Use of cell free DNA in breast oncology

Challenges and Advances in Diagnosis and Treatment of Leptomeningeal Disease (LMD)

Leptomeningeal disease (LMD) is a devastating category of CNS metastasis with a very poor prognosis and limited treatment options. With maximal aggressive therapy, survival times remain short and, without treatment, prognosis is measured in weeks. Both LMD diagnosis and treatment are challenging topics within neuro-oncology. In this review, we discuss the advances in LMD diagnosis with a focus on the role of circulating tumor DNA (ctDNA) and discuss the role of targeted and immunotherapy in LMD treatment.

Detection of gene mutations and gene-gene fusions in circulating cell-free DNA of glioblastoma patients: an avenue for clinically relevant diagnostic analysis

Glioblastoma (GBM) is the most common type of glioma and is uniformly fatal. Currently, tumour heterogeneity and mutation acquisition are major impedances for tailoring personalized therapy. We collected blood and tumour tissue samples from 25 GBM patients and 25 blood samples from healthy controls. Cell‐free DNA (cfDNA) was extracted from the plasma of GBM patients and from healthy controls. Tumour DNA was extracted from fresh tumour samples. Extracted DNA was sequenced using a whole‐genome sequencing procedure. We also collected 180 tumour DNA datasets from GBM patients publicly available at the TCGA/PANCANCER project. These data were analysed for mutations and gene–gene fusions that could be potential druggable targets. We found that plasma cfDNA concentrations in GBM patients were significantly elevated (22.6 ± 5 ng·mL⁻¹), as compared to healthy controls (1.4 ± 0.4 ng·mL⁻¹) of the same average age. We identified unique mutations in the cfDNA and tumour DNA of each GBM patient, including some of the most frequently mutated genes in GBM according to the COSMIC database (TP53, 18.75%; EGFR, 37.5%; NF1, 12.5%; LRP1B, 25%; IRS4, 25%). Using our gene–gene fusion database, ChiTaRS 5.0, we identified gene–gene fusions in cfDNA and tumour DNA, such as KDR–PDGFRA and NCDN–PDGFRA, which correspond to previously reported alterations of PDGFRA in GBM (44% of all samples). Interestingly, the PDGFRA protein fusions can be targeted by tyrosine kinase inhibitors such as imatinib, sunitinib, and sorafenib. Moreover, we identified BCR–ABL1 (in 8% of patients), COL1A1–PDGFB (8%), NIN–PDGFRB (8%), and FGFR1–BCR (4%) in cfDNA of patients, which can be targeted by analogues of imatinib. ROS1 fusions (CEP85L–ROS1 and GOPC–ROS1), identified in 8% of patient cfDNA, might be targeted by crizotinib, entrectinib, or larotrectinib. Thus, our study suggests that integrated analysis of cfDNA plasma concentration, gene mutations, and gene–gene fusions can serve as a diagnostic modality for distinguishing GBM patients who may benefit from targeted therapy. These results open new avenues for precision medicine in GBM, using noninvasive liquid biopsy diagnostics to assess personalized patient profiles. Moreover, repeated detection of druggable targets over the course of the disease may provide real‐time information on the evolving molecular landscape of the tumour.

Identification of MicroRNAs as Diagnostic Biomarkers for Breast Cancer Based on the Cancer Genome Atlas

Breast cancer is the most common cancer among women worldwide. MicroRNAs (miRNAs or miRs) play an important role in tumorigenesis, and thus, they have been identified as potential targets for translational research with diagnostic, prognostic, and therapeutic markers. This study aimed to identify differentially expressed (DE) miRNAs in breast cancer using the Cancer Genome Atlas. The miRNA profiles of 755 breast cancer tissues and 86 adjacent non-cancerous breast tissues were analyzed using Multi Experiment Viewer; miRNA–mRNA network analyses and constructed KEGG pathways with the predicted target genes were performed. The clinical relevance of miRNAs was investigated using area under the receiver operating characteristic curve (AUC) analysis, sensitivity, and specificity. The analysis identified 28 DE miRNAs in breast cancer tissues, including nine upregulated and 19 downregulated miRNAs, compared to non-cancerous breast tissues (p < 0.001). The AUC for each DE miRNA, miR-10b, miR-21, miR-96, miR-99a, miR-100, miR-125b-1, miR-125b-2, miR-139, miR-141, miR-145, miR-182, miR-183, miR-195, miR-200a, miR-337, miR-429, and let-7c, exceeded 0.9, indicating excellent diagnostic performance in breast cancer. Moreover, 1381 potential target genes were predicted using the prediction database tool, miRNet. These genes are related to PD-L1 expression and PD-1 checkpoint in cancer, MAPK signaling, apoptosis, and TNF pathways; hence, they regulate the development, progression, and immune escape of cancer. Thus, these 28 miRNAs can serve as prospective biomarkers for the diagnosis of breast cancer. Taken together, these results provide insight into the pathogenic mechanisms and potential therapies for breast cancer.

