Analytical validation of a next generation sequencing liquid biopsy assay for high sensitivity broad molecular profiling.
ABSTRACT: Circulating tumor DNA (ctDNA) analysis is being incorporated into cancer care; notably in profiling patients to guide treatment decisions. Responses to targeted therapies have been observed in patients with actionable mutations detected in plasma DNA at variant allele fractions (VAFs) below 0.5%. Highly sensitive methods are therefore required for optimal clinical use. To enable objective assessment of assay performance, detailed analytical validation is required. We developed the InVisionFirst™ assay, an assay based on enhanced tagged amplicon sequencing (eTAm-Seq™) technology to profile 36 genes commonly mutated in non-small cell lung cancer (NSCLC) and other cancer types for actionable genomic alterations in cell-free DNA. The assay has been developed to detect point mutations, indels, amplifications and gene fusions that commonly occur in NSCLC. For analytical validation, two 10mL blood tubes were collected from NSCLC patients and healthy volunteer donors. In addition, contrived samples were used to represent a wide spectrum of genetic aberrations and VAFs. Samples were analyzed by multiple operators, at different times and using different reagent Lots. Results were compared with digital PCR (dPCR). The InVisionFirst assay demonstrated an excellent limit of detection, with 99.48% sensitivity for SNVs present at VAF range 0.25%-0.33%, 92.46% sensitivity for indels at 0.25% VAF and a high rate of detection at lower frequencies while retaining high specificity (99.9997% per base). The assay also detected ALK and ROS1 gene fusions, and DNA amplifications in ERBB2, FGFR1, MET and EGFR with high sensitivity and specificity. Comparison between the InVisionFirst assay and dPCR in a series of cancer patients showed high concordance. This analytical validation demonstrated that the InVisionFirst assay is highly sensitive, specific and robust, and meets analytical requirements for clinical applications.
Project description:Accurate detection of genomic alterations using high-throughput sequencing is an essential component of precision cancer medicine. We characterize the variant allele fractions (VAFs) of somatic single nucleotide variants and indels across 5095 clinical samples profiled using a custom panel, CancerSCAN. Our results demonstrate that a significant fraction of clinically actionable variants have low VAFs, often due to low tumor purity and treatment-induced mutations. The percentages of mutations under 5% VAF across hotspots in EGFR, KRAS, PIK3CA, and BRAF are 16%, 11%, 12%, and 10%, respectively, with 24% for EGFR T790M and 17% for PIK3CA E545. For clinical relevance, we describe two patients for whom targeted therapy achieved remission despite low VAF mutations. We also characterize the read depths necessary to achieve sensitivity and specificity comparable to current laboratory assays. These results show that capturing low VAF mutations at hotspots by sufficient sequencing coverage and carefully tuned algorithms is imperative for a clinical assay.
Project description:BACKGROUND:The analytically sensitive detection of KIT D816V in blood and bone marrow is important for diagnosing systemic mastocytosis (SM). Additionally, precise quantification of the KIT D816V variant allele fraction (VAF) is relevant clinically because it helps to predict multilineage involvement and prognosis in cases of advanced SM. Digital PCR (dPCR) is a promising new method for sensitive detection and accurate quantification of somatic mutations. METHODS:We performed a validation study of dPCR for KIT D816V on 302 peripheral blood and bone marrow samples from 156 patients with mastocytosis for comparison with melting curve analysis after peptide nucleic acid-mediated PCR clamping (clamp-PCR) and allele-specific quantitative real-time PCR (qPCR). RESULTS:dPCR showed a limit of detection of 0.01% VAF with a mean CV of 8.5% and identified the mutation in 90% of patients compared with 70% for clamp-PCR (P < 0.001). Moreover, dPCR for KIT D816V was highly concordant with qPCR without systematic deviation of results, and confirmed the clinical value of KIT D816V VAF measurements. Thus, patients with advanced SM showed a significantly higher KIT D816V VAF (median, 2.43%) compared with patients with indolent SM (median, 0.14%; P < 0.001). Moreover, dPCR confirmed the prognostic significance of a high KIT D816V VAF regarding survival (P < 0.001). CONCLUSIONS:dPCR for KIT D816V provides a high degree of precision and sensitivity combined with the potential for interlaboratory standardization, which is crucial for the implementation of KIT D816V allele burden measurement. Thus, dPCR is suitable as a new method for KIT D816V testing in patients with mastocytosis.
