High rate of durable responses with undetectable minimal residual disease with front-line venetoclax and rituximab in young, fit patients with chronic lymphocytic leukemia and an adverse biological profile: results of the GIMEMA phase II LLC1518 - VERITAS study.

The GIMEMA phase II LLC1518 VERITAS trial investigated the efficacy and safety of front-line, fixed-duration venetoclax and rituximab (VenR) in combination in young (≤65 years), fit patients with chronic lymphocytic leukemia and unmutated IGHV and/or TP53 disruption. Treatment consisted of the venetoclax ramp-up, six monthly courses of the VenR combination, followed by six monthly courses of venetoclax as a single agent. A centralized assessment of minimal residual disease (MRD) was performed by allele-specific oligonucleotide polymerase chain reaction assay on the peripheral blood and bone marrow at the end of treatment (EOT) and during the follow-up. The primary endpoint was the complete remission rate at the EOT. Seventy-five patients were enrolled; the median age was 54 years (range, 38-65), 96% had unmutated IGHV, 12% had TP53 disruption, and 4% had mutated IGHV with TP53 disruption. The overall response rate at the EOT was 94.7%, with a complete remission rate of 76%. MRD was undetectable in the peripheral blood of 69.3% of patients and in the bone marrow of 58.7% of patients. The 12-month MRD-free survival in the 52 patients with undetectable MRD in the peripheral blood at the EOT was 73.1%. After a median follow-up of 20.8 months, no cases of disease progression were observed. Three patients had died, two due to COVID-19 and one due to tumor lysis syndrome. The first report of the VERITAS study shows that front-line VenR was associated with a high rate of complete remissions and durable response with undetectable MRD in young patients with chronic lymphocytic leukemia and unfavorable genetic characteristics. ClinicalTrials.gov identifier: NCT03455517.

Circulating cell-free DNA for target quantification in hematologic malignancies: Validation of a protocol to overcome pre-analytical biases.

Circulating tumor DNA (ctDNA) has become the most investigated analyte in blood. It is shed from the tumor into the circulation and represents a subset of the total cell-free DNA (cfDNA) pool released into the peripheral blood. In order to define if ctDNA could represent a useful tool to monitor hematologic malignancies, we analyzed 81 plasma samples from patients affected by different diseases. The results showed that: (i) the comparison between two different extraction methods Qiagen (Hilden, Germany) and Promega (Madison, WI) showed no significant differences in cfDNA yield, though the first recovered higher amounts of larger DNA fragments; (ii) cfDNA concentrations showed a notable inter-patient variability and differed among diseases: acute lymphoblastic leukemia and chronic myeloid leukemia released higher amounts of cfDNA than chronic lymphocytic leukemia, and diffuse large B-cell lymphoma released higher cfDNA quantities than localized and advanced follicular lymphoma; (iii) focusing on the tumor fraction of cfDNA, the quantity of ctDNA released was insufficient for an adequate target quantification for minimal residual disease monitoring; (iv) an amplification system proved to be free of analytical biases and efficient in increasing ctDNA amounts at diagnosis and in follow-up samples as shown by droplet digital PCR target quantification. The protocol has been validated by quality control rounds involving external laboratories. To conclusively document the feasibility of a ctDNA-based monitoring of patients with hematologic malignancies, more post-treatment samples need to be evaluated. This will open new possibilities for ctDNA use in the clinical practice.

Applicability of droplet digital polymerase chain reaction for minimal residual disease monitoring in Philadelphia-positive acute lymphoblastic leukaemia.

