can reflect tumor burden, and molecular characterization of circulating DNA can reveal important tumor characteristics relevant to the choice of targeted therapies in individual patients. Contrary to circulating DNA from blood that presents molecular changes in tumor DNA in real time, tissue biopsies can deliver only a spatially and temporally limited snapshot of the heterogeneous tumor. Analyses of circulating DNA might provide prognostic and predictive information and therefore advance personalized medicine. However, standardization of different technical platforms as well as the control of pre-analytical and analytical factors is mandatory before its introduction into clinical practice. In the present review, we discussed technical aspects and clinical relevance of the analyses of circulating plasma/serum DNA in patients with breast cancer.

Clinical and molecular complexity of breast cancer metastases

Clinical oncology is advancing toward a more personalized treatment orientation, making the need to understand the biology of metastasis increasingly acute. Dissecting the complex molecular, genetic and clinical phenotypes underlying the processes involved in the development of metastatic disease, which remains the principal cause of cancer-related deaths, could lead to the identification of more effective prognostication and targeted approaches to prevent and treat metastases. The past decade has witnessed significant progress in the field of cancer metastasis research. Clinical and technological milestones have been reached which have tremendously enriched our understanding of the complex pathways undertaken by primary tumors to progress into lethal metastases and how some of these processes might be amenable to therapy. The aim of this review article is to highlight the recent advances toward unraveling the clinical and molecular complexity of breast cancer metastases. We focus on genes mediating breast cancer metastases and organ-specific tropism, and discuss gene signatures for prediction of metastatic disease. The challenges of translating this information into clinically applicable tools for improving the prognostication of the metastatic potential of a primary breast tumor, as well as for therapeutic interventions against latent and active metastatic disease are addressed.

Characterization of RNA from Exosomes and Other Extracellular Vesicles Isolated by a Novel Spin Column-Based Method

Exosomes and other extracellular vesicles (commonly referred to as EVs) have generated a lot of attention for their potential applications in both diagnostics and therapeutics. The contents of these vesicles are the subject of intense research, and the relatively recent discovery of RNA inside EVs has raised interest in the biological function of these RNAs as well as their potential as biomarkers for cancer and other diseases. Traditional ultracentrifugation-based protocols to isolate EVs are labor-intensive and subject to significant variability. Various attempts to develop methods with robust, reproducible performance have not yet been completely successful. Here, we report the development and characterization of a spin column-based method for the isolation of total RNA from EVs in serum and plasma. This method isolates highly pure RNA of equal or higher quantity compared to ultracentrifugation, with high specificity for vesicular over non-vesicular RNA. The spin columns have a capacity to handle up to 4 mL sample volume, enabling detection of low-abundance transcripts in serum and plasma. We conclude that the method is an improvement over traditional methods in providing a faster, more standardized way to achieve reliable high quality RNA preparations from EVs in biofluids such as serum and plasma. The first kit utilizing this new method has recently been made available by Qiagen as “exoRNeasy Serum/Plasma Maxi Kit”.

Evaluation of targeted therapies in advanced breast cancer: the need for large-scale molecular screening and transformative clinical trial designs

Breast cancer (BC) has been classified into four intrinsic subtypes through seminal studies employing gene expression profiling analysis of primary tumours, namely the luminal A and B subtypes, the human epidermal growth factor receptor 2-like subtype and the basal-like subtype. More recently, the emergence of high-throughput genomic sequencing techniques, such as next-generation or massive parallel sequencing has expanded our understanding of the complex genomic landscapes of BC, with marked intertumour heterogeneity seen among different patients. In addition, increasing evidence indicates intratumour heterogeneity, with molecular differences observed within one patient, both spatially and longitudinally. These phenomena have an impact on the clinical development of molecularly targeted agents, with the classical paradigm of population-based clinical trials being no longer efficient. In the era of genomically driven oncology, three complementary tools can accelerate the clinical development of targeted agents for advanced BC as follows: (i) the implementation of molecular profiling of metastatic tumour lesions, as exemplified by the AURORA (Aiming to Understand the Molecular Aberrations in Metastatic Breast Cancer) programme; (ii) serial assessments of circulating tumour DNA, allowing a more thorough molecular interrogation of metastatic tumour burden; and (iii) new innovative clinical trial designs able to address the challenges of the increasing molecular fragmentation of BC.

Circulating Cell-Free Tumour DNA in the Management of Cancer

With the development of new sensitive molecular techniques, circulating cell-free tumour DNA containing mutations can be identified in the plasma of cancer patients. The applications of this technology may result in significant changes to the care and management of cancer patients. Whilst, currently, these "liquid biopsies" are used to supplement the histological diagnosis of cancer and metastatic disease, in the future these assays may replace the need for invasive procedures. Applications include the monitoring of tumour burden, the monitoring of minimal residual disease, monitoring of tumour heterogeneity, monitoring of molecular resistance and early diagnosis of tumours and metastatic disease.

