Circulating Tumor DNA in Diffuse Large B-Cell Lymphoma: from Bench to Bedside?

OPINION STATEMENT: Diffuse large B-cell lymphoma (DLBCL) is a curable disease with variable outcomes due to underlying heterogeneous clinical and molecular features-features that are insufficiently characterized with our current tools. Due to these limitations, treatment largely remains a "one-size-fits-all" approach. Circulating tumor DNA (ctDNA) is a novel biomarker in cancers that is increasingly utilized for risk stratification and response assessment. ctDNA is readily detectable from the plasma of patients with DLBCL but has not yet been incorporated into clinical care to guide treatment. Here, we describe how ctDNA sequencing represents a promising technology in development to personalize the care of patients with DLBCL. We will review the different types of ctDNA assays being studied and the rapidly growing body of evidence supporting the utility of ctDNA in different treatment settings in DLBCL. Risk stratification by estimation of tumor burden and liquid genotyping, molecular response assessment during treatment, and monitoring for measurable residual disease (MRD) to identify therapy resistance and predict clinical relapse are all potential applications of ctDNA. It is time for clinical trials in DLBCL to utilize ctDNA as an integral biomarker for patient selection, response-adapted designs, and surrogate endpoints. As more ctDNA assays become commercially available for routine use, clinicians should consider liquid biopsy when treatment response is equivocal on imaging. Incorporating MRD may also guide decision-making if patients experience severe treatment toxicities. Though important barriers remain, we believe that ctDNA will soon be ready to transition from bench to bedside to individualize treatment for our patients with DLBCL.

Measurable Residual Disease Monitoring in Lymphoma.

PURPOSE OF REVIEW: The utility of analyzing circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and disease in the bone marrow as an adjunctive tool in caring for hematologic cancer patients is expanding. This holds true for lymphoma where these biomarkers are being explored as a means of genotyping and quantifying disease. Regarding the latter, they can be used to monitor measurable residual disease (MRD) during and after treatment. This holds potential for aiding clinical decisions amidst treatment, detecting earlier relapse, and improving prognostication. Here, we review the evidence to support these applications in a variety of lymphoma subtypes. RECENT FINDINGS: Numerous clinical trials across a variety of lymphomas have demonstrated value in MRD monitoring. MRD monitoring is often prognostic for progression free survival (PFS) and even overall survival (OS) at several time points in a disease course, particularly when utilizing serial measurements. With regards to tailoring treatment, there are a growing number of trials examining MRD-adaptive treatment strategies to intensify or de-escalate treatment to individualize care. Lastly, MRD monitoring has been utilized successfully in detecting earlier relapse when compared to more standard methods of clinical surveillance such as radiographic assessment. Although not routinely implemented into clinical practice, MRD monitoring in lymphoma is helping shape the future landscape of this disease by aiding in prognostication, guiding therapy, and detecting earlier relapse. Steps to standardize and further examine this technology prospectively are being taken to bring MRD monitoring to the forefront of the field.

A phase 1/2 study of lenalidomide and obinutuzumab with CHOP for newly diagnosed DLBCL.

Diffuse large B-cell lymphoma (DLBCL) can be cured with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP); however, one-third of patients experience refractory or relapsed disease. Studies comparing R-CHOP with modified regimens replacing R with obinutuzumab (O) or adding lenalidomide (L) did not result in improved outcomes; however, L and O together may enhance natural killer-cell mediated antibody-dependent cellular toxicity when paired with CHOP. Here, we report on a phase 1b/2 study of 53 patients with newly diagnosed DLBCL who received 6 cycles of LO-CHOP. The end of treatment overall and complete response rates of the 50 evaluable patients were 98% and 90%, respectively. After a median follow-up of 4.5 years, the 4-year progression free and overall survival rates were 87.4% and 91.3%, respectively. Grade 3 to 4 adverse events were experienced by 70% of patients, including neutropenia (38%), thrombocytopenia (17%), fatigue (13%), and neutropenic fever (13%). Of the 33 patients profiled with circulating tumor DNA (ctDNA) sequencing, 31 (94%) had detectable pretreatment ctDNA with cancer personalized profiling by deep sequencing, 24 (73%) were classifiable by the LymphGen classifier, and 15/20 (75%) and 12/17 (71%) patients achieved early and major molecular responses after 1 and 2 cycles, respectively. Using phased variant enrichment and detection sequencing, 16/18 evaluable patients (89%) showed no detectable ctDNA after at least 5 cycles of LO-CHOP. LO-CHOP demonstrates high efficacy and tolerability in newly diagnosed DLBCL, leading to a high rate of undetectable minimal residual disease by ctDNA. This trial has been registered at www.clinicaltrials.gov as NCT02529852.