Project description:Robust and analytically validated assays are essential for clinical studies. We outline an analytical validation study of a targeted next-generation sequencing mutation-detection assay used for patient selection in the National Cancer Institute Molecular Profiling-Based Assignment of Cancer Therapy (NCI-MPACT) trial (NCT01827384). Using DNA samples from normal or tumor cell lines and xenografts with known variants, we assessed the sensitivity, specificity, and reproducibility of the NCI-MPACT assay in five variant types: single-nucleotide variants (SNVs), SNVs at homopolymeric (HP) regions (?3 identical bases), small insertions/deletions (indels), large indels (gap ?4 bp), and indels at HP regions. The assay achieved sensitivities of 100% for 64 SNVs, nine SNVs at HP regions, and 11 large indels, 83.33% for six indels, and 93.33% for 15 indels at HP regions. Zero false positives (100% specificity) were found in 380 actionable mutation loci in 96 runs of haplotype map cells. Reproducibility analysis showed 96.3% to 100% intraoperator and 98.1% to 100% interoperator mean concordance in detected variants and 100% reproducibility in treatment selection. To date, 38 tumors have been screened, 34 passed preanalytical quality control, and 18 had actionable mutations for treatment assignment. The NCI-MPACT assay is well suited for its intended investigational use and can serve as a template for developing next-generation sequencing assays for other cancer clinical trial applications.
Project description:INTRODUCTION:Comprehensive genetic cancer profiling using circulating tumor DNA has enabled the detection of National Comprehensive Cancer Network (NCCN) guideline-recommended somatic alterations from a single, non-invasive blood draw. However, reliably detecting somatic variants at low variant allele fractions (VAFs) remains a challenge for next-generation sequencing (NGS)-based tests. We have developed the single-molecule sequencing (SMSEQ) platform to address these challenges. METHODS:The OncoLBx assay utilizes the SMSEQ platform to optimize cell-free DNA extraction and library preparation with variant type-specific calling algorithms to improve sensitivity and specificity. OncoLBx is a pan-cancer panel for solid tumors targeting 75 genes and five microsatellite sites analyzing five classes of NCCN-recommended somatic variants: single-nucleotide variants (SNVs), insertions and deletions (indels), copy number variants (CNVs), fusions and microsatellite instability (MSI). Circulating DNA was extracted from plasma, followed by library preparation using SMSEQ. Analytical validation was performed according to recently published American College of Medical Genetics and Genomics (ACMG)/Association for Molecular Pathology (AMP) guidelines and established the limit of detection (LOD), sensitivity, specificity, accuracy and reproducibility using 126 gold-standard reference samples, healthy donor samples verified by whole-exome sequencing by an external College of American Pathologists (CAP) reference lab and cell lines with known variants. Results were analyzed using a locus-specific modeling algorithm. RESULTS:We have demonstrated that OncoLBx detects VAFs of???0.1% for SNVs and indels,???0.5% for fusions,???4.5 copies for CNVs and???2% for MSI, with all variant types having specificity???99.999%. Diagnostic performance of paired samples displays 80% sensitivity and?>?99.999% clinical specificity. Clinical utility and performance were assessed in 416 solid tumor samples. Variants were detected in 79% of samples, for which 87.34% of positive samples had available targeted therapy.