CRISPR-dCas9 powered impedimetric biosensor for label-free detection of circulating tumor DNAs

Label-free biosensors which can be integrated into lab-on-a-chip platforms have the advantage of using small volumes for rapid and inexpensive measurements contrary to label-based technologies which are often more costly and time-consuming. In this study, graphene oxide screen printed electrodes (GPHOXE) were modified by deactivated Cas9 (dCas9) proteins and synthetic guide RNA (sgRNA) as the biorecognition receptor for label-free detection of circulating tumor DNAs (ctDNA). This was achieved by detection of a tumor related mutation (PIK3CA exon 9 mutation) via sequence-specific recognition followed by electrochemical impedance spectroscopy (EIS) analysis. The biosensor showed high specificity as there was no impedance signal for other ctDNA sequences, even the single nucleotide mismatch. dCas9-sgRNA modified biosensor demonstrated linear detection limits between 2 and 20 nM for 120 bp ctDNA's in 40 s. The calibration curve showed good linearity, LOD was calculated as 0.65 nM and LOQ was calculated as 1.92 nM. Selectivity and repeatability studies were carried out in real blood samples and the recovery was higher than 96%. In conclusion, dCas9-sgRNA was effectively immobilized and optimized on GPHOXE as the selective biorecognition receptor of this ultrafast impedimetric biosensor. The CRISPR-dCas9 powered impedimetric system showed good selectivity, high repeatability and good recovery properties. This is the first literature to report the use of CRISPR/Cas technology as a label-free tool that can be used in an impedimetric system for detection of ctDNA's.

Will traditional biopsy be substituted by radiomics and liquid biopsy for breast cancer diagnosis and characterisation?

The diagnosis of breast cancer currently relies on radiological and clinical evaluation, confirmed by histopathological examination. However, such approach has some limitations as the suboptimal sensitivity, the long turnaround time for recall tests, the invasiveness of the procedure and the risk that some features of target lesions may remain undetected, making re-biopsy a necessity. Recent technological advances in the field of artificial intelligence hold promise in addressing such medical challenges not only in cancer diagnosis, but also in treatment assessment, and monitoring of disease progression. In the perspective of a truly personalised medicine, based on the early diagnosis and individually tailored treatments, two new technologies, namely radiomics and liquid biopsy, are rising as means to obtain information from diagnosis to molecular profiling and response assessment, without the need of a biopsied tissue sample. Radiomics works through the extraction of quantitative peculiar features of cancer from radiological data, while liquid biopsy gets the whole of the malignancy's biology from something as easy as a blood sample. Both techniques hopefully will identify diagnostic and prognostic information of breast cancer potentially reducing the need for invasive (and often difficult to perform) biopsies and favouring an approach that is as personalised as possible for each patient. Nevertheless, such techniques will not substitute tissue biopsy in the near future, and even in further times they will require the aid of other parameters to be correctly interpreted and acted upon.

M. Dinjens W, Ewing-Graham PC, Smolders R, van Doorn HC, Boere IA, Berns EMJJ, Helleman J, Jansen MPHM. TP53 Mutations in Serum Circulating Cell-Free Tumor DNA As Longitudinal Biomarker for High-Grade Serous Ovarian Cancer

The aim of this study was to determine an optimal workflow to detect TP53 mutations in baseline and longitudinal serum cell free DNA (cfDNA) from high-grade serous ovarian carcinomas (HGSOC) patients and to define whether TP53 mutations are suitable as biomarker for disease. TP53 was investigated in tissue and archived serum from 20 HGSOC patients by a next-generation sequencing (NGS) workflow alone or combined with digital PCR (dPCR). AmpliSeq™-focused NGS panels and customized dPCR assays were used for tissue DNA and longitudinal cfDNAs, and Oncomine NGS panel with molecular barcoding was used for baseline cfDNAs. TP53 missense mutations were observed in 17 tissue specimens and in baseline cfDNA for 4/8 patients by AmpliSeq, 6/9 patients by Oncomine, and 4/6 patients by dPCR. Mutations in cfDNA were detected in 4/6 patients with residual disease and 3/4 patients with disease progression within six months, compared to 5/11 patients with no residual disease and 6/13 patients with progression after six months. Finally, mutations were detected at progression in 5/6 patients, but not during chemotherapy. NGS with molecular barcoding and dPCR were most optimal workflows to detect TP53 mutations in baseline and longitudinal serum cfDNA, respectively. TP53 mutations were undetectable in cfDNA during treatment but re-appeared at disease progression, illustrating its promise as a biomarker for disease monitoring.