Positron emission tomography derived metrics in relapsed or refractory large B-cell lymphoma with residual disease before autologous stem cell transplant.

Salvage chemotherapy followed by high-dose chemotherapy and autologous stem cell transplantation (ASCT) is a potentially curative treatment for patients with relapsed or refractory large B-cell lymphoma (rrLBCL) with chemosensitive disease. A18 F-fluorodeoxyglucose positron emission tomography (PET) scan after salvage chemotherapy is used to assess response and eligibility for ASCT, but metrics for chemosensitivity in patients with residual disease are not well defined. We performed a single-centre retrospective analysis of 92 patients with a partial response or stable disease after salvage chemotherapy for rrLBCL who received ASCT to investigate PET-derived parameters and their prognostic utility. The Deauville 5-point Scale (D-5PS) score, maximum standardised uptake value (SUVmax ), total metabolic tumour volume (TMTV), and total lesion glycolysis (TLG) were calculated from the post-salvage/pre-ASCT PET scan. The 5-year progression-free survival (PFS) and overall survival (OS) rates were 40% and 54% respectively. A D-5PS score of 5 (p = 0.0082, hazard ratio [HR] 2.09), high SUVmax (p = 0.0015, HR 2.48), TMTV (p = 0.035, HR 1.83) and TLG (p = 0.0036, HR 2.27) were associated with inferior PFS. A D-5PS score of 5 (p = 0.030, HR 1.98) and high SUVmax (p = 0.0025, HR 2.55) were associated with inferior OS. PET-derived parameters may help prognosticate outcomes after ASCT in patients with rrLBCL with residual disease after salvage chemotherapy.

Impact of conditioning chemotherapy on lymphocyte kinetics and outcomes in LBCL patients treated with CAR T-cell therapy.

Conditioning chemotherapy (CCT) has been shown to be essential for optimal efficacy of chimeric antigen receptor (CAR) T-cell therapy. Here, we determined whether the change in absolute lymphocyte count, referred to as delta lymphocyte index (DLIx), may serve as a surrogate marker for pharmacodynamic effects of CCT and whether it associated with germline genetic variants in patients with large B-cell lymphoma (LBCL). One-hundred and seventy-one patients were included, of which 86 (50%) received bridging therapy post-leukapheresis. Median DLIx was 0.5 × 109/L (range, 0.01-2.75 × 109/L) and was significantly higher in patients who achieved complete response (p = 0.04). On multivariate analysis, low DLIx was associated only with use of bridging therapy (odds ratio 0.4, 95% CI 0.2-0.8, p = 0.007). Low DLIx was independently associated with shorter progression-free (p = 0.02) and overall survival (p = 0.02). DLIx was associated with genetic variations related to drug metabolism and macrophage biology such as ABCB1, MISP and CPVL. The impact of CCT on lymphocyte count is affected by use of bridging therapy but change in lymphocyte count is independently associated with efficacy. Studies aimed at investigating macrophage biology in this setting may suggest strategies to increase the efficacy of CCT and improve outcomes.

Broadening the MIND: Tafasitamab and Lenalidomide versus Synthetic Controls.

Tafasitamab and lenalidomide were approved for second-line treatment of diffuse large B-cell lymphoma (DLBCL) based on a single-arm phase II study. This combination was superior to routine immunochemotherapy regimens when comparing matched observational cohorts. "Synthetic" control groups may support use of novel DLBCL therapies in the absence of randomized studies. See related article by Nowakowski et al., p. 4003.

Risk assessment with low-pass whole-genome sequencing of cell-free DNA before CD19 CAR T-cell therapy for large B-cell lymphoma.