Project description:Robust identification of genetic alterations is important for the diagnosis and subsequent treatment of tumors. Screening for genetic alterations using tumor tissue samples may lead to biased interpretations because of the heterogeneous nature of the tumor mass. Liquid biopsy has been suggested as an attractive tool for the non-invasive follow-up of cancer treatment outcomes. In this study, we aimed to verify whether the mutations identified in primary tumor tissue samples could be consistently detected in plasma cell-free DNA (cfDNA) by digital polymerase chain reaction (dPCR). We first examined the genetic alteration profiles of three colorectal cancer (CRC) tissue samples by targeted next-generation sequencing (NGS) and identified 11 non-silent amino acid changes across six cancer-related genes (APC, KRAS, TP53, TERT, ARIDIA, and BRCA1). All three samples had KRAS mutations (G12V, G12C, and G13D), which were well-known driver events. Therefore, we examined the KRAS mutations by dPCR. When we examined the three KRAS mutations by dPCR using tumor tissue samples, all of them were consistently detected and the variant allele frequencies (VAFs) of the mutations were almost identical between targeted NGS and dPCR. When we examined the KRAS mutations using the plasma cfDNA of the three CRC patients by dPCR, all three mutations were consistently identified. However, the VAFs were lower (range, 0.166% to 2.638%) than those obtained using the CRC tissue samples. In conclusion, we confirmed that the KRAS mutations identified from CRC tumor tissue samples were consistently detected in the plasma cfDNA of the three CRC patients by dPCR.
Project description:Escherichia coli bacteria are the most common causes of diarrhea and septicemia in calves. Moreover, calves form a major reservoir for transmission of pathogenic E. coli to humans. Systematic reviews and meta-analyses of publications on E. coli as calf pathogens and the role of calves as reservoir have not been done so far. We reviewed studies between 1951 and 2013 reporting the presence of virulence associated factors (VAFs) in calf E. coli and extracted the following information: year(s) and country of sampling, animal number, health status, isolate number, VAF prevalence, serotypes, diagnostic methods, and biological assays. The prevalence of VAFs or E. coli pathotypes was compared between healthy and diarrheic animals and was analyzed for time courses. Together, 106 papers with 25,982 E. coli isolates from 27 countries tested for VAFs were included. F5, F17, and F41 fimbriae and heat-stable enterotoxin (ST) - VAFs of enterotoxigenic E. coli (ETEC) were significantly associated with calf diarrhea. On the contrary, ETEC VAF F4 fimbriae and heat-labile enterotoxin as well as enteropathogenic (EPEC), Shiga toxin-producing (STEC), and enterohemorrhagic E. coli (EHEC) were not associated with diarrhea. The prevalence increased overtime for ST-positive isolates, but decreased for F5- and STEC-positive isolates. Our study provides useful information about the history of scientific investigations performed in this domain so far, and helps to define etiological agents of calf disease, and to evaluate calves as reservoir hosts for human pathogenic E. coli.
Project description:PURPOSE:Guidelines advocate molecular profiling in the evaluation of advanced non-small-cell lung cancer (NSCLC) and support the use of plasma circulating tumor DNA (ctDNA)-based profiling for patients with insufficient tissue. Thorough prospective clinical validation studies of next-generation sequencing (NGS)-based ctDNA assays are lacking. We report the multicentered prospective clinical validation of the InVision ctDNA assay in patients with advanced untreated NSCLC. METHODS:A total of 264 patients with untreated advanced NSCLC were prospectively recruited, and their plasma was analyzed using a ctDNA NGS assay for detection of genomic alterations in 36 commonly mutated genes. Tumor tissue was available in 178 patients for molecular profiling for comparison with plasma profiling. The remaining 86 patients were included to compare ctDNA profiles in patients with and without tissue for profiling. RESULTS:Concordance of InVisionFirst with matched tissue profiling was 97.8%, with 82.9% positive predictive value, 98.5% negative predictive value, 70.6% sensitivity, and 99.2% specificity. Considering specific alterations in eight genes that most influence patient management, the positive predictive value was 97.8%, with 97.1% negative predictive value, 73.9% sensitivity, and 99.8% specificity. Across the entire study, 48 patients with actionable alterations were identified by ctDNA testing compared with only 38 by tissue testing. ctDNA NGS reported either an actionable alteration or an alteration generally considered mutually exclusive for such actionable changes in 53% of patients. CONCLUSION:The liquid biopsy NGS assay demonstrated excellent concordance with tissue profiling in this multicenter, prospective, clinical validation study, with sensitivity and specificity equivalent to Food and Drug Administration-approved single-gene ctDNA assays. The use of plasma-based molecular profiling using NGS led to the detection of 26% more actionable alterations compared with standard-of-care tissue testing in this study.