Cancer Cell-derived Secretory Factors in Breast Cancer-associated Lung Metastasis: Their Mechanism and Future Prospects

In Breast cancer, Lung is the second most common site of metastasis after the bone. Various factors are responsible for Lung metastasis occurring secondary to Breast cancer. Cancer cellderived secretory factors are commonly known as 'Cancer Secretomes'. They exhibit a prompt role in the mechanism of Breast cancer lung metastasis. They are also major constituents of hostassociated tumor microenvironment. Through cross-talk between cancer cells and the extracellular matrix components, cancer cell-derived extracellular matrix components (CCECs) such as hyaluronan, collagens, laminin and fibronectin cause ECM remodeling at the primary site (breast) of cancer. However, at the secondary site (lung), tenascin C, periostin and lysyl oxidase, along with pro-metastatic molecules Coco and GALNT14, contribute to the formation of pre-metastatic niche (PMN) by promoting ECM remodeling and lung metastatic cells colonization. Cancer cell-derived secretory factors by inducing cancer cell proliferation at the primary site, their invasion through the tissues and vessels and early colonization of metastatic cells in the PMN, potentiate the mechanism of Lung metastasis in Breast cancer. On the basis of biochemical structure, these secretory factors are broadly classified into proteins and non-proteins. This is the first review that has highlighted the role of cancer cell-derived secretory factors in Breast cancer Lung metastasis (BCLM). It also enumerates various researches that have been conducted to date in breast cancer cell lines and animal models that depict the prompt role of various types of cancer cell-derived secretory factors involved in the process of Breast cancer lung metastasis. In the future, by therapeutically targeting these cancer driven molecules, this specific type of organ-tropic metastasis in breast cancer can be successfully treated.

Evaluating the cerebrospinal fluid ctDNA detection by next-generation sequencing in the diagnosis of meningeal Carcinomatosis

Background

Meningeal carcinomatosis (MC) is the most severe form of brain metastasis and causes significant morbidity and mortality. Currently, the diagnosis of MC is routinely confirmed on the basis of clinical manifestation, positive cerebrospinal fluid (CSF) cytology, and/or neuroimaging features. However, negative rate of CSF cytology and neuroimaging findings often result in a failure to diagnose MC from the patients who actually have the disease. Here we evaluate the CSF circulating tumor DNA (ctDNA) in the diagnosis of MC.

Methods

A total of 35 CSF samples were collected from 35 patients with MC for CSF cytology examination, CSF ctDNA extraction and cancer-associated gene mutations detection by next-generation sequencing (NGS) at the same time.

Results

The most frequent primary tumor in this study was lung cancer (26/35, 74%), followed by gastric cancer (2/35, 6%), breast cancer (2/35, 6%), prostatic cancer (1/35, 3%), parotid gland carcinoma (1/35, 3%) and lymphoma (1/35, 3%) while no primary tumor could be found in the remaining 2 patients in spite of using various inspection methods. Twenty-five CSF samples (25/35; 71%) were found neoplastic cells in CSF cytology examination while all of the 35 CSF samples (35/35; 100%) were revealed having detectable ctDNA in which cancer-associated gene mutations were detected. All of 35 patients with MC in the study underwent contrast-enhanced brain MRI and/or CT and 22 neuroimaging features (22/35; 63%) were consistent with MC. The sensitivity of the neuroimaging was 88% (95% confidence intervals [95% CI], 75 to 100) (p = 22/25) and 63% (95% CI, 47 to 79) (p = 22/35) compared to those of CSF cytology and CSF ctDNA, respectively. The sensitivity of the CSF cytology was 71% (95% CI, 56 to 86) (n = 25/35) compared to that of CSF ctDNA.