Short report: Monitoring ESR1 mutations by circulating tumor DNA in aromatase inhibitor resistant metastatic breast cancer

Acquired estrogen receptor gene (ESR1) mutations have been recently reported as a marker of resistance to aromatase inhibitors in hormone receptor positive metastatic breast cancer. We retrospectively considered seven patients treated for metastatic breast cancer with available samples from the primary tumor before any treatment, cryopreserved metastasis removed during progression and concomitant plasmas. All these seven patients were in disease progression after previous exposure to aromatase inhibitors for at least 6 months, and were assessed for ESR1 mutations detection in tumor and circulating DNA. For these patients, Sanger sequencing identified four metastases with clear ESR1 mutation and one possible, whereas digital PCR identified six mutated metastases. Then, under blind conditions and using digital PCR, corresponding circulating ESR1 mutations were successfully detected in four of these six metastatic breast cancer patients. Moreover, in two patients with serial blood samples following treatments exposure, the monitoring of circulating ESR1 mutations clearly predicted disease evolution. In the context of high interest for ESR1 mutations, our results highlight that these acquired recurrent mutations may be tracked in circulating tumor DNA and may be of clinical relevance for metastatic breast cancer patient monitoring.

Methods: for studying pharmacogenetic profiles of combination chemotherapeutic drugs

INTRODUCTION

Molecular and genetic analysis of tumors and individuals has led to patient-centered therapies, through the discovery and identification of genetic markers predictive of drug efficacy and tolerability. Present therapies often include a combination of synergic drugs, each of them directed against different targets. Therefore, the pharmacogenetic profiling of tumor masses and patients is becoming a challenge, and several questions may arise when planning a translational study.

AREAS COVERED

The review presents the different techniques used to stratify oncology patients and to tailor antineoplastic treatments according to individual pharmacogenetic profiling. The advantages of these methodologies are discussed as well as current limits.

EXPERT OPINION

Facing the rapid technological evolution for genetic analyses, the most pressing issues are the choice of appropriate strategies (i.e., from gene candidate up to next-generation sequencing) and the possibility to replicate study results for their final validation. It is likely that the latter will be the major obstacle in the future. However, the present landscape is opening up new possibilities, overcoming those hurdles that have limited result translation into clinical settings for years.

The translational potential of circulating tumour DNA in oncology

The recent understanding of tumour heterogeneity and cancer evolution in response to therapy has raised questions about the value of historical or single site biopsies for guiding treatment decisions. The ability of ctDNA analysis to reveal de novo mutations (i.e., without prior knowledge), allows monitoring of clonal heterogeneity without the need for multiple tumour biopsies. Additionally, ctDNA monitoring of such heterogeneity and novel mutation detection will allow clinicians to detect resistant mechanisms early and tailor treatment therapies accordingly. If ctDNA can be used to detect low volume cancerous states, it will have important applications in treatment stratification post-surgery/radical radiotherapy and may have a role in patient screening. Mutant cfDNA can also be detected in other bodily fluids that are easily accessible and may aid detection of rare mutant alleles in certain cancer types. This article outlines recent advances in these areas.

Translational implications of tumor heterogeneity

Advances in next-generation sequencing and bioinformatics have led to an unprecedented view of the cancer genome and its evolution. Genomic studies have demonstrated the complex and heterogeneous clonal landscape of tumors of different origins and the potential impact of intratumor heterogeneity on treatment response and resistance, cancer progression, and the risk of disease relapse. However, the significance of subclonal mutations, in particular mutations in driver genes, and their evolution through time and their dynamics in response to cancer therapies, is yet to be determined. The necessary tools are now available to prospectively determine whether clonal heterogeneity can be used as a biomarker of clinical outcome and to what extent subclonal somatic alterations might influence clinical outcome. Studies that use longitudinal tissue sampling, integrating both genomic and clinical data, have the potential to reveal the subclonal composition and track the evolution of tumors to address these questions and to begin to define the breadth of genetic diversity in different tumor types and its relevance to patient outcome. Such studies may provide further evidence for drug-resistance mechanisms informing combinatorial, adaptive, and tumor immune therapies placed within the context of tumor evolution.