Project description:As more clinically relevant cancer genes are identified, comprehensive diagnostic approaches are needed to match patients to therapies, raising the challenge of optimization and analytical validation of assays that interrogate millions of bases of cancer genomes altered by multiple mechanisms. Here we describe a test based on massively parallel DNA sequencing to characterize base substitutions, short insertions and deletions (indels), copy number alterations and selected fusions across 287 cancer-related genes from routine formalin-fixed and paraffin-embedded (FFPE) clinical specimens. We implemented a practical validation strategy with reference samples of pooled cell lines that model key determinants of accuracy, including mutant allele frequency, indel length and amplitude of copy change. Test sensitivity achieved was 95-99% across alteration types, with high specificity (positive predictive value >99%). We confirmed accuracy using 249 FFPE cancer specimens characterized by established assays. Application of the test to 2,221 clinical cases revealed clinically actionable alterations in 76% of tumors, three times the number of actionable alterations detected by current diagnostic tests.
Project description:Evaluating treatment failure is critical when deciding to modify antiretroviral therapy (ART). Virologic Assessment Forms (VAFs) were implemented in July 2008 as a prerequisite for ordering viral load. The form requires assessment of clinical and immunologic status.Using the Electronic Medical Record (EMR), we retrospectively evaluated patients who met 2006 WHO guidelines for immunologic failure (?15 years old; on ART ?6 months; CD4 count <baseline OR CD4 count >50% drop from peak OR CD4 persistently <100 cells) at the Lighthouse Trust clinic from December 2007 to December 2009. We compared virologic screening, VAF implementation and ART modification during the same period using Fisher's exact tests and unpaired t-tests as appropriate.Of 7000 enrolled ART patients ?15 years old with at least two CD4 counts, 10% had immunologic failure with a median follow-up time on ART of 1.4 years (IQR: 0.8-2.3). Forty (6%) viral loads were ordered: 14 (35%) were detectable (>400 HIV RNA copies/mL) and one (7%) patient was switched to second-line therapy. Overall, 259 VAFs were completed: 67% for immunologic failure and 33% for WHO Stage 4 condition. Before VAF implementation, 1% of patients had viral loads drawn during routine care, whereas afterwards, 8% did (P<0.0001; 95% CI: 0.03-0.08).Clinicians did not identify a large proportion of immunologic failure patients for screening. Implementation of VAFs produced little improvement in virologic screening during routine care. Better training and monitoring systems are needed.
Project description:Analysis of lung adenocarcinomas for actionable mutations has become standard of care. Here, we report our experience using next generation sequencing (NGS) to examine AKT1, BRAF, EGFR, ERBB2, KRAS, NRAS, and PIK3CA genes in 1006 non-small cell lung cancers in a clinical diagnostic setting. NGS demonstrated high sensitivity. Among 760 mutations detected, the variant allele frequency (VAF) was 2-5% in 33 (4.3%) mutations and 2-10% in 101 (13%) mutations. A single bioinformatics pipeline using Torrent Variant Caller, however, missed a variety of EGFR mutations. Mutations were detected in KRAS (36% of tumors), EGFR (19%) including 8 (0.8%) within the extracellular domain (4 at codons 108 and 4 at codon 289), BRAF (6.3%), and PIK3CA (3.7%). With a broader reportable range, exon 19 deletion and p.L858R accounted for only 36% and 26% of EGFR mutations and p.V600E accounted for only 24% of BRAF mutations. NGS provided accurate sequencing of complex mutations seen in 19% of EGFR exon 19 deletion mutations. Doublet (compound) EGFR mutations were observed in 29 (16%) of 187 EGFR-mutated tumors, including 69% with two non-p.L858R missense mutations and 24% with p.L858 and non-p.L858R missense mutations. Concordant VAFs suggests doublet EGFR mutations were present in a dominant clone and cooperated in oncogenesis. Mutants with predicted impaired kinase, observed in 25% of BRAF-mutated tumors, were associated with a higher incidence of concomitant activating KRAS mutations. NGS demonstrates high analytic sensitivity, broad reportable range, quantitative VAF measurement, single molecule sequencing to resolve complex deletion mutations, and simultaneous detection of concomitant mutations.