Conclusions

This study suggests a higher sensitivity of CSF ctDNA than those of CSF cytology and neuroimaging findings. We find cancer-associated gene mutations in ctDNA from CSF of patients with MC at 100% of our cohort, and utilizing CSF ctDNA as liquid biopsy technology based on the detection of cancer-associated gene mutations may give additional information to diagnose MC with negative CSF cytology and/or negative neuroimaging findings.

Circulating tumour DNA (ctDNA) as a biomarker in metachronous melanoma and colorectal cancer- a case report

BACKGROUND

Circulating tumour DNA (ctDNA) has emerged as a promising blood-based biomarker for monitoring disease status of patients with advanced cancers. The presence of ctDNA in the blood is a result of biological processes, namely tumour cell apoptosis and/or necrosis, and can be used to monitor different cancers by targeting cancer-specific mutation.

CASE PRESENTATION

We present the case of a 67 year old Caucasian male that was initially treated with BRAF inhibitors followed by anti-CTLA4 and then anti-PD1 immunotherapy for metastatic melanoma but later developed colorectal cancer. The kinetics of ctDNA derived from each cancer type were monitored targeting BRAF V600R (melanoma) and KRAS G13D (colon cancer), specifically reflected the status of the patient's tumours. In fact, the discordant pattern of BRAF and KRAS ctDNA was significantly correlated with the clinical response of melanoma to pembrolizumab treatment and progression of colorectal cancer noted by PET and/or CT scan. Based on these results, ctDNA can be used to specifically clarify disease status of patients with metachronous cancers.

CONCLUSIONS

Using cancer-specific mutational targets, we report here for the first time the efficacy of ctDNA to accurately provide a comprehensive outlook of the tumour status of two different cancers within one patient. Thus, ctDNA analysis has a potential clinical utility to delineate clinical information in patients with multiple cancer types.

Advanced liquid biopsy technologies for circulating biomarker detection

Liquid biopsy is a new diagnostic concept that provides important information for monitoring and identifying tumor genomes in body fluid samples. Detection of tumor origin biomolecules like circulating tumor cells (CTCs), circulating tumor specific nucleic acids (circulating tumor DNA (ctDNA), circulating tumor RNA (ctRNA), microRNAs (miRNAs), long non-coding RNAs (lnRNAs)), exosomes, autoantibodies in blood, saliva, stool, urine, etc. enables cancer screening, early stage diagnosis and evaluation of therapy response through minimally invasive means. From reliance on painful and hazardous tissue biopsies or imaging depending on sophisticated equipment, cancer management schemes are witnessing a rapid evolution towards minimally invasive yet highly sensitive liquid biopsy-based tools. Clinical application of liquid biopsy is already paving the way for precision theranostics and personalized medicine. This is achieved especially by enabling repeated sampling, which in turn provides a more comprehensive molecular profile of tumors. On the other hand, integration with novel miniaturized platforms, engineered nanomaterials, as well as electrochemical detection has led to the development of low-cost and simple platforms suited for point-of-care applications. Herein, we provide a comprehensive overview of the biogenesis, significance and potential role of four widely known biomarkers (CTCs, ctDNA, miRNA and exosomes) in cancer diagnostics and therapeutics. Furthermore, we provide a detailed discussion of the inherent biological and technical challenges associated with currently available methods and the possible pathways to overcome these challenges. The recent advances in the application of a wide range of nanomaterials in detecting these biomarkers are also highlighted.

Advances in liquid biopsy using circulating tumor cells and circulating cell-free tumor DNA for detection and monitoring of breast cancer

Overview the progress of liquid biopsy using circulating tumor cells (CTCs) and circulating cell-free tumor DNA (cfDNA) to detect and monitor breast cancer. Based on numerous research efforts, the potential value of CTCs and cfDNA in the clinical aspects of cancer has become clear. With the development of next-generation sequencing analysis and newly developed technologies, many technical issues have been resolved, making liquid biopsy widely used in clinical practice. They can be powerful tools for dynamic monitoring of tumor progression and therapeutic efficacy. In the field of breast cancer, liquid biopsy is a research hot spot in recent years, playing a key role in monitoring breast cancer metastasis, predicting disease recurrence and assessing clinical drug resistance. Liquid biopsy has the advantages of noninvasive, high sensitivity, high specificity and real-time dynamic monitoring. Still application is far from reality, but the research and application prospects of CTCs and cfDNA in breast cancer are still worth exploring and discovering. This article reviews the main techniques and applications of CTCs and cfDNA in breast cancer.