Patients with relapsed or refractory large B-cell lymphomas (rrLBCL) can achieve long-term remission after CD19 chimeric antigen receptor T-cell therapy (CART19). However, more than half of recipients will experience treatment failure. Thus, approaches are needed to identify high-risk patients who may benefit from alternative or consolidative therapy. We evaluated low-pass whole-genome sequencing (lpWGS) of cell-free DNA (cfDNA) before CART19 as a new approach for risk stratification. We performed lpWGS on pretreatment plasma samples from 122 patients at time of leukapheresis who received standard-of-care CART19 for rrLBCL to define DNA copy number alterations (CNAs). In multivariable selection, high focal CNA score (FCS) denoting genomic instability was the most significant pretreatment variable associated with inferior 3-month complete response rates (28% vs 56%, P = .0029), progression-free survival (PFS; P = .0007; hazard ratio, 2.11), and overall survival (OS; P = .0026; hazard ratio, 2.10). We identified 34 unique focal CNAs in 108 (89%) patients; of these, deletion 10q23.3 leading to loss of FAS death receptor was the most highly associated with poor outcomes, leading to inferior PFS (P < .0001; hazard ratio, 3.49) and OS (P = .0027; hazard ratio, 2.68). By combining FCS with traditional markers of increased tumor bulk (elevated lactate dehydrogenase and >1 extranodal site), we built a simple risk model that could reliably risk stratify patients. Thus, lpWGS of cfDNA is a minimally invasive assay that could rapidly identify high-risk patients and may guide patient selection for and targeted therapies to evaluate in future clinical trials.

TP53-altered chronic lymphocytic leukemia treated with firstline Bruton's tyrosine kinase inhibitor-based therapy: A retrospective analysis.

Long-term follow up of prospective studies has shown that continuous Bruton's tyrosine kinase inhibitor (BTKi) therapy leads to durable remissions in previously untreated patients with TP53-altered chronic lymphocytic leukemia (CLL); however, it is unknown how variant allele frequency (VAF) of TP53 mutation (TP53-m) or percentage of cells with deletion of chromosome 17p [del(17p)] influences efficacy of firstline BTKi. We performed a retrospective analysis of 130 patients with CLL with baseline del(17p) and/or TP53-m treated with BTKi with or without the BCL2 inhibitor venetoclax (VEN) and with or without CD20 antibody in the firstline setting. A total of 104/130 (80%) patients had del(17p). TP53-m was noted in 89/110 (81%) patients tested; there were 101 unique TP53-m with an available VAF. The 4-year progression-free survival (PFS) and overall survival (OS) rates were 72.9% and 83.6%. No baseline characteristics including IGHV mutation status and number of TP53 alterations were associated with significant differences in PFS or OS, though a trend toward shorter PFS with increasing karyotypic complexity (hazard ratio 1.08, p = .066) was observed. Del(17p) was identified in <25% of cells in 26/104 (25%) of patients, and 28/101 (28%) of TP53-m were low-burden with a VAF of <10%; outcomes of these patients were similar to those with high-burden lesions. This study suggests that low-burden TP53 alterations should not be ignored when assessing genomic risk in CLL in the era of targeted therapy.

A prospective study on early PET/CT scans during the first cycle of salvage chemotherapy for relapsed or refractory diffuse large B-cell lymphoma.

Many patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) will not respond to platinum-containing salvage chemotherapy. Predicting treatment failure earlier could help clinicians minimize chemotherapy toxicities for non-responders in favor of other treatments. We conducted a pilot study where 2 early PET/CTs were obtained on days 4 (D4) and 21 (D21) of cycle 1 (C1) of salvage therapy for DLBCL. Twenty-five patients were enrolled and have evaluable data. Ten (40%) had an unplanned therapy change after C1 and before end-of-treatment (EOT) evaluation due to treatment failure on early PET/CT as interpreted by the treating physician. Early PET/CT response at D4 or D21 was not associated with EOT response in evaluable patients. Disease specific survival was longer for patients with a persistent response on both D4 and D21 (p = 0.042). Early PET/CT may predict salvage chemotherapy failure and could inform future clinical trials investigating early therapy change to non-chemotherapy treatments.

First-Line Therapy for Chronic Lymphocytic Leukemia: Bruton Tyrosine Kinase or BCL2 or Both?

Novel therapies largely have replaced chemoimmunotherapy as optimal first-line treatment of chronic lymphocytic leukemia (CLL). Approved novel therapies for CLL in the first-line setting include Bruton tyrosine kinase inhibitors, ibrutinib and acalabrutinib, and the BCL2 inhibitor venetoclax. Each of these novel agents has its own unique attributes and they have not been compared head to head in randomized trials. This review summarizes the pivotal trials that led to the approval of novel agents and compares the features of each agent to guide treatment decisions in treatment-naïve CLL. Ongoing studies investigating combinations of novel agents in the first-line setting also are discussed.

Clinical and molecular characteristics and treatment patterns of adolescent and young adult patients with chronic lymphocytic leukaemia.

Chronic lymphocytic leukaemia (CLL) rarely presents in adolescent and young adult (AYA) patients (patients aged 15-39 years). Disease characteristics and outcomes of AYA patients with CLL are not well understood, particularly in the era of novel oral targeted therapies. We analysed outcomes of 227 AYA patients with CLL diagnosed in the last two decades and evaluated at our institution. Median time to first treatment (TTFT) was 2·2 years, and five- and 10-year overall survival (OS) were 90% and 78%, respectively. Pre-treatment elevated beta 2-microglobulin, advanced Rai stage, del(11q) or del(17p) by FISH, unmutated IGHV and CD38 positivity were associated with both shorter TTFT and OS. Within the subgroup of patients who received oral targeted therapy at any time, del(11q) or del(17p) and complex karyotype were associated with shorter OS. First-line treatment choice was significantly associated with time to second treatment (P < 0·001). Patients harbouring del(11q) or del(17p) experienced shorter time to Richter transformation and were more likely to undergo an allogeneic stem cell transplant. There was a significant association between age and both OS and time to Richter transformation. Our study is the first analysis of AYA patients with CLL with a large number of patients treated with oral targeted therapies.

Why R-CHOP + X is not enough: lessons learned and next steps in the mission to improve frontline therapy for diffuse large B-cell lymphoma.

Two-thirds of newly diagnosed cases of diffuse large B-cell lymphoma (DLBCL) are cured with R-CHOP, an immunochemotherapy regimen that has been the standard of care for almost two decades. Ongoing molecular characterization of DLBCL has revealed a heterogeneous disease comprised of multiple subtypes based on putative cell of origin or somatic mutations with unique oncogenic signaling pathways. The door has been opened to the use of novel agents that target the specific molecular vulnerabilities of DLBCL, but despite this, multiple randomized studies have not identified a suitable drug 'X' to combine with R-CHOP. This report will review recent attempts to add individual novel agents to R-CHOP in the mission to improve frontline treatment for DLBCL and discuss promising ongoing studies. It will offer potential strategies to explore when designing future clinical trials, including exploiting synergy between multiple novel agents.

Interim PET/CT Result Is Not Predictive of Survival in Patients With MYC-rearranged Non-Burkitt Aggressive B-cell Lymphoma.

BACKGROUND: Patients with a diagnosis of MYC-rearranged non-Burkitt aggressive B-cell lymphoma (MYC-R), including those with double hit lymphoma, are at high risk of developing relapsed/refractory disease, even if treated with intensive front-line immunochemotherapy. It is common in clinical practice and clinical trials to perform an interim positron emission tomography (PET)/computed tomography (CT) scan (iPET) during front-line therapy for diffuse large B-cell lymphoma. However, the utility of the iPET result for MYC-R patients for predicting outcomes is unclear. PATIENTS AND METHODS: We performed a single-center retrospective study with centralized pathologic review and PET/CT image acquisition and interpretation for 28 MYC-R patients. The patients received front-line therapy with R-CHOP (rituximab, cyclophosphamide, hydroxydaunorubicin [doxorubicin], Oncovin [vincristine], prednisone) or intensive immunochemotherapy. RESULTS: Eight patients had iPET-positive (iPET+) and 20 patients had iPET-negative (iPET-) results using the Deauville visual assessment criteria. At a median follow-up length of 30.4 months, progression-free survival was 65% and overall survival was 76%, neither of which differed significantly between the iPET- and iPET+ patients. The positive predictive value of iPET for progression at 30 months was 25%, and the negative predictive value was 65%. CONCLUSION: Although patients with MYC-R lymphoma have been reported to be at high risk of primary treatment failure, this was not predicted by iPET+ results. Thus, the iPET result should not be used to guide changes in front-line or consolidative therapy for these patients.