Next-generation sequencing-based detection of circulating tumour DNA After allogeneic stem cell transplantation for lymphoma

B-cell non-Hodgkin lymphomas

B-cell lymphomas occur with an incidence of 20 new cases per 100 000 people per year in high-income countries. They can affect any organ and are characterised by heterogeneous clinical presentations and courses, varying from asymptomatic, to indolent, to very aggressive cases. Since the topic of B-cell non-Hodgkin lymphomas was last reviewed in The Lancet in 2017, a deeper understanding of the biological background of this heterogeneous group of malignancies, the availability of new diagnostic methods, and the development and implementation of new targeted and immunotherapeutic approaches have improved our ability to treat patients. This Seminar provides an overview of the pathobiology, classification, and prognostication of B-cell non-Hodgkin lymphomas and summarises the current knowledge and standard of care regarding biology and clinical management of the most common subtypes of mature B-cell non-Hodgkin lymphomas. It also highlights new findings in deciphering the molecular background of disease development and the implementation of new therapeutic approaches, particularly those targeting the immune system.

Liquid biopsy in T-cell lymphoma: biomarker detection techniques and clinical application

T-cell lymphoma is a highly invasive tumor with significant heterogeneity. Invasive tissue biopsy is the gold standard for acquiring molecular data and categorizing lymphoma patients into genetic subtypes. However, surgical intervention is unfeasible for patients who are critically ill, have unresectable tumors, or demonstrate low compliance, making tissue biopsies inaccessible to these patients. A critical need for a minimally invasive approach in T-cell lymphoma is evident, particularly in the areas of early diagnosis, prognostic monitoring, treatment response, and drug resistance. Therefore, the clinical application of liquid biopsy techniques has gained significant attention in T-cell lymphoma. Moreover, liquid biopsy requires fewer samples, exhibits good reproducibility, and enables real-time monitoring at molecular levels, thereby facilitating personalized health care. In this review, we provide a comprehensive overview of the current liquid biopsy biomarkers used for T-cell lymphoma, focusing on circulating cell-free DNA (cfDNA), circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), Epstein-Barr virus (EBV) DNA, antibodies, and cytokines. Additionally, we discuss their clinical application, detection methodologies, ongoing clinical trials, and the challenges faced in the field of liquid biopsy.

Molecular Monitoring of Lymphomas

Molecular monitoring of tumor-derived alterations has an established role in the surveillance of leukemias, and emerging nucleic acid sequencing technologies are likely to similarly transform the clinical management of lymphomas. Lymphomas are well suited for molecular surveillance due to relatively high cell-free DNA and circulating tumor DNA concentrations, high somatic mutational burden, and the existence of stereotyped variants enabling focused interrogation of recurrently altered regions. Here, we review the clinical scenarios and key technologies applicable for the molecular monitoring of lymphomas, summarizing current evidence in the literature regarding molecular subtyping and classification, evaluation of treatment response, the surveillance of active cellular therapies, and emerging clinical trial strategies.

The evaluation of gene mutation profiles by next-generation sequencing in diffuse large B-cell lymphoma

OBJECTIVE

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. Although it is a clinically and biologically heterogeneous disease, it is usually treated with R-CHOP chemotherapy. Here, we aimed to investigate gene expression frequency with next-generation sequencing (NGS) and the relation of gene mutations with remission and relapse status in patients with DLBCLs.

MATERIALS AND METHODS

We investigated gene mutation profiles by NGS in patients with DLBCL-NOS and analyzed the correlation between gene mutations and response and relapse rates and other clinical indices.

RESULTS

Twenty-eight of forty patients were evaluated. The most commonly mutated genes were ANKRD, BRCA1, BRCA2, EZH2, KMTC2, MYC, MYD88, NF1, NOTCH1, PMS2, PTEN, and WRN. The relapse rate was found higher in DLBCL patients with ANKRD26, BRCA2, MYD88, and NOTCH1 mutations. Also, remission duration was found shorter in patients with ANKRD26, BRCA2, and MYD88 mutations.

CONCLUSIONS

Our study demonstrates that the presence of some genetic mutations is effective on prognosis in patients with DLBCL. NGS-based evaluation of DLBCL treatment can be used in the future.

An update on molecular features and therapeutic perspectives of pediatric classical Hodgkin Lymphoma. What the clinician needs to know?

Our understanding of Hodgkin lymphoma (HL) molecular biology has been radically transformed over recent years due to the advent and the spreading of the new generation sequencing approaches. These advances offer new insights about genetic predisposition to HL in children and are currently being translated into promising and more selective drugs (brentuximab and checkpoint inhibitors) offering the perspective to reduce treatment-related toxicity. Thus, as more than 90% of pediatric patients are cured after the first line treatment, a major emphasis is placed on survivorship by reducing treatment intensity, in particular, the use of radiotherapy and chemotherapy associated with long-term toxicities. The purposes of this review are to summarize the recent advances performed in the field of molecular biology of HL, in particular the promising development of liquid biopsies. We also provide an update review of immunodeficiencies associated to HL in children recently identified. Finally, we report the recent studies supporting the efficacy of new targeted therapeutics in adult and pediatric cHL (anti-CD30 and anti-PD1).

Monitoring of Measurable Residual Disease Using Circulating DNA after Allogeneic Hematopoietic Cell Transplantation

Simple Summary

The major cause of treatment failure after allogeneic stem cell transplantation (allo-HSCT) is due to relapse of the underlying disease. Novel methods and strategies are needed to detect early relapse after allo-HSCT. The present study reports the clinical utility of monitoring measurable residual disease (MRD) and mixed chimerism (MC) by droplet-digital PCR in circulating cell-free DNA (cfDNA) in 62 patients with myeloid malignancies undergoing allo-HSCT. MC in circulating cfDNA at an optimal threshold of 18% discriminated patients with hematological relapse from patients in complete remission after allo-HSCT. Most of the mutations identified using a targeted next-generation sequencing (NGS) panel were detected in cfDNA at relapse and were suitable for the monitoring of MRD. In several cases, mutations were detected earlier in cfDNA than in peripheral blood mononuclear cells. In conclusion, longitudinal analysis of cfDNA for MRD and MC can be used as a complementary tool for early detection of relapse in patients after allo-HSCT and could be used to guide clinical interventions.