Predictive value of circulating cell-free DNA in the survival of breast cancer patients: A systemic review and meta-analysis

PURPOSE

Circulating cell-free DNA (cfDNA) has been reported to predict outcomes in patients with various types of cancer. However, its prognostic value in patients with breast cancer is not well established still now. In this meta-analysis, we evaluated the prognostic role of cfDNA in breast cancer patients.

METHODS

We performed systematic searches in electronic databases to identify studies that evaluated the prognostic value of cfDNA in breast cancer patients. The end points were progression-free survival (PFS) and overall survival (OS). The hazard ratios (HRs) and their 95% confidence intervals (95% CIs) were extracted to assess the prognostic significance of cfDNA. Subgroup analyses were also conducted.

RESULTS

A total of 11 publications involving 1467 patients were included in this meta-analysis. cfDNA was shown to be significantly associated with PFS (HR 2.02, 95% CI 1.51-2.72, P < .001, I = 82%) and OS (HR 1.75, 95% CI 1.01-3.05, P < .001, I = 92%). The results of subgroup analyses also revealed that cfDNA was a good predictor of prognosis in breast cancer patients.

CONCLUSION

Our meta-analysis indicated that cfDNA was associated with poor PFS and OS, thus it may help to predict outcomes of patients with breast cancer. However, further studies are needed to confirm our results.

Molecular Response to Neoadjuvant Chemotherapy in High-Grade Serous Ovarian Carcinoma

While high-grade serous ovarian carcinoma (HGSOC) is the most common histologic subtype of ovarian cancer, significant tumor heterogeneity exists. In addition, chemotherapy induces changes in gene expression and alters the mutational profile. To evaluate the notion that patients with HGSOC could be better classified for optimal treatment based on gene expression, we compared genetic variants [by DNA next-generation sequencing (NGS) using a 50 gene Ion Torrent panel] and gene expression (using the NanoString PanCancer 770 gene Panel) in the tumor from 20 patients with HGSOC before and after neoadjuvant chemotherapy (NACT). NGS was performed on plasma cell free DNA (cfDNA) on a select group of patients (n = 14) to assess the utility of using cfDNA to monitor these changes. A total of 86 genes had significant changes in RNA expression after NACT. Thirty-eight genetic variants (including SNPs) from 6 genes were identified in tumors pre-NACT, while 59 variants from 19 genes were detected in the cfDNA. The number of DNA variants were similar after NACT. Of the 59 variants in the plasma pre-NACT, only 6 persisted, whereas 33 of 38 specific variants in the tumor DNA remained unchanged. Pathway analysis showed the most significant alterations in the cell cycle and DNA damage pathways.Implications: Gene expression profiles at the time of interval debulking provide additional genetic information that could help impact treatment decisions after NACT; although, continued collection and analysis of matched tumor and cfDNA from multiple time points are needed to determine the role of cfDNA in the management of HGSOC. Mol Cancer Res; 16(5); 813-24. ©2018 AACR.

Liquid Biopsy in Clinical Management of Breast, Lung, and Colorectal Cancer

Examination of tumor molecular characteristics by liquid biopsy is likely to greatly influence personalized cancer patient management. Analysis of circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and tumor-derived exosomes, all collectively referred to as “liquid biopsies,” are not only a modality to monitor treatment efficacy, disease progression, and emerging therapy resistance mechanisms, but they also assess tumor heterogeneity and evolution in real time. We review the literature concerning the examination of ctDNA and CTC in a diagnostic setting, evaluating their prognostic, predictive, and monitoring capabilities. We discuss the advantages and limitations of various leading ctDNA/CTC analysis technologies. Finally, guided by the results of clinical trials, we discuss the readiness of cell-free DNA and CTC as routine biomarkers in the context of various common types of neoplastic disease. At this moment, one cannot conclude whether or not liquid biopsy will become a mainstay in oncology practice.

Harnessing a Different Dependency: How to Identify and Target Androgen Receptor-Positive Versus Quadruple-Negative Breast Cancer

The androgen receptor (AR) is a promising therapeutic target for a subset of triple-negative breast cancers (TNBCs) in which AR is expressed. However, the mechanistic action of AR and the degree to which primary and metastatic tumors depend on AR, both before and after conventional treatment, remain to be defined. We discuss preclinical and clinical data for AR+ TNBC, the difficulties in monitoring AR protein levels, new methods for determining AR status, the influence of AR on "stemness" in the context of TNBC, the role of combined inhibition of sex steroid production and AR, and the role of AR in regulation of the immune system. Although the exact role of AR in subsets of TNBC is still being characterized, new therapies that target AR and the production of androgens may provide additional options for patients with TNBC for whom chemotherapy is currently the sole treatment option.

