Implementation of an NGS‐based sequencing and gene fusion panel for clinical screening of patients with suspected hematologic malignancies

Myelodysplastic Neoplasms (MDS) with Ring Sideroblasts or SF3B1 Mutations: The Improved Clinical Utility of World Health Organization and International Consensus Classification 2022 Definitions, a Single-Centre Retrospective Chart Review

Myelodysplastic neoplasms (MDS) with ring sideroblasts (RS) are diagnosed via bone marrow aspiration in the presence of either (i) ≥15% RS or (ii) 5-14% RS and an SF3B1 mutation. In the MEDALIST trial and in an interim analysis of the COMMANDS trial, lower-risk MDS-RS patients had decreased transfusion dependency with luspatercept treatment. A total of 6817 patients with suspected hematologic malignancies underwent molecular testing using a next-generation-sequencing-based genetic assay and 395 MDS patients, seen at our centre from 1 January 2018 to 31 May 2023, were reviewed. Of these, we identified 39 evaluable patients as having lower-risk MDS with SF3B1 mutations: there were 20 (51.3%) males and 19 (48.7%) females, with a median age of 77 years (range of 57 to 92). Nineteen (48.7%) patients had an isolated SF3B1 mutation with a mean variant allele frequency of 35.2% +/- 8.1%, ranging from 7.4% to 46.0%. There were 29 (74.4%) patients with ≥15% RS, 6 (15.4%) with 5 to 14% RS, one (2.6%) with 1% RS, and 3 (7.7%) with no RS. Our study suggests that a quarter of patients would be missed based on the morphologic criterion of only using RS greater than 15% and supports the revised 2022 definitions of the World Health Organization (WHO) and International Consensus Classification (ICC), which shift toward molecularly defined subtypes of MDS and appropriate testing.

Performance evaluation and clinical impact of the Oncomine Myeloid Research Assay for gene expression analysis in myeloid haematologic malignancies

AIM

Gene expression analysis facilitates the detection of diagnostic and prognostic biomarkers for myeloid haematological malignancies. The Oncomine Myeloid Research Assay (OMA; Thermo Fisher Scientific, Massachusetts, USA) provides a comprehensive analysis of gene expression of five target genes, along with gene alteration and fusion. Here, we present the performance of the OMA for gene expression analysis.

METHODS

In total, 53 RNA samples from patients diagnosed with acute myeloid leukaemia (AML) or myelodysplastic syndrome were included. Of these 53 samples, 3 were evaluated for reproducibility and 50 were evaluated for comparison with RNA-sequencing (RNA-seq). The prognostic impact of the gene expression profile produced by both OMA and RNA-seq in AML was investigated using follow-up data from 33 patients with AML.

RESULTS

The OMA showed good intrarun and interrun reproducibility. Compared with the RNA-seq results, high correlations were found in BAALC, MECOM and WT1 (all r>0.9), with moderate correlations in MYC (r=0.75, p<0.001) and SMC1A (r=0.42, p=0.002). The agreement between OMA and RNA-seq in classifying the dysregulated expression group was almost perfect, except for SMC1A (κ=0.175). Among these five genes, only BAALC showed a significant clinical impact in patients with AML. Patients with high BAALC expression showed significantly shorter overall survival based on both OMA (p=0.037) and RNA-seq (p=0.003).

CONCLUSIONS

OMA gene expression analysis offers reproducible and accurate gene expression data for most targeted genes and demonstrates the utility of BAALC expression as a prognostic marker in AML.

Rapid and Automated Semiconductor-Based Next-Generation Sequencing for Simultaneous Detection of Somatic DNA and RNA Aberrations in Myeloid Neoplasms

Evaluation of suspected myeloid neoplasms involves testing for recurrent, diagnostically and therapeutically relevant genetic alterations. Current molecular testing requires multiple technologies, different domains of expertise, and unconnected workflows, resulting in variable, lengthy turnaround times that can delay treatment. To address this unmet clinical need, we evaluated the Oncomine Myeloid Assay GX panel on the Ion Torrent Genexus platform, a rapid, integrated nucleic acid to report next-generation sequencing platform for detecting clinically relevant genetic aberrations in myeloid disorders. Specimens included synthetic DNA (101 targets) and RNA (9 targets) controls and real-world nucleic acid material derived from bone marrow or peripheral blood samples (40 patients). Ion Torrent Genexus results and performance indices were compared with those obtained from clinically validated genomic testing workflows in 2 separate clinical laboratories. The Ion Torrent Genexus identified 100% of DNA and RNA control variants. For primary patient specimens, the Ion Torrent Genexus reported 82 of 107 DNA variants and 19 of 19 RNA gene fusions identified on clinically validated assays, yielding an 80% overall detection rate. Reanalysis of exported, unfiltered Ion Torrent Genexus data revealed 15 DNA variants not called by the filtered on-board bioinformatics pipeline, yielding a 92% potential detection rate. These results hold promise for the implementation of an integrated next-generation sequencing system to rapidly detect genetic aberrations, facilitating accurate, genomics-based diagnoses and accelerated time to precision therapies in myeloid neoplasms.

Mutational Landscape of Patients Referred for Elevated Hemoglobin Level

Background: Since the identification of JAK2 V617F and exon 12 mutations as driver mutations in polycythemia vera (PV) in 2005, molecular testing of these mutations for patients with erythrocytosis has become a routine clinical practice. However, the incidence of myeloid mutations other than the common JAK2 V617F mutation in unselected patients referred for elevated hemoglobin is not well studied. This study aimed to characterize the mutational landscape in a real-world population of patients referred for erythrocytosis using a targeted next-generation sequencing (NGS)-based assay. Method: A total of 529 patients (hemoglobin levels >160 g/L in females or >165 g/L in males) were assessed between January 2018 and May 2021 for genetic variants using the Oncomine Myeloid Research Assay (ThermoFisher Scientific, Waltham, MA, USA) targeting 40 key genes with diagnostic and prognostic implications in hematological conditions (17 full genes and 23 genes with clinically relevant "hotspot" regions) and a panel of 29 fusion driver genes (>600 fusion partners). Results:&nbsp;JAK2 mutations were detected in 10.9% (58/529) of patients, with 57 patients positive for JAK2 V617F, while one patient had a JAK2 exon 12 mutation. Additional mutations were detected in 34.5% (20/58) of JAK2-positive patients: TET2 (11; 19%), DNMT3A (2;3.4%), ASXL1 (2; 3.4%), SRSF2 (2; 3.4%), BCOR (1; 1.7%), TP53 (1; 1.7%), and ZRSR2 (1; 1.7%). Diagnosis of PV was suspected in 2 JAK2-negative patients based on the 2016 World Health Organization (WHO) diagnostic criteria. Notably, one patient carried mutations in the SRSF2 and TET2 genes, and the other patient carried mutations in the SRSF2, IDH2, and ASXL1 genes. Three JAK2-negative patients with elevated hemoglobin who tested positive for BCR/ABL1 fusion were diagnosed with chronic myeloid leukemia (CML) and excluded from further analysis. The remaining 466 JAK2-negative patients were diagnosed with secondary erythrocytosis and mutations were found in 6% (28/466) of these cases. Conclusion: Mutations other than JAK2 mutations were frequently identified in patients referred for erythrocytosis, with mutations in the TET2, DNMT3A, and ASXL1 genes being detected in 34.5% of JAK2-positive PV patients. The presence of additional mutations, such as ASXL1 mutations, in this population has implications for prognosis. Both the incidence and mutation type identified in patients with secondary erythrocytosis likely reflects incidental, age-associated clonal hematopoiesis of indeterminate potential (CHIP).

Diagnostic Impact of Next-Generation Sequencing Panels for Lymphoproliferative Neoplasms on Small-Volume Biopsies

OBJECTIVES

We investigated the feasibility and utility of next-generation sequencing (NGS)-based targeted somatic mutation panels and IG/TR gene rearrangement assays in the diagnosis of lymphoproliferative disorders (LPDs) in small-volume biopsies.

MATERIALS

We performed a retrospective, single-institution review of all NGS assays requested over a 3-year period by hematopathologists for diagnostic purposes on small-volume biopsies.

RESULTS

We identified 59 small-volume biopsies. The TR assay was most commonly requested (42 [71%]), followed by the somatic mutation panel (32 [54%]) and IG assay (26 [44%]). NGS studies were associated with a change in the diagnostic line in about half of cases (28 [47%]) and in a change in the likelihood of a diagnosis in a further 16 cases (27%); there was no diagnostic impact of NGS testing in 15 cases (25%).

CONCLUSIONS

Implementation of NGS panel somatic mutation or IG/TR gene rearrangement assays on small-volume biopsies contributes to the diagnosis of LPDs in the majority of select cases for diagnostic purposes. The molecular diagnosis is considered in the context of the clinical, histologic, and immunophenotypic findings and does not by itself lead to a definitive diagnosis in small-volume biopsies.

Clinical Utility of Implementing a Frontline NGS-Based DNA and RNA Fusion Panel Test for Patients with Suspected Myeloid Malignancies

BACKGROUND

The use of molecular genetic biomarkers is rapidly advancing to aid diagnosis, prognosis, and clinical management of hematological disorders. We have implemented a next-generation sequencing (NGS) assay for detection of genetic variants and fusions as a frontline test for patients suspected with myeloid malignancy. In this study, we summarize the findings and assess the clinical impact in the first 1613 patients tested.

METHODS

All patients were assessed using NGS based Oncomine Myeloid Research Assay (ThermoFisher) including 40 genes (17 full genes and 23 genes with clinically relevant "hotspot" regions), along with a panel of 29 fusion driver genes (including over fusion 600 partners).

RESULTS

Among 1613 patients with suspected myeloid malignancy, 43% patients harbored at least one clinically relevant variant: 91% (90/100) in acute myeloid leukemia patients, 71.7% (160/223) in myelodysplastic syndrome (MDS), 77.5% (308/397) in myeloproliferative neoplasm (MPN), 83% (34/41) in MPN/MDS, and 100% (40/40) in chronic myeloid leukemia patients. Comparison of NGS and cytogenetics results revealed a high degree of concordance in gene fusion detection.

CONCLUSIONS

Our findings demonstrate clinical utility and feasibility of integrating a NGS-based gene mutation and fusion testing assay as a frontline diagnostic test in a large reported cohort of patients with suspected myeloid malignancy, in a clinical laboratory setting. Overlap with cytogenetic test results provides opportunity for testing reduction and streamlining.

The value of next-generation sequencing in routine diagnostics and management of patients with cytopenia

INTRODUCTION

We performed a single-center study of real-world health data to investigate the direct clinical consequence of targeted next-generation sequencing (NGS) results integrated in the clinicopathological evaluation of patients with cytopenia suspected of myelodysplastic syndrome (MDS).

METHODS

The study included 87 newly referred patients, who had a bone marrow examination, which included targeted NGS analysis. NGS was requested at the discretion of either examining pathologist or hematologist. Data were collected retrospectively from patient files including pathology reports with integrated NGS results.

RESULTS

The NGS results had a diagnostic impact in 67 cases (77%) when combining both histopathological and final clinical evaluation and provided prognostic value in 19 cases (22%). NGS supported a confident or tentative histopathological diagnosis in 52 cases (60%). Twenty cases (23%) had a final diagnosis of either Clonal Cytopenia of Undetermined Significance (CCUS) or Idiopathic Cytopenia of Undetermined Significance (ICUS). In 4 cases, NGS results affected the choice of principal treatment strategy, including considerations of allotransplantation. Twenty-one patients (24%) could be discharged to primary care physician.

CONCLUSION

In a multidisciplinary clinicopathological real-world setting, NGS analysis of bone marrow samples from selected patients contributed substantially to the diagnostic evaluation and management of patients with cytopenia suspected of MDS. Consequently, we have now included NGS analysis in most routine bone marrow examinations from patients with MDS or unexplained cytopenia.

Reducing cytogenetic testing in the era of next generation sequencing: Are we choosing wisely?

INTRODUCTION

In most laboratories, next generation sequencing (NGS) has been added without consideration for redundancy compared to conventional cytogenetics (CG). We tested a streamlined approach to genomic testing in patients with suspected myeloid and plasma cell neoplasms using next generation sequencing ("NGS first") as the primary testing modality and limiting cytogenetics (CG) to samples with morphologic abnormalities in the marrow aspirate.

METHODS

Based on morphologic interpretation of bone marrow aspirate and flow cytometry, samples were triaged into four groups: (a) Samples with dysplasia or excess blasts had both NGS and karyotyping; (b) Samples without excess blasts or dysplasia had NGS only; (c) Repeat samples with previous NGS and/or CG studies were not retested; (d) Samples for suspected myeloma with less than 5% plasma cell had CG testing cancelled.

RESULTS

Seven hundred eleven adult bone marrow (BM) samples met the study criteria. The NGS first algorithm eliminated CG testing in 229/303 (75.6%) of patients, primarily by reducing repeat testing. Potential cost avoided was approximately $124 000 per annum. Hematologists overruled the triage comment in only 11/303 (3.6%) cases requesting CG testing for a specific indication.

CONCLUSIONS

Utilizing NGS as the primary genomic testing modality NGS was feasible and well accepted, reducing over three quarters of all CG requests and improving the financial case for adoption of NGS. Key factors for the success of this study were collaboration of clinical and genomic diagnostic teams in developing the algorithm, rapid turnaround time for BM interpretation for triage, and communication between laboratories.

The Interpretation of Sequence Variants in Myeloid Neoplasms

OBJECTIVES

To provide an overview of the challenges encountered during the interpretation of sequence variants detected by next-generation sequencing (NGS) in myeloid neoplasms, as well as the limitations of the technology with the goal of preventing the over- or undercalling of alterations that may have a significant effect on patient management.

METHODS

Review of the peer-reviewed literature on the interpretation, reporting, and technical challenges of NGS assays for myeloid neoplasms.

RESULTS

NGS has been integrated widely and rapidly into the standard evaluating of myeloid neoplasms. Review of the literature reveals that myeloid sequence variants are challenging to detect and interpret. Large insertions and guanine-cytosine-heavy areas prove technically challenging while frameshift and truncating alterations may be classified as variants of uncertain significance by tertiary analysis informatics pipelines due to their absence in the literature and databases.

CONCLUSIONS

The analysis and interpretation of NGS results in myeloid neoplasia are challenging due to the varied number of detectable gene alterations. Familiarity with the genomic landscape of myeloid malignancies and knowledge of the tools available for the interpretation of sequence variants are essential to facilitate translation into clinical and therapy decisions.

Analytical and Potential Clinical Performance of Oncomine Myeloid Research Assay for Myeloid Neoplasms

INTRODUCTION

Next-generation sequencing (NGS) panels have recently been introduced to efficiently detect genetic variations in hematologic malignancies.

OBJECTIVES

Our aim was to evaluate the performance of the commercialized Oncomine™ myeloid research assay (OMA) for myeloid neoplasms.

METHODS

Certified reference materials and clinical research samples were used, including 60 genomic DNA and 56 RNA samples. NGS was performed using OMA, which enables the interrogation of 40 target genes, 29 gene fusions, and five expression target genes with five expression control genes by the Ion S5 XL Sequencer. The analyzed data were compared with clinical data using karyotyping, reverse transcription polymerase chain reaction (PCR), fluorescence in situ hybridization, Sanger sequencing, customized NGS panel, and fragment analysis.

RESULTS

All targets of reference materials were detected except three (two ASXL1 and one CEBPA) mutations, which we had not expected OMA to detect. In clinical search samples, OMA satisfactorily identified DNA variants, including 90 single nucleotide variants (SNVs), 48 small insertions and deletions (indels), and eight FLT3 internal tandem duplications (ITDs) (Kappa agreement 0.938). The variant allele frequencies of SNVs and indels measured by OMA correlated well with clinical data, whereas those of FLT3-ITDs were significantly lower than with fragment analysis (P = 0.008). Together, OMA showed strong ability to identify RNA gene fusions (Kappa agreement 0.961), except one RUNX1-MECOM. The MECOM gene was highly expressed in all five samples with MECOM-associated rearrangements, including inv(3), t(3;3), and t(3;21).

CONCLUSION

OMA revealed excellent analytical and potential clinical performance and could be a good replacement for conventional molecular tests.

Determination of COL1A1-PDGFB breakpoints by next-generation sequencing in the molecular diagnosis of dermatofibrosarcoma protuberans

OBJECTIVE

In most cases, dermatofibrosarcoma protuberans (DFSP) is characterized by the chromosomal translocation t (17; 22) (q22; q13) that leads to a fusion of collagen type 1 alpha 1 (COL1A1) and platelet-derived growth factor beta chain (PDGFB). Recently, next-generation sequencing (NGS) has been reported to detect fusion transcripts in some malignancies. Therefore, the present study aimed to evaluate the utility of the targeted NGS in detecting the COL1A1-PDGFB fusion in patients with DFSP.

METHODS

We designed a targeted DNA capture panel to tile along the fusion regions, including exon, intron, and untranslated regions of the COL1A1 and PDGFB. A cohort of 18 DNA samples extracted from formalin-fixed, paraffin-embedded tissues was used to evaluate the targeted NGS. The results were compared with that of fluorescence in situ hybridization (FISH).

RESULTS

The COL1A1-PDGFB fusion was identified in 13 of 18 cases (72.2%) by targeted NGS assay. PDGFB breakpoints were constantly found in exon 2, while breakpoints in COL1A1 varied from exon 15 to 46. Of these 18 cases assayed by FISH, 12 (66.7%) exhibited COL1A1-PDGFB fusion signals. One case (P9), which was FISH-negative, was demonstrated with the fusion by targeted NGS and validated by PCR and Sanger sequencing. The targeted NGS results showed a high concordance with the results of the FISH assay (94.4%).

CONCLUSION

Our study reported a targeted NGS assay for detecting the breakpoints of the COL1A1-PDGFB fusion gene, which can be implemented in diagnosing patients with DFSP.

Validation, Implementation, and Clinical Impact of the Oncomine Myeloid Targeted-Amplicon DNA and RNA Ion Semiconductor Sequencing Assay

The identification of clinically significant genes recurrently mutated in myeloid malignancies necessitates expanding diagnostic testing with higher throughput, such as targeted next-generation sequencing. We present validation of the Thermo Fisher Oncomine Myeloid Next-Generation Sequencing Panel (OMP), targeting 40 genes and 29 fusion drivers recurrently mutated in myeloid malignancies. The study includes data from a sample exchange between two Canadian hospitals demonstrating high concordance for detection of DNA and RNA aberrations. Clinical validation demonstrates high accuracy, sensitivity, and specificity of the OMP, with a lower limit of detection of 5% for single-nucleotide variants and 10% for insertions/deletions. Prospective sequencing was performed for 187 samples from 168 unique patients presenting with suspected or confirmed myeloid malignancy and other hematological conditions to assess clinical impact of identifying variants. Of detected variants, 48% facilitated or clarified diagnoses, 29% affected prognoses, and 25% had the potential to influence clinical management. Of note, OMP was essential to identifying patients with premalignant clonal states likely contributing to cytopenias. We also found that the detection of even a single variant by the OMP assay, versus 0 variants, was predictive of overall survival, independent of age, sex, or diagnosis (P = 0.03). This study demonstrates that molecular profiling of myeloid malignancies with the OMP represents a promising strategy to advance molecular diagnostics.

Recurrent somatic mutations and low germline predisposition mutations in Korean ALL patients

In addition to somatic mutations, germline genetic predisposition to hematologic malignancies is currently emerging as an area attracting high research interest. In this study, we investigated genetic alterations in Korean acute lymphoblastic leukemia/lymphoma (ALL) patients using targeted gene panel sequencing. To this end, a gene panel consisting of 81 genes that are known to be associated with 23 predisposition syndromes was investigated. In addition to sequence variants, gene-level copy number variations (CNVs) were investigated as well. We identified 197 somatic sequence variants and 223 somatic CNVs. The IKZF1 alteration was found to have an adverse effect on overall survival (OS) and relapse-free survival (RFS) in childhood ALL. We found recurrent somatic alterations in Korean ALL patients similar to previous studies on both prevalence and prognostic impact. Six patients were found to be carriers of variants in six genes associated with primary immunodeficiency disorder (PID). Of the 81 genes associated with 23 predisposition syndromes, this study found only one predisposition germline mutation (TP53) (1.1%). Altogether, our study demonstrated a low probability of germline mutation predisposition to ALL in Korean ALL patients.

Improved Variant Detection in Clinical Myeloid NGS Testing by Supplementing a Commercial Myeloid NGS Assay with Custom or Extended Data Filtering and Accessory Fragment Analysis

BACKGROUND

Commercial myeloid next-generation sequencing (NGS) panels may facilitate uniform generation of raw data between laboratories. However, different strategies for data filtering and variant annotation may contribute to differences in variant detection and reporting. Here, we present how custom data filtering or the use of Oncomine extended data filtering improve detection of clinically relevant mutations with the Oncomine Myeloid Research Assay.

METHODS

The study included all patient samples (n = 264) analyzed during the first-year, single-site, clinical use of the Ion Torrent Oncomine Myeloid Research Assay. In data analysis, the default analysis filter was supplemented with our own data filtering algorithm in order to detect additional clinically relevant mutations. In addition, we developed a sensitive supplementary test for the ASXL1 c.1934dupG p.Gly646fs mutation by fragment analysis.

RESULTS

Using our custom filter chain, we found 96 different reportable variants that were not detected by the default filter chain. Twenty-six of these were classified as variants of strong or potential clinical significance (tier I/tier II variants), and the custom filtering discovered otherwise undetected tier I/tier II variants in 25 of 132 patients with clinically relevant mutations (19%). The remaining 70 variants not detected by the default filter chain were classified as variants of unknown significance. Among these were several unique variants with possible pathogenic potential judged by bioinformatic predictions. The recently launched Oncomine 5.14 extended filter algorithm detects most but not all of the tier I/tier II variants that were not detected by the default filter. The supplementary fragment analysis for the ASXL1 c.1934dupG p.Gly646fs confidently detected a variant allele frequency of down to 4.8% (SD 0.83%). The assay also detected the ASXL1 c.1900_1922del23 mutation.

CONCLUSION

Detection of clinically relevant variants with the Oncomine Myeloid Research NGS assay can be significantly improved by supplementing the default filter chain with custom data filtering or the recently launched Oncomine 5.14 extended filter algorithm. Our accessory fragment analysis facilitates easy testing for frequent ASXL1 mutations that are poorly or not covered by the NGS assay.

Gene Fusion Identification Using Anchor-Based Multiplex PCR and Next-Generation Sequencing

BACKGROUND

Methods for identifying gene fusion events, such as fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), and transcriptome analysis, are either single gene approaches or require bioinformatics expertise not generally available in clinical laboratories. We analytically validated a customized next-generation sequencing (NGS) panel targeting fusion events in 34 genes involving soft-tissue sarcomas.

METHODS

Specimens included 87 formalin-fixed paraffin-embedded (FFPE) tissues with known gene fusion status. Isolated total nucleic acid was used to identify fusion events at the RNA level. The potential fusions were targeted by gene-specific primers, followed by primer extension and nested PCR to enrich for fusion candidates with subsequent bioinformatics analysis.

RESULTS

The study generated results using the following quality metrics for fusion detection: (a) ≥100 ng total nucleic acid, (b) RNA average unique start sites per gene-specific primer control ≥10, (c) quantitative PCR assessing input RNA quality had a crossing point <30, (d) total RNA percentage ≥30%, and (e) total sequencing fragments ≥500 000.

CONCLUSIONS

The test validation study demonstrated analytical sensitivity of 98.7% and analytical specificity of 90.0%. The NGS-based panel generated highly concordant results compared to alternative testing methods.

The Importance of Targeted Next-Generation Sequencing Usage in Cytogenetically Normal Myeloid Malignancies

Advanced diagnostic methods give an advantage for the identification of abnormalities in myeloid malignancies. Various researchers have shown the potential importance of genetic tests before the disease's onset and in remission. Large testing panels prevent false-negative results in myeloid malignancies. However, the critical question is how the results of conventional cytogenetic and molecular cytogenetic techniques can be merged with NGS technologies. In this paper, we drew an algorithm for the evaluation of myeloid malignancies. To evaluate genetic abnormalities, we performed cytogenetics, molecular cytogenetics, and NGS testing in myeloid malignancies. In this study, we analyzed 100 patients admitted to the Medical Genetics Laboratory with different myeloid malignancies. We highlighted the possible diagnostic algorithm for cytogenetically normal cases. We applied NGS 141 gene panel for cytogenetically normal patients, and we detected two or more pathogenic variations in 61 out of 100 patients (61%). NGS's pathogenic variation detection rate varies in disease groups: they were present in 85% of A.M.L. and 23% of M.D.S. Here, we identified 24 novel variations out of total pathogenic variations in myeloid malignancies. A total of 18 novel variations were identified in A.M.L., and 6 novel variations were identified in M.D.S. Despite long turnaround times, conventional techniques are still a golden standard for myeloid malignancies but sometimes cryptic gene fusions or complex abnormalities cannot be easily identified by conventional techniques. In these conditions, advanced technologies like NGS are highly recommended.

Clinical and technical assessment of MedExome vs. NGS panels in patients with suspected genetic disorders in Southwestern Ontario

The adaptation of a broad genomic sequencing approach in the clinical setting has been accompanied by considerations regarding the clinical utility, technical performance, and diagnostic yield compared to targeted genetic approaches. We have developed MedExome, an integrated framework for sequencing, variant calling (SNVs, Indels, and CNVs), and clinical assessment of ~4600 medically relevant genes. We compared the technical performance of MedExome with the whole-exome and targeted gene-panel sequencing, assessed the reasons for discordance, and evaluated the added clinical yield of MedExome in a cohort of unresolved subjects suspected of genetic disease. Our analysis showed that despite a higher average read depth in panels (3058 vs. 855), MedExome yielded full coverage of the enriched regions (>20X) and 99% variant concordance rate with panels. The discordance rate was associated with low-complexity regions, high-GC content, and low allele fractions, observed in both platforms. MedExome yielded full sensitivity in detecting clinically actionable variants, and the assessment of 138 patients with suspected genetic conditions resulted in 76 clinical reports (31 full [22.1%], 3 partial, and 42 uncertain/possible molecular diagnoses). MedExome sequencing has comparable performance in variant detection to gene panels. Added diagnostic yield justifies expanded implementation of broad genomic approaches in unresolved patients; however, cost-benefit and health systems impact warrants assessment.

Clinical value of next-generation sequencing compared to cytogenetics in patients with suspected myelodysplastic syndrome

Next-generation sequencing (NGS) increasingly influences diagnosis, prognosis and management of myelodysplastic syndrome (MDS). In addition to marrow morphology and flow cytometry, our institution performs cytogenetics (CG) and NGS-based testing routinely in patients with suspected MDS. We evaluated the relative value of NGS in the assessment of patients with suspected MDS. We initially compared the diagnostic and prognostic information derived from CG and NGS in 134 patients. NGS enhanced the diagnostic yield compared to CG for clonal myeloid disorders (sensitivity 77% vs. 42·2%; specificity 90·2% vs. 78%; positive predictive value 92·8% vs. 76%; and negative predictive value 70·8% vs. 45·5%). The identification of poor prognosis mutations by NGS altered risk category in 27/39 (69·2%) patients with MDS with good/intermediate risk CG. Subsequently, we prospectively evaluated 70 patients with suspected MDS using an 'NGS-first approach' with CG restricted to samples with morphological abnormalities. We rarely identified mutations or CG abnormalities in patients without dysplastic features. NGS has a superior diagnostic performance compared to CG in patients with suspected MDS. We estimate that by using an 'NGS-first approach' we could reduce karyotyping by approximately 30%.

Feasibility of Combined Detection of Gene Mutations and Fusion Transcripts in Bone Marrow Trephines from Leukemic Neoplasms

Chromosomal translocations resulting in fusion genes represent important oncogenic drivers and potential therapeutic targets in rare leukemia subtypes. Formalin-fixed, paraffin-embedded trephines are frequently used in hematologic diagnostic tests and provide relevant access to leukemic cells for further studies, for example, phenotyping in bone marrow fibrosis. However, high-throughput molecular analysis of nucleic acids obtained from this material is challenging, especially the reliable detection of RNA transcripts. Sixty-three formalin-fixed, paraffin-embedded bone marrow trephines of patients with chronic eosinophilic leukemia, chronic myeloid leukemia, acute myeloid leukemia, and myeloproliferative neoplasms were analyzed for gene mutations and the presence of fusion transcripts with a commercial amplicon-based next-generation sequencing approach. Fusion transcripts relevant for diagnosis and therapy could be detected and validated (by RT-PCR) in 25 patients (39.7%). Retrospectively selected material, up to 10 years old, was used for this purpose, and only one sample failed in the RNA analysis (1.6%). This study concludes that amplicon-based fusion transcript detection in bone marrow trephines is feasible and that bone marrow trephines taken for histologic assessment can also be applied for high-throughput molecular analysis.