In Ph+ acute lymphoblastic leukaemia (Ph+ ALL), minimal residual disease (MRD) is the most relevant prognostic factor. Currently, its evaluation is based on quantitative real-time polymerase chain reaction (Q-RT-PCR). Digital droplet PCR (ddPCR) was successfully applied to several haematological malignancies. We analyzed 98 samples from 40 Ph+ ALL cases, the majority enrolled in the GIMEMA LAL2116 trial: 10 diagnostic samples and 88 follow-up samples, mostly focusing on positive non-quantifiable (PNQ) or negative samples by Q-RT-PCR to investigate the value of ddPCR for MRD monitoring. DdPCR BCR/ABL1 assay showed good sensitivity and accuracy to detect low levels of transcripts, with a high rate of reproducibility. The analysis of PNQ or negative cases by Q-RT-PCR revealed that ddPCR increased the proportion of quantifiable samples (p < 0.0001). Indeed, 29/54 PNQ samples (53.7%) proved positive and quantifiable by ddPCR, whereas 13 (24.1%) were confirmed as PNQ by ddPCR and 12 (22.2%) proved negative. Among 24 Q-RT-PCR-negative samples, 13 (54.1%) were confirmed negative, four (16.7%) resulted PNQ and seven (29.2%) proved positive and quantifiable by ddPCR. Four of 5 patients, evaluated at different time points, who were negative by Q-RT-PCR and positive by ddPCR experienced a relapse. DdPCR appears useful for MRD monitoring in adult Ph+ ALL.

Immunoglobulin kappa deleting element rearrangements are candidate targets for minimal residual disease evaluation in mantle cell lymphoma.

Minimal residual disease (MRD) assessment is of high clinical relevance in patients with mantle cell lymphoma (MCL). In mature B-cell malignancies, the presence of somatic hypermutations (SHM) in Variable-Diversity-Joining Heavy chain (VDJH) rearrangements leads to frequent mismatches between primers, probes, and the target, thus impairing tumor cells quantification. Alternative targets, such as immunoglobulin kappa-deleting-element (IGK-Kde) rearrangements, might be suitable for MRD detection. We aimed at evaluating the applicability of IGK-Kde rearrangements for MRD quantification in MCL patients by real-time quantitative polymerase chain reaction (RQ-PCR)/digital-droplet-PCR (ddPCR). IGK screening was performed on bone marrow samples from two cohorts: the first from Turin (22 patients enrolled in the FIL-MCL0208 trial, NCT02354313) and the second from Rome (15 patients). IGK-Kde rearrangements were found in 76% (28/37) of cases, representing the sole molecular marker in 73% (8/11) of IGH-BCL1/IGH negative cases. MRD RQ-PCR monitoring was possible in 57% (16/28) of cases, showing a 100% concordance with the conventional targets. However, the frequent background amplification affected the sensitivity of the assay, that was lower in MCL compared to acute lymphoblastic leukemia and in line with multiple myeloma published results. ddPCR had a good concordance with RQ-PCR and it might help to identify false positive/negative results. From a clinical perspective, we suggest that IGK-Kde can be a candidate target for MRD monitoring and deserves a validation of its predictive value in prospective MCL series.

Minimal residual disease (MRD) in non-Hodgkin lymphomas: Interlaboratory reproducibility on marrow samples with very low levels of disease within the FIL (Fondazione Italiana Linfomi) MRD Network.

In 2009, the four laboratories of the Fondazione Italiana Linfomi (FIL) minimal residual disease (MRD) Network started a collaborative effort to harmonize and standardize their methodologies at the national level, performing quality control (QC) rounds for follicular lymphoma (FL) and mantle cell lymphoma (MCL) MRD assessment. In 16 QC rounds between 2010 and 2017, the four laboratories received 208 bone marrow (BM) samples (126 FL; 82 MCL); 187 were analyzed, according to the EuroMRD Consortium guidelines, by both nested (NEST) polymerase chain reaction (PCR) and real-time quantitative (RQ) PCR for BCL2/IGH MBR or IGHV rearrangements. Here, we aimed at analyzing the samples that challenged the interlaboratory reproducibility and data interpretation. Overall, 156/187 BM samples (83%) were concordantly classified as NEST+/RQ+ or NEST-/RQ