Cell-free circulating tumor DNA analysis for breast cancer and its clinical utilization as a biomarker

Circulating tumor DNA (ctDNA) in the blood of cancer patients contains much information on genetic and epigenetic profiles associated with cancer development, progression, and response to therapy. Analysis of ctDNA provides an opportunity for non-invasive sampling of tumor DNA repetitiously and therefore advance precision medicine. Recent development in massively parallel sequencing and digital genomic techniques support the analytical and clinical validity of ctDNA as a promising 'liquid biopsy' in human cancer. In this review, we discussed the current status of cell-free ctDNA including ctDNA biology, recently developed techniques for ctDNA detection, breast cancer specific detecting strategies, with a focus on clinical applications of ctDNA-based biomarkers in breast oncology.

Somatic Tumor Mutations Detected by Targeted Next Generation Sequencing in Minute Amounts of Serum-Derived Cell-Free DNA

The use of blood-circulating cell-free DNA (cfDNA) as 'liquid-biopsy' is explored worldwide, with hopes for its potential in providing prognostic or predictive information in cancer treatment. In exploring cfDNA, valuable repositories are biobanks containing material collected over time, however these retrospective cohorts have restrictive resources. In this study, we aimed to detect tumor-specific mutations in only minute amounts of serum-derived cfDNA by using a targeted next generation sequencing (NGS) approach. In a retrospective cohort of ten metastatic breast cancer patients, we profiled DNA from primary tumor tissue (frozen), tumor-adjacent normal tissue (formalin-fixed paraffin embedded), and three consecutive serum samples (frozen). Our presented workflow includes comparisons with matched normal DNA or in silico reference DNA to discriminate germline from somatic variants, validation of variants through the detection in at least two DNA samples of an individual, and the use of public databases on variants. By our workflow, we were able to detect a total of four variants traceable as circulating tumor DNA (ctDNA) in the sera of three of the ten patients.

Circulating mutational portrait of cancer: manifestation of aggressive clonal events in both early and late stages

BACKGROUND

Solid tumors residing in tissues and organs leave footprints in circulation through circulating tumor cells (CTCs) and circulating tumor DNAs (ctDNA). Characterization of the ctDNA portraits and comparison with tumor DNA mutational portraits may reveal clinically actionable information on solid tumors that is traditionally achieved through more invasive approaches.

METHODS

We isolated ctDNAs from plasma of patients of 103 lung cancer and 74 other solid tumors of different tissue origins. Deep sequencing using the Guardant360 test was performed to identify mutations in 73 clinically actionable genes, and the results were associated with clinical characteristics of the patient. The mutation profiles of 37 lung cancer cases with paired ctDNA and tumor genomic DNA sequencing were used to evaluate clonal representation of tumor in circulation. Five lung cancer cases with longitudinal ctDNA sampling were monitored for cancer progression or response to treatments.

RESULTS

Mutations in TP53, EGFR, and KRAS genes are most prevalent in our cohort. Mutation rates of ctDNA are similar in early (I and II) and late stage (III and IV) cancers. Mutation in DNA repair genes BRCA1, BRCA2, and ATM are found in 18.1% (32/177) of cases. Patients with higher mutation rates had significantly higher mortality rates. Lung cancer of never smokers exhibited significantly higher ctDNA mutation rates as well as higher EGFR and ERBB2 mutations than ever smokers. Comparative analysis of ctDNA and tumor DNA mutation data from the same patients showed that key driver mutations could be detected in plasma even when they were present at a minor clonal population in the tumor. Mutations of key genes found in the tumor tissue could remain in circulation even after frontline radiotherapy and chemotherapy suggesting these mutations represented resistance mechanisms. Longitudinal sampling of five lung cancer cases showed distinct changes in ctDNA mutation portraits that are consistent with cancer progression or response to EGFR drug treatment.

CONCLUSIONS

This study demonstrates that ctDNA mutation rates in the key tumor-associated genes are clinical parameters relevant to smoking status and mortality. Mutations in ctDNA may serve as an early detection tool for cancer. This study quantitatively confirms the hypothesis that ctDNAs in circulation is the result of dissemination of aggressive tumor clones and survival of resistant clones. This study supports the use of ctDNA profiling as a less-invasive approach to monitor cancer progression and selection of appropriate drugs during cancer evolution.