Endocrine therapy considerations in postmenopausal patients with hormone receptor positive, human epidermal growth factor receptor type 2 negative advanced breast cancers

The standard of care for patients with hormone receptor positive, human epidermal growth factor receptor type 2 negative advanced breast cancer is endocrine therapy. Endocrine agents, including aromatase inhibitors, tamoxifen, and fulvestrant, are often administered alone as first line treatment and demonstrate durable responses with limited side effects. Endocrine resistance represents a major clinical problem. In the future, poly-endocrine therapy and combination therapies with biological agents might become valuable options for the first line treatment of hormone receptor-positive advanced breast cancer. However, it will be critical to develop clinical tools that can reliably identify the subgroup of patients most likely to benefit from endocrine therapy alone, and those who might benefit from alternative approaches. Herein, we will review and discuss current issues in the endocrine treatment of postmenopausal patients with hormone receptor positive, human epidermal growth factor receptor type 2 negative advanced breast cancer.

Biomarkers in Patients with Metastatic Breast Cancer and the PRAEGNANT Study Network

Progress has been made in the treatment of metastatic breast cancer in recent decades, but very few therapies use patient or tumor-specific characteristics to tailor individualized treatment. More than ten years after the publication of the reference human genome sequence, analysis methods have improved enormously, fostering the hope that biomarkers can be used to individualize therapies and offer precise treatment based on tumor and patient characteristics. Biomarkers at every level of the system (genetics, epigenetics, gene expression, micro-RNA, proteomics and others) can be used for this. This has led to changes in clinical study designs, with drug developments often only focusing on small or very small subgroups of patients and tumors. The screening and registration of patients and their molecular tumor data has therefore become very important for the successful completion of clinical studies. This new form of medicine presents particular challenges for patients and physicians. Even in this new age of genome-wide analysis, the focus should still be on the patients' quality of life. This review summarizes recent developments and describes how the PRAEGNANT study network manages the aforementioned medical challenges and changes to create a professional infrastructure for patients and physicians.

Breast Cancer Update 2014 - Focus on the Patient and the Tumour

The therapy for patients with breast cancer has developed markedly in the past ten years. Our understanding of the molecular biology of tumours and the characteristics of the patients has shaped the recent advances. In this review we present the latest knowledge about the therapy for breast cancer. There are new tests and options not only in the field of anti-HER2 therapy but also in the management of triple negative and hormone receptor-positive patients. Comprehension of prognosis and therapeutic response to chemotherapies is little by little helping to define patient groups who will not respond to chemotherapy or who do not need treatment because their prognosis is extremely good. In the field of anti-HER2 therapy, work is continuing on the development of drugs suitable for and able to overcome trastuzumab resistance. For hormone receptor-positive cancers, we now have a better understanding of which therapy groups will benefit from which anti-endocrine drugs, and which will be able to overcome a possible resistance (treatment of the PI3K pathways, inhibition of the cell cycle). Molecular tests are still being evaluated with regard to the clinical situations in which they may have the greatest relevance for therapeutic decision-making; however, evidence is also increasing as to the fields in which good predictions for the prognosis can be obtained. On the whole, more work is needed to promote our understanding of the new developments in diagnostics and therapy and to involve both physicians and patients equally in the procedures.

Targeted deep DNA methylation analysis of circulating cell-free DNA in plasma using massively parallel semiconductor sequencing

AIM

To set up a targeted methylation analysis using semiconductor sequencing and evaluate the potential for studying methylation in circulating cell-free DNA (cfDNA).

MATERIALS & METHODS

Methylation of VIM, FBLN1, LTBP2, HINT2, h19 and IGF2 was analyzed in plasma cfDNA and white blood cell DNA obtained from eight hepatocellular carcinoma patients and eight controls using Ion Torrent™ PGM sequencer.

RESULTS

h19 and IGF2 showed consistent methylation levels and methylation was detected for VIM and FBLN1, whereas LTBP2 and HINT2 did not show methylation for target regions. VIM gene promoter methylation was higher in HCC cfDNA than in cfDNA of controls or white blood cell DNA.

CONCLUSION

Semiconductor sequencing is a suitable method for analyzing methylation profiles in cfDNA. Furthermore, differences in cfDNA methylation can be detected between controls and hepatocellular carcinoma cases, even though due to the small sample set these results need further validation.

Circulating tumor cells and circulating tumor DNA for precision medicine: dream or reality?

Next-generation sequencing studies have provided further evidence to support the notion that cancer is a disease characterized by Darwinian evolution. Today, we often fail to capture this evolution and treatment decisions, even in the metastatic setting, are often based on analysis of primary tumor diagnosed years ago. Currently, this is considered a major reason for treatment failures in cancer care. Recent technological advances in the detection and characterization of circulating tumor cells and circulating tumor DNA might address this and allow for treatment tailoring based on real-time monitoring of tumor evolution. In this review, we summarize the most important recent findings in the field, focusing on challenges and opportunities in moving these tools forward in clinical practice.