Abstract

Relapse of the underlying disease is a frequent complication after allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this study, we describe the clinical utility of measurable residual disease (MRD) and mixed chimerism (MC) assessment in circulating cell-free DNA (cfDNA) analysis to detect earlier relapse in patients with hematological malignancies after allo-HSCT. A total of 326 plasma and peripheral blood mononuclear cell (PBMCs) samples obtained from 62 patients with myeloid malignancies were analyzed by droplet-digital PCR (median follow-up: 827 days). Comparison of MC in patients at relapse and in complete remission identified an optimal discriminating threshold of 18% of recipient-derived cfDNA. After performing a targeted next-generation sequencing (NGS) panel, 136 mutations in 58 patients were detected. In a total of 119 paired samples, the putative mutations were detected in both cfDNA and PBMCs in 73 samples (61.3%). In 45 samples (37.8%) they were detected only in cfDNA, and in only one patient (0.9%) were they detected solely in DNA from PBMCs. Hence, in 6 out of 23 patients (26%) with relapse after allo-HSCT, MRD positivity was detected earlier in cfDNA (mean 397 days) than in DNA derived from PBMCs (mean 451 days). In summary, monitoring of MRD and MC in cfDNA might be useful for earlier relapse detection in patients with myeloid malignancies after allo-HSCT.

The Minimal Residual Disease Using Liquid Biopsies in Hematological Malignancies

Simple Summary

Monitoring the response to treatment in hematologic malignancies is essential in defining the best way to optimize patient management. In general, achieving a deeper response has been shown to lead to a better prognosis, and the techniques used to study the minimal residual disease (MRD) are becoming more precise. The use of liquid biopsies, that is, analyzing the presence of alterations in nucleic acids, usually in peripheral blood or other biological fluids, is being studied and optimized with increasingly innovative molecular techniques, such as next-generation sequencing (NGS) in the monitoring of the MRD, avoiding, in many cases, more invasive tests in different hematological neoplasms. Currently, liquid biopsies are not standardized for the MRD monitoring, but there is increasing evidence of its correlation with other techniques to measure responses to treatments and patient outcomes.

Abstract

The study of cell-free DNA (cfDNA) and other peripheral blood components (known as “liquid biopsies”) is promising, and has been investigated especially in solid tumors. Nevertheless, it is increasingly showing a greater utility in the diagnosis, prognosis, and response to treatment of hematological malignancies; in the future, it could prevent invasive techniques, such as bone marrow (BM) biopsies. Most of the studies about this topic have focused on B-cell lymphoid malignancies; some of them have shown that cfDNA can be used as a novel way for the diagnosis and minimal residual monitoring of B-cell lymphomas, using techniques such as next-generation sequencing (NGS). In myelodysplastic syndromes, multiple myeloma, or chronic lymphocytic leukemia, liquid biopsies may allow for an interesting genomic representation of the tumor clones affecting different lesions (spatial heterogeneity). In acute leukemias, it can be helpful in the monitoring of the early treatment response and the prediction of treatment failure. In chronic lymphocytic leukemia, the evaluation of cfDNA permits the definition of clonal evolution and drug resistance in real time. However, there are limitations, such as the difficulty in obtaining sufficient circulating tumor DNA for achieving a high sensitivity to assess the minimal residual disease, or the lack of standardization of the method, and clinical studies, to confirm its prognostic impact. This review focuses on the clinical applications of cfDNA on the minimal residual disease in hematological malignancies.

Feasibility of Cell-Free DNA Collection and Clonal Immunoglobulin Sequencing in South African Patients With HIV-Associated Lymphoma

PURPOSE

Diagnosis of AIDS lymphoma in low-resource settings, like South Africa, is often delayed, leaving patients with limited treatment options. In tuberculosis (TB) endemic regions, overlapping signs and symptoms often lead to diagnostic delays. Assessment of plasma cell-free DNA (cfDNA) by next-generation sequencing (NGS) may expedite the diagnosis of lymphoma but requires high-quality cfDNA.

METHODS

People living with HIV with newly diagnosed aggressive B-cell lymphoma and those with newly diagnosed TB seeking care at Chris Hani Baragwanath Academic Hospital and its surrounding clinics, in Soweto, South Africa, were enrolled in this study. Each participant provided a whole blood specimen collected in cell-stabilizing tubes. Quantity and quality of plasma cfDNA were assessed. NGS of the immunoglobulin heavy chain was performed.

RESULTS

Nine HIV+ patients with untreated lymphoma and eight HIV+ patients with TB, but without lymphoma, were enrolled. All cfDNA quantity and quality metrics were similar between the two groups, except that cfDNA accounted for a larger fraction of recovered plasma DNA in patients with lymphoma. The concentration of cfDNA in plasma also trended higher in patients with lymphoma. NGS of immunoglobulin heavy chain showed robust amplification of DNA, with large amplicons (> 250 bp) being more readily detected in patients with lymphoma. Clonal sequences were detected in five of nine patients with lymphoma, and none of the patients with TB.

CONCLUSION

This proof-of-principle study demonstrates that whole blood collected for cfDNA in a low-resource setting is suitable for sophisticated sequencing analyses, including clonal immunoglobulin NGS. The detection of clonal sequences in more than half of patients with lymphoma shows promise as a diagnostic marker that may be explored in future studies.

Prognostic value of circulating tumor DNA in lymphoma: a meta-analysis

Circulating tumor DNA (ctDNA) can be used to evaluate the prognosis of lymphoma. However, there is no uniform consensus about the mechanistic role that ctDNA plays in the prognosis of lymphoma. This meta-analysis explores the prognostic value of ctDNA in lymphoma, especially in diffuse large B cell lymphoma (DLBCL). All relevant reports published as of May 14, 2020, were retrieved by searching electronic databases in Pubmed, Embase and Cochrane Library. The prognostic value of ctDNA was evaluated using meta-analysis. Revman 5.3 software was used for prognostic data extraction and analysis. Eight studies, including a total of 767 lymphoma patients, were enrolled in this meta-analysis. Five out of eight studies investigated the association between ctDNA levels and progression-free survival (PFS) in 501 lymphoma patients, indicating that high levels of ctDNA were significantly associated with poor PFS (HR 2.24, 95%CI: 1.63-3.08, P < 0.00001). We conducted a subgroup analysis of 379 patients with DLBCL across three of the studies and came to the same conclusion (HR 2.01, 95%CI: 1.42-2.85, P < 0.0001). Two studies with a total of 192 lymphoma patients described the association between ctDNA levels and event-free survival (EFS), showing that high levels of ctDNA were also associated with adverse EFS (HR 4.53, 95%CI: 1.79-11.47, P = 0.001). The remaining two studies analyzed the potential clinical value of ctDNA for predicting the overall survival time (OS) of DLBCL patients, demonstrating that high levels of ctDNA correlated with inferior OS (HR 3.09, 95%CI: 1.50-6.35, P = 0.002). Our meta-analysis showed that high levels of ctDNA were associated with poor prognosis in patients with lymphoma, especially DLBCL.

Stance of MRD in Non-Hodgkin's Lymphoma and its upsurge in the novel era of cell-free DNA

Cancer genomics has evolved over the years from understanding the pathogenesis of cancer to screening the future possibilities of cancer occurrence. Understanding the genetic profile of tumors holds a prognostic as well as a predictive value in this era of therapeutic surveillance, molecular remission, and precision medicine. Identifying molecular markers in tumors is the current standard of approach, and requires an efficient combination of an accessible sample type and a profoundly sensitive technique. Liquid biopsy or cell-free DNA has evolved as a novel sample type with promising results in recent years. Although cell-free DNA has significant role in various cancer types, this review focuses on its application in Non-Hodgkin's Lymphoma. Beginning with the current concept and clinical relevance of minimal residual disease in Non-Hodgkin's lymphoma, we discuss the literature on circulating DNA and its evolving application in the realm of cutting-edge technology.

2021 Update on Diffuse large B cell lymphoma: A review of current data and potential applications on risk stratification and management

Diffuse large B cell lymphoma (DLBCL), the most common type of Non-Hodgkin lymphoma (NHL), comprises a heterogeneous group of diseases with different biology, clinical presentations, and response to treatment. R-CHOP remains the mainstay of therapy and can achieve long-term disease control in nearly 90% of patients presenting with limited-stage and in up to 60% of those presenting with advanced stages. Advances on the understanding of the genetic landscape and molecular features of DLBCL have identified high-risk subsets with poor outcomes to chemo-immunotherapy that are actively being studied in clinical trials. Novel therapies could potentially improve outcomes for patients with high-risk disease. Studies evaluating risk-adapted therapy based on classification by cell of origin (COO) and molecular features are ongoing. Developments in the fields of immunotherapy, mostly with adoptive T-cell therapy, have significantly improved the outcomes of patients with relapsed refractory disease. In this review, we will summarize the recent data and discuss ongoing efforts to improve DLBCL treatment in the frontline and relapsed refractory settings.

Circulating tumor DNA by high-throughput sequencing of T cell receptor monitored treatment response and predicted treatment failure in T cell lymphomas

INTRODUCTION

Next-generation sequencing (NGS)-based circulating tumor DNA (ctDNA) detection is a promising monitoring tool for lymphoid malignancies. Studies for T cell lymphoma are limited.

METHODS

We explored whether this technology is applicable to T cell lymphoma with different subtypes and assessed its performance in clinical settings.

RESULTS

Thirty tumor and 74 blood samples were analyzed in our study. Malignant clone was identified in 23 of the 30 (76.7%) tumor samples through high-throughput sequencing (HTS) combined with PCR. We detected the same tumor clone in plasma in 18out of the 23 (78.3%) patients. Circulating tumor DNA fraction correlated with lactate dehydrogenase (LDH) (r = .52, P = .017), high level of ctDNA predicted treatment failure (P = .0003) and there was a trend patients with high ctDNA burden would have poorer PFS Furthermore, ctDNA changed in concordance with clinical outcome and was more sensitive than PET/CT. Also, recurrence of ctDNA was an important clue for relapse.

CONCLUSION

In conclusion, our study indicated that ctDNA monitoring was suitable for T cell lymphoma. High level of pretreatment ctDNA was a poor prognosis factor and changes of ctDNA correlated well with clinical courses and was sensitive to find early relapse.

Clinical Value of ctDNA in Hematological Malignancies (Lymphomas, Multiple Myeloma, Myelodysplastic Syndrome, and Leukemia): A Meta-Analysis

Background: Circulating tumor DNA (ctDNA) has offered a minimally invasive approach for the detection and measurement of cancer. However, its diagnostic and prognostic value in hematological malignancies remains unclear.

Materials and methods: Pubmed, Embase, and Cochrane Library were searched for relating literature. Diagnostic accuracy variables and disease progression prediction data were pooled by the Meta-Disc version 1.4 software. Review Manager version 5.4 software was applied for prognostic data analysis.

Results: A total of 11 studies met our inclusion criteria. In terms of diagnosis, the pooled sensitivity and specificity were 0.51 (95% confidence intervals (CI) 0.38–0.64) and 0.96 (95% CI 0.88–1.00), respectively. The AUSROC (area under the SROC) curve was 0.89 (95%CI 0.75–1.03). When it comes to the prediction of disease progression, the overall sensitivity and specificity was 0.83 (95% CI 0.67–0.94) and 0.98 (95% CI 0.93–1.00), respectively. Moreover, a significant association also existed between the presence of ctDNA and worse progression-free survival (HR 2.63, 95% CI 1.27–5.43, p = 0.009), as well as overall survival (HR 2.92, 95% CI 1.53–5.57, p = 0.001).

Conclusions: The use of ctDNA in clinical practice for hematological malignancies is promising, as it may not only contribute to diagnosis, but could also predict the prognosis of patients so as to guide treatment. In the future, more studies are needed to realize the standardization of sequencing techniques and improve the detection sensitivity of exploration methods.

Role of cell-free DNA in haematological malignancies

Cell-free DNA (cfDNA) consists of fragments of double stranded DNA that are found in the circulation. They are released from the apoptosis of both normal haemopoietic cells and malignant cells. The use of cfDNA from easily accessible peripheral blood samples has created a new strategy in studying molecular genomics in haematological malignancies. Its use in diagnosis, prognosis and monitoring potentially precludes the need for repeated tissue samples, i.e., bone marrow biopsy or primary tissue biopsy. It also potentially provides a more comprehensive analysis of the disease as cfDNA are released from tumours from multiple sites of the body. While cfDNA research is still in its infancy, given its potential and the expansion in next generation sequencing (NGS) it has attracted a lot of attention in recent years. This review will focus on acute leukaemia, multiple myeloma and lymphoma and the potential diagnostic and prognostic implications of cfDNA, its role in response assessment and in detection of disease relapse.

Prognosis and risk stratification of peripheral T-cell lymphomas

Peripheral T-cell lymphomas represent a rare heterogeneous group of non-Hodgkin lymphomas with generally worse outcomes with standard chemotherapy compared to B-cell lymphomas. Clinical risk prediction tools at baseline have been shown to be prognostic but generally do not impact clinical decision making. However, improving understanding of the prognostic implications of histology and its molecular underpinnings as well as strategies surrounding the use of CD30 as a predictive biomarker for brentuximab vedotin have led to better understanding of how to risk stratify patients. Baseline, interim, and end of treatment PET/CT as evaluated by the Lugano criteria as well as by baseline metabolic tumor volume have also been shown to be prognostic. The role of minimal residual disease tools such as cell free DNA and T-cell gene receptor sequencing remain active areas of investigation in hopes to develop predictive biomarkers in these rare diseases. This review focuses on strategies used to prognosticate in more common forms of peripheral T-cell lymphoma as well as in extranodal NK/T-cell lymphoma.

Noninvasive Monitoring of Mantle Cell Lymphoma by Immunoglobulin Gene Next-Generation Sequencing in a Phase 2 Study of Sequential Chemoradioimmunotherapy Followed by Autologous Stem-Cell Rescue

Limited information exists in mantle cell lymphoma (MCL) on the performance of next-generation sequencing–based assay of immunoglobulin gene rearrangements for minimal residual disease (MRD) assessment. Posttreatment peripheral blood samples were collected from 16 MCL patients and analyzed with the Adaptive Biotechnologies MRD assay, which identified early molecular relapse. We observed more sensitivity in the cellular versus acellular compartment.

Measurable residual disease in the treatment of chronic lymphocytic leukemia

Treatment outcomes of chronic lymphocytic leukemia (CLL) have improved since chemoimmunotherapy and novel drugs became available for CLL treatment; therefore, more sensitive methods to evaluate residual CLL cells in patients are required. Measurable residual disease (MRD) has been assessed in several clinical trials on CLL using flow cytometry, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers, and high-throughput sequencing. MRD assessment is useful to predict the treatment outcomes in the context of chemotherapy and treatment with novel drugs such as venetoclax. In this review, we discuss major techniques for MRD assessment, data from relevant clinical trials, and the future of MRD assessment in CLL treatment.

Ofatumumab, Etoposide, and Cytarabine Intensive Mobilization Regimen in Patients with High-risk Relapsed/Refractory Diffuse Large B-Cell Lymphoma Undergoing Autologous Stem Cell Transplantation

BACKGROUND

More than one-half of high-risk patients with relapsed/refractory (rr) diffuse large B-cell lymphoma (DLBCL) relapse after autologous hematopoietic cell transplantation (auto-HCT). In this phase II study, we investigate the long-term outcomes of high-risk patients with rrDLBCL receiving intensive consolidation therapy (ICT) with OVA (ofatumumab, etoposide, and high-dose cytarabine) prior to auto-HCT.

PATIENTS AND METHODS

The primary endpoints were the ability of OVA to mobilize peripheral stem cells and the 2-year progression-free survival (PFS) rate following OVA. Secondary endpoints included safety, 2-year overall survival (OS), impact of cell of origin (COO), and the prognostic utility of next-generation sequencing minimal residual disease (MRD) testing. We simultaneously retrospectively assessed the outcomes of DLBCL patients who underwent ICT with a similar regimen at our institution.

RESULTS

Twenty-seven patients received salvage chemotherapy, with a response rate of 25% in patients with germinal center B-cell (GCB)-DLBCL versus 92% in patients with non-GCB-DLBCL (P = .003). Nineteen responding patients underwent ICT with OVA (100% successful stem cell mobilization). The 2-year PFS and OS rate was 47% and 59%, respectively, with no difference based on COO. Similar findings were observed when the study and retrospective cohorts were combined. Neutropenia was the most common toxicity (47%). MRD-negative patients at the completion of salvage had a median OS of not reached versus 3.5 months in MRD-positive patients (P = .02).

CONCLUSIONS

OVA followed by auto-HCT is effective and safe for high-risk rrDLBCL. Patients with GCB-DLBCL had a lower response to salvage chemotherapy, but no difference in outcomes based on COO was seen after auto-HCT. MRD testing in the relapsed setting was predictive of long-term survival.

Advances in the assessment of minimal residual disease in mantle cell lymphoma

The clinical impact of minimal residual disease detection at early time points or during follow-ups has been shown to accurately predict relapses among patients with lymphomas, mainly in follicular and diffuse large B cell lymphoma. The field of minimal residual disease testing in mantle cell lymphoma is still evolving but has great impact in determining the prognosis. Flow cytometry and polymerase chain reaction-based testing are most commonly used methods in practice; however, these methods are not sensitive enough to detect the dynamic changes that underline lymphoma progression. Newer methods using next-generation sequencing, such as ClonoSeq, are being incorporated in clinical trials. Other techniques under evolution include CAPP-seq and anchored multiplex polymerase chain reaction-based methods. This review article aims to provide a comprehensive update on the status of minimal residual disease detection and its prognostic effect in mantle cell patients. The role of circulating tumor DNA-based minimal residual disease detection in lymphomas is also discussed.

The future of cell-free DNA testing to guide therapeutic decisions in B-cell lymphomas

PURPOSE OF REVIEW

Tissue biopsy is the current gold standard technique for diagnosis and molecular profiling of lymphomas, but it carries several disadvantages in terms of procedural risks (infectious and haemorrhagic complications, anaesthesiologic risks) and analytic aspects (heterogeneity of tumors, low representation of tumor cells in the tissue). Noninvasive genotyping of B-cell lymphomas through circulating tumor DNA (ctDNA) is emerging as a practical tool to monitor the genetics and course of the disease from diagnosis to eventual relapse.This review will explore recent advances in the field of liquid biopsy in lymphomas, highlighting their clinical implications.

RECENT FINDINGS

ctDNA has been recently proposed an alternative source of tumor DNA for genotyping purposes, especially for those samples having low tumor representation or when longitudinal genetic monitoring is limited by the inaccessibility of relapsed tumor tissues. Also, ctDNA has been recently proposed radiation-free tool for the early identification of chemorefractory lymphoma patients.

SUMMARY

The detection of ctDNA circulating in the bloodstream of lymphoma patients can inform about the genetics of the disease at diagnosis identifying druggable alterations, detect the onset of mutation of resistance during treatment, anticipate about relapse earlier than standard methods [e.g. PET associated with computed tomography (PET/CT)] during follow-up.

Targeted next-generation sequencing of circulating cell-free DNA vs bone marrow in patients with acute myeloid leukemia

Circulating cell-free DNA (ccfDNA) allows for noninvasive peripheral blood sampling of cancer-associated mutations and has established clinical utility in several solid tumors. We performed targeted next-generation sequencing of ccfDNA and bone marrow at the time of diagnosis and after achieving remission in 22 patients with acute myeloid leukemia (AML). Among 28 genes sequenced by both platforms, a total of 39 unique somatic mutations were detected. Five mutations (13%) were detected only in ccfDNA, and 15 (38%) were detected only in bone marrow. Among the 19 mutations detected in both sources, the concordance of variant allelic frequency (VAF) assessment by both methods was high (R2 = 0.849). Mutations detected in only 1 source generally had lower VAF than those detected in both sources, suggesting that either method may miss small subclonal populations. In 3 patients, sequencing of ccfDNA detected new or persistent leukemia-associated mutations during remission that appeared to herald overt relapse. Overall, this study demonstrates that sequencing of ccfDNA in patients with AML can identify clinically relevant mutations not detected in the bone marrow and may play a role in the assessment of measurable residual disease. However, mutations were missed by both ccfDNA and bone marrow analyses, particularly when the VAF was <10%, suggesting that ccfDNA and bone marrow may be complementary in the assessment and monitoring of patients with AML.

The Impact of Pre-transplant Cell-free DNA Levels on Leukemia Relapse and Transplant-related Complications in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Background:

Cell-free DNA, which may be considered as “liquid” biopsy, may serve as a diagnostic and prognostic marker not only in hematological malignancies but in solid tumors as well.

Aims:

To investigate the prognostic role of pre-transplant cell-free DNA levels in allogeneic hematopoietic stem cell transplant recipients.

Study Design:

Retrospective cohort study.

Methods:

A total of 177 allogeneic hematopoietic stem cell transplant recipients [median age: 36 (16-66) years; male/female: 111/66] with an initial diagnosis of acute leukemia were included in the study. Cell-free DNA was extracted from pre-transplant serum samples by using the MagNA Pure Compact Nucleic Acid Isolation Kit I with the MagNA Pure Compact instrument (Roche Diagnostics, Penzberg, Germany).

Results:

A positive correlation was demonstrated between cell-free DNA and age (p=0.018; r=0.177). Pre-transplant cell-free DNA levels were lower in bcr-abl (+) patients (p=0.001), while an adverse correlation was indicated between cell-free DNA and bcr-abl levels (p=0.001; r=−0.531). Acute lymphoblastic leukemia patients with bcr-abl positivity (p=0.001) or abnormal cytogenetics (p=0.038) represented significantly lower pre-transplant cell-free DNA levels. Cell-free DNA levels were lower in patients who developed sinusoidal obstruction syndrome (p=0.035). In terms of long-term complications, acute myeloid leukemia patients who experienced post-transplant relapse had significantly lower pre-transplant cell-free DNA levels (p=0.024). Overall survival was not statistically different between high- and low- cell-free DNA groups (45.2% vs 22.5; p=0.821).

Conclusion:

In general, low serum levels of pre-transplant cell-free DNA seem to be associated with transplant-related morbidities and may be considered an adverse prognostic factor for allogeneic hematopoietic stem cell transplant recipients.

Minimal residual disease undetectable by next-generation sequencing predicts improved outcome in CLL after chemoimmunotherapy

Patients with chronic lymphocytic leukemia (CLL) who achieve blood or bone marrow (BM) undetectable minimal residual disease (U-MRD) status after first-line fludarabine, cyclophosphamide, and rituximab (FCR) have prolonged progression-free survival (PFS), when assessed by an assay with sensitivity 10-4 (MRD4). Despite reaching U-MRD4, many patients, especially those with unmutated IGHV, subsequently relapse, suggesting residual disease <10-4 threshold and the need for more sensitive MRD evaluation. MRD evaluation by next-generation sequencing (NGS) has a sensitivity of 10-6 (MRD6). To better assess the depth of remission following first-line FCR treatment, we used NGS (Adaptive Biotechnologies Corporation) to assess MRD in 62 patients, all of whom had BM U-MRD by multicolor flow cytometry (sensitivity 10-4) at end-of-FCR treatment. Samples from these patients included 57 BM samples, 29 peripheral blood mononuclear cell (PBMC) samples, and 32 plasma samples. Only 27.4% of the 62 patients had U-MRD by NGS. Rate of U-MRD by NGS was lowest in BM (25%), compared with PBMC (55%) or plasma (75%). No patient with U-MRD by NGS in BM or PBMC was MRD+ in plasma. Patients with mutated IGHV were more likely to have U-MRD by NGS at the end of treatment (EOT; 41% vs 13%, P = .02) than those with unmutated IGHV. Median follow-up was 81.6 months. Patients with U-MRD at EOT had superior PFS vs MRD+ patients, regardless of sample type assessed (BM, P = .02, median not reached [NR] vs 67 months; PBMC, P = .02, median NR vs 74 months). More sensitive MRD6 testing increases prognostic discrimination over MRD4 testing.

The role of cell free DNA and liquid biopsies in haematological conditions

Cell free nucleic acids (CFNAs) are nucleic acids released from cells that circulate within bodily fluids. Recent advances in molecular techniques have led the ability to interrogate CFNAs in a clinically meaningful way, for example the identification and assessment of foetal CFNAs in maternal blood, allowing minimally invasive testing for foetal genetic abnormalities. The majority of CFNAs arise from haemopoietic cells, making it a particularly rich source of genetic information in haematological conditions. Furthermore, the innate genetic heterogeneity of haematological malignancies, as epitomised by multiple myeloma, lend itself well to “liquid biopsies”. This approach promises to provide a more wholistic assessment of whole disease genetics, especially when contrasted against the current gold-standard of single site tissue biopsies. This review briefly summarises the definitions and physiology of CFNAs, both cell free DNA (cfDNA) and extracellular RNA (exRNA), before exploring the literature surrounding the current and future roles of cfDNA in the haematological malignancies and patient care.

Molecular Complexity of Diffuse Large B-Cell Lymphoma: Can It Be a Roadmap for Precision Medicine?

Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma; it features extreme molecular heterogeneity regardless of the classical cell-of-origin (COO) classification. Despite this, the standard therapeutic approach is still immunochemotherapy (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone-R-CHOP), which allows a 60% overall survival (OS) rate, but up to 40% of patients experience relapse or refractory (R/R) disease. With the purpose of searching for new clinical parameters and biomarkers helping to make a better DLBCL patient characterization and stratification, in the last years a series of large discovery genomic and transcriptomic studies has been conducted, generating a wealth of information that needs to be put in order. We reviewed these researches, trying ultimately to understand if there are bases offering a roadmap toward personalized and precision medicine also for DLBCL.

Minimal Residual Disease in Chronic Lymphocytic Leukemia: A New Goal?

In chronic lymphocytic leukemia (CLL), there is a growing interest for minimal residual disease (MRD) monitoring, due to the availability of drug combinations capable of unprecedented complete clinical responses. The standardized and most commonly applied methods to assess MRD in CLL are based on flow cytometry (FCM) and, to a lesser extent, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers of immunoglobulin heavy chain genes (IgH). Promising results are being obtained using droplet digital PCR (ddPCR) and next generation sequencing (NGS)-based approaches, with some advantages and a potential higher sensitivity compared to the standardized methodologies. Plasma cell-free DNA can also be explored as a more precise measure of residual disease from all different compartments, including the lymph nodes. From a clinical point of view, CLL MRD quantification has proven an independent prognostic marker of progression-free survival (PFS) and overall survival (OS) after chemoimmunotherapy as well as after allogeneic transplantation. In the era of mechanism-driven drugs, the paradigms of CLL treatment are being revolutionized, challenging the use of chemoimmunotherapy even in first-line. The continuous administration of ibrutinib single agent has led to prolonged PFS and OS in relapsed/refractory and treatment naïve CLL, including those with TP53 deletion/mutation or unmutated IGHV genes, though the clinical responses are rarely complete. More recently, chemo-free combinations of venetoclax+rituximab, venetoclax+obinutuzumab or ibrutinib+venetoclax have been shown capable of inducing undetectable MRD in the bone marrow, opening the way to protocols exploring a MRD-based duration of treatment, aiming at disease eradication. Thus, beside a durable disease control desirable particularly for older patients and/or for those with comorbidities, a MRD-negative complete remission is becoming a realistic prospect for CLL patients in an attempt to obtain a long-lasting eradication and possibly cure of the disease. Here we discuss the standardized and innovative technical approaches for MRD detection in CLL, the clinical impact of MRD monitoring in chemoimmunotherapy and chemo-free trials and the future clinical implications of MRD monitoring in CLL patients outside of clinical trials.

Updates on Circulating Tumor DNA Assessment in Lymphoma

PURPOSE OF REVIEW

The use of circulating tumor DNA (ctDNA) for the purposes of diagnosis, prognosis, assessment of treatment response, and monitoring for relapse is a new and developing field in lymphoma. This review aims to summarize many of the most recent advances in ctDNA applications.

RECENT FINDINGS

Recent studies have demonstrated the use of ctDNA assessment across many lymphoma subtypes including diffuse large B-cell lymphoma, follicular lymphoma, Hodgkin lymphoma, and T-cell lymphoma. In addition, many novel applications of ctDNA assessment have been described such as the development of new prognostic models, investigation of clonal evolution and heterogeneity, early assessment of treatment response, and prediction of response to targeted therapy as a form of personalized medicine. The use of ctDNA has been shown to be feasible across many lymphoma subtypes and has shown significant promise for several new applications. Additional studies will be needed to validate these findings prior to routine use in clinical practice.

Mutation Profiling of Malignant Lymphoma by Next-Generation Sequencing of Circulating Cell-Free DNA

Background: Malignant lymphomas are a group of distinct lymphoid neoplasms, exhibiting marked diversity in biological behaviors and clinical outcomes. Liquid biopsy, such as circulating cell-free DNA (cfDNA), has recently been attempted to be used for mutation profiling of lymphomas using next-generation sequencing (NGS). However, only limited data about cfDNA are restricted in Hodgkin's lymphoma and B cell lymphoma, and there is no report in the T cell lymphoma so far. Patient and Methods: Medical records of a total of 50 lymphoma patients were retrospectively reviewed, and cfDNA samples were analyzed by capture-based NGS targeting 390 lymphoma- and cancer- relevant genes. We sought to explore the clinical utility of cfDNA in establishing the mutation profiles of different lymphoma subtypes and analyze the correlation between cfDNA concentration and other clinical indices such as serum LDH and IPI. Results: Somatic alterations were identified in cfDNA samples with a median of 64 variants per sample. The concentration of cfDNA in the plasma was found to be significantly correlated with the clinical indices in diffuse large B cell lymphoma (DLBCL). The genetic heterogeneity of different lymphoma subtypes was clearly observed in cfDNAs from germinal center B-cell (GCB) DLBCL, non-GCB DLBCL and natural killer/T-cell lymphoma (NKTCL), confirming that distinct molecular mechanisms are involved in the pathogenesis of different lymphomas. Conclusion: Our findings demonstrate that NGS-based cfDNA mutation profiling reveals genetic heterogeneity across lymphoma subtypes, with potential implications for the discovery of therapeutic targets, the exploration of genome evolution and the development of risk-adapted treatment.

Circulating tumor DNA: clinical roles in diffuse large B cell lymphoma

Diffuse large B cell lymphoma (DLBCL), the most common non-Hodgkin lymphoma (NHL), is a clinically and molecularly heterogeneous malignant lymphoproliferative disease. In the era of personalized medicine, genetic information is critical to early diagnosis, aiding risk stratification, directing therapeutic option, and monitoring disease relapse. However, lacking a circulating disease with most DLBCL cases hampers the acquisition of tumor genomic landscapes and disease dynamics. Circulating tumor DNA (ctDNA) is a novel noninvasive, real-time, and tumor-specific biomarker, reliably reflecting the comprehensive tumor genetic profiles, thus holds great promise in individualized medicine, including precise diagnosis and prognosis, response monitoring, and relapse detection of DLBCL. Here, we reviewed the recent advances of ctDNA in DLBCL and discussed its clinical values at different time points during the disease courses by comparing with the current routine methods in clinical practice. Collectively, we anticipated that ctDNA will ultimately be integrated into the management of DLBCL to facilitate precision medicine.

New Molecular Technologies for Minimal Residual Disease Evaluation in B-Cell Lymphoid Malignancies

The clearance of malignant clonal cells significantly correlates with clinical outcomes in many hematologic malignancies. Accurate and high throughput tools for minimal residual disease (MRD) detection are needed to overcome some drawbacks of standard molecular techniques; such novel tools have allowed for higher sensitivity analyses and more precise stratification of patients, based on molecular response to therapy. In this review, we depict the recently introduced digital PCR and next-generation sequencing technologies, describing their current application for MRD monitoring in lymphoproliferative disorders. Moreover, we illustrate the feasibility of these new technologies to test less invasive and more patient-friendly tissues sources, such as "liquid biopsy".

Noninvasive Molecular Monitoring in Multiple Myeloma Patients Using Cell-Free Tumor DNA: A Pilot Study

Novel treatments for multiple myeloma (MM) have increased rates of complete response, raising interest in more accurate methods to evaluate residual disease. Cell-free tumor DNA (cfDNA) analysis may represent a minimally invasive approach complementary to multiparameter flow cytometry (MFC) and molecular methods on bone marrow aspirates. A sequencing approach using the Ion Torrent Personal Genome Machine was applied to identify clonal IGH gene rearrangements in tumor plasma cells (PCs) and in serial plasma samples of 25 patients with MM receiving second-line therapy. The same clonal IGH rearrangement identified in tumor PCs was detected in paired plasma samples, and levels of IGH cfDNA correlated with outcome and mirrored tumor dynamics evaluated using conventional laboratory parameters. In addition, IGH cfDNA levels reflected the number of PCs enumerated by MFC immunophenotyping even in the complete response context. Patients determined by MFC to be free of minimal residual disease were characterized by low frequencies of tumor clonotypes in cfDNA and longer survival. This pilot study supports the clinical applicability of the noninvasive monitoring of tumor levels in plasma samples of patients with MM by IGH sequencing.

Methods and role of minimal residual disease after stem cell transplantation

Relapse is the major cause of treatment failure after stem cell transplantation. Despite the fact that relapses occurred even if transplantation was performed in complete remission, it is obvious that minimal residual disease is present though not morphologically evident. Since adaptive immunotherapy by donor lymphocyte infusion or other novel cell therapies as well as less toxic drugs, which can be used after transplantation, the detection of minimal residual disease (MRD) has become a clinical important variable for outcome. Besides the increasing options to treat MRD, the most advanced technologies currently allow to detect residual malignant cells with a sensitivity of 10^-5 to 10^-6.Under the patronage of the European Society for Blood and Marrow Transplantation (EBMT) and the American Society for Blood and Marrow Transplantation (ASBMT) the 3rd workshop was held on 4/5 November 2016 in Hamburg/Germany, with the aim to present an up-to-date status of epidemiology and biology of relapse and to summarize the currently available options to prevent and treat post-transplant relapse. Here the current methods and role of minimal residual disease for myeloid and lymphoid malignancies are summarized.

Circulating tumor DNA dynamically predicts response and/or relapse in patients with hematological malignancies

A growing body of evidence suggests that tumor-derived fragmentary DNA, known as circulating tumor DNA (ctDNA), has the potential to serve as a non-invasive biomarker for disease monitoring. However, in the setting of hematological malignancy, few published studies support the utility of ctDNA. We retrospectively investigated ctDNA levels of 17 patients with various hematological malignancies who had achieved remission after first-line therapy. We identified somatic driver mutations by next-generation sequencing, and designed droplet digital PCR assays for each mutation to measure ctDNA. Variant allele frequencies of ctDNA changed in association with clinical response in all patients. Eight patients clinically relapsed after a median of 297 days post-first-line therapy (termed, "relapsed group"); the remaining nine patients remained disease-free for a median of 332 days (termed, "remission group"). Among patients in the relapsed group, ctDNA levels increased more than twofold at paired serial time points. In marked contrast, ctDNA levels of all patients in the remission group remained undetectable or stable during clinical remission. Notably, ctDNA-based molecular relapse demonstrated a median 30-day lead time over clinical relapse. In summary, ctDNA monitoring may help identify hematologic cancer patients at risk for relapse in advance of established clinical parameters.

The value of cell-free DNA for molecular pathology

Over the past decade, advances in molecular biology and genomics techniques have revolutionized the diagnosis and treatment of cancer. The technological advances in tissue profiling have also been applied to the study of cell-free nucleic acids, an area of increasing interest for molecular pathology. Cell-free nucleic acids are released from tumour cells into the surrounding body fluids and can be assayed non-invasively. The repertoire of genomic alterations in circulating tumour DNA (ctDNA) is reflective of both primary tumours and distant metastatic sites, and ctDNA can be sampled multiple times, thereby overcoming the limitations of the analysis of single biopsies. Furthermore, ctDNA can be sampled regularly to monitor response to treatment, to define the evolution of the tumour genome, and to assess the acquisition of resistance and minimal residual disease. Recently, clinical ctDNA assays have been approved for guidance of therapy, which is an exciting first step in translating cell-free nucleic acid research tests into clinical use for oncology. In this review, we discuss the advantages of cell-free nucleic acids as analytes in different body fluids, including blood plasma, urine, and cerebrospinal fluid, and their clinical applications in solid tumours and haematological malignancies. We will also discuss practical considerations for clinical deployment, such as preanalytical factors and regulatory requirements. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Circulating tumor DNA reveals genetics, clonal evolution, and residual disease in classical Hodgkin lymphoma

The rarity of neoplastic cells in the biopsy imposes major technical hurdles that have so far limited genomic studies in classical Hodgkin lymphoma (cHL). By using a highly sensitive and robust deep next-generation sequencing approach for circulating tumor DNA (ctDNA), we aimed to identify the genetics of cHL in different clinical phases, as well as its modifications on treatment. The analysis was based on specimens collected from 80 newly diagnosed and 32 refractory patients with cHL, including longitudinal samples collected under ABVD (adriamycin, bleomycin, vinblastine, dacarbazine) chemotherapy and longitudinal samples from relapsing patients treated with chemotherapy and immunotherapy. ctDNA mirrored Hodgkin and Reed-Sternberg cell genetics, thus establishing ctDNA as an easily accessible source of tumor DNA for cHL genotyping. By identifying STAT6 as the most frequently mutated gene in ∼40% of cases, we refined the current knowledge of cHL genetics. Longitudinal ctDNA profiling identified treatment-dependent patterns of clonal evolution in patients relapsing after chemotherapy and patients maintained in partial remission under immunotherapy. By measuring ctDNA changes during therapy, we propose ctDNA as a radiation-free tool to track residual disease that may integrate positron emission tomography imaging for the early identification of chemorefractory patients with cHL. Collectively, our results provide the proof of concept that ctDNA may serve as a novel precision medicine biomarker in cHL.

Minimal Residual Disease Assessment in Lymphoma: Methods and Applications

Standard methods for disease response assessment in patients with lymphoma, including positron emission tomography and computed tomography scans, are imperfect. In other hematologic malignancies, particularly leukemias, the ability to detect minimal residual disease (MRD) is increasingly influencing treatment paradigms. However, in many subtypes of lymphoma, the application of MRD assessment techniques, like flow cytometry or polymerase chain reaction-based methods, has been challenging because of the absence of readily detected circulating disease or canonic chromosomal translocations. Newer MRD detection methods that use next-generation sequencing have yielded promising results in a number of lymphoma subtypes, fueling the hope that MRD detection may soon be applicable in clinical practice for most patients with lymphoma. MRD assessment can provide real-time information about tumor burden and response to therapy, noninvasive genomic profiling, and monitoring of clonal dynamics, allowing for many possible applications that could significantly affect the care of patients with lymphoma. Further validation of MRD assessment methods, including the incorporation of MRD assessment into clinical trials in patients with lymphoma, will be critical to determine how best to deploy MRD testing in routine practice and whether MRD assessment can ultimately bring us closer to the goal of personalized lymphoma care. In this review article, we describe the methods available for detecting MRD in patients with lymphoma and their relative advantages and disadvantages. We discuss preliminary results supporting the potential applications for MRD testing in the care of patients with lymphoma and strategies for including MRD assessment in lymphoma clinical trials.

Diffuse large B-cell lymphoma

Diffuse large B cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma worldwide, representing approximately 30-40% of all cases in different geographic regions. Patients most often present with a rapidly growing tumour mass in single or multiple, nodal or extranodal sites. The most common type of DLBCL, designated as not otherwise specified, represents 80-85% of all cases and is the focus of this review. There are also rare types of lymphoma composed of large B-cells, in aggregate about 15-20% of all neoplasms that are sufficiently distinctive to recognise separately. DLBCL not otherwise specified (referred to henceforth as DLBCL) is a heterogeneous entity in terms of clinical presentation, genetic findings, response to therapy, and prognosis. A major advance was the application of gene expression profiling (GEP) to the study of DLBCL which further clarified this heterogeneity and provided a rationale for subdividing cases into groups. The most popular system divides cases of DLBCL according to cell-of-origin into germinal centre B-cell like (GCB) and activated B-cell like (ABC) subtypes, with about 10-15% of cases being unclassifiable. Patients with the GCB subtype usually have better prognosis than patients with the ABC subtype. Although cell-of-origin is useful for predicting outcome, the GCB and ABC subtypes remain heterogeneous, with better and worse prognostic subsets within each group. Next generation sequencing (NGS) analysis of DLBCL has facilitated global identification of numerous and diverse genetic abnormalities in these neoplasms and has shown that GCB and ABC tumours have different mutation profiles. Although the therapy of patients with DLBCL is an active area of research, the current 5-year overall survival rate is 60-70% using standard-of-care frontline therapy. A precision medicine approach for the design of new therapies based on molecular findings in DLBCL is likely the best path forward. As pathologists, our role has expanded beyond diagnosis. We must perform a complete work-up of DLBCL cases. In addition to our traditional role in establishing the diagnosis, we need to analyse markers that provide information regarding prognosis and potential therapeutic targets. We also must ensure that adequate tissue is triaged for molecular studies which are essential for designing therapy regimens, particularly in the setting of disease relapse.

Minimal residual disease in non-Hodgkin lymphoma - current applications and future directions

Non-Hodgkin Lymphomas (NHLs) are a heterogeneous group of tumours with distinct treatment paradigms, but in all cases the goal of treatment is to maximize quality and duration of remission while minimizing therapy-related toxicity. Identification of persistent disease or relapse is most often the trigger to intensify or re-initiate anti-neoplastic therapy, respectively. In the current era of NHL treatment, this determination is mostly based on imaging and clinical evaluations, tools with imperfect sensitivity and specificity. The availability of minimal residual disease (MRD) monitoring could transform treatment paradigms by allowing intensification of treatment in at-risk patients or early intervention for impending relapse. Novel methods based on polymerase chain reaction and next-generation sequencing are now being studied in NHL with promising results. This review outlines the current status of the field in the use of MRD techniques for diffuse large B-cell lymphoma, mantle cell lymphoma and follicular lymphoma. Specifically, we address their demonstrated and potential clinical utility in risk stratification, monitoring of remission status, and guiding interim and post-treatment escalation. Future applications of these techniques could identify novel markers of MRD, improve initial treatment selection, guide treatment escalation or de-escalation, and allow for real-time monitoring of patterns of clonal evolution, which together could redefine NHL treatment paradigms.

Detection of the circulating tumor DNAs in angioimmunoblastic T- cell lymphoma

Recent genetic studies identified that the disease-specific G17V RHOA mutation, together with mutations in TET2, DNMT3A, and IDH2, is a hallmark of angioimmunoblastic T cell lymphomas (AITL). The diagnostic value of these mutations is now being investigated. Circulating tumor DNAs (ctDNAs) may offer a non-invasive testing for diagnosis and disease monitoring of cancers. To investigate whether these mutations are useful markers for ctDNAs in AITL and its related lymphomas, we performed targeted sequencing for TET2, RHOA, DNMT3A, and IDH2 in paired tumors and cell-free DNAs from 14 patients at diagnosis. Eighty-three percent of mutations detected in tumors were also observed in cell-free DNAs. During the disease course, mutations were detectable in cell-free DNAs in a refractory case, while they disappeared in a chemosensitive case. These data suggest that the disease-specific gene mutations serve as sensitive indicators for ctDNAs and may also be applicable for non-invasive monitoring of minimal residual diseases in AITL.

High-throughput sequencing for noninvasive disease detection in hematologic malignancies

Noninvasive monitoring of minimal residual disease (MRD) has led to significant advances in personalized management of patients with hematologic malignancies. Improved therapeutic options and prolonged survival have further increased the need for sensitive tumor assessment that can inform treatment decisions and patient outcomes. At diagnosis or relapse of most hematologic neoplasms, malignant cells are often easily accessible in the blood as circulating tumor cells (CTCs), making them ideal targets to noninvasively profile the molecular features of each patient. In other cancer types, CTCs are generally rare and noninvasive molecular detection relies on circulating tumor DNA (ctDNA) shed from tumor deposits into circulation. The ability to precisely detect and quantify CTCs and ctDNA could minimize invasive procedures and improve prediction of clinical outcomes. Technical advances in MRD detection methods in recent years have led to reduced costs and increased sensitivity, specificity, and applicability. Among currently available tests, high-throughput sequencing (HTS)-based approaches are increasingly attractive for noninvasive molecular testing. HTS-based methods can simultaneously identify multiple genetic markers with high sensitivity and specificity without individual optimization. In this review, we present an overview of techniques used for noninvasive molecular disease detection in selected myeloid and lymphoid neoplasms, with a focus on the current and future role of HTS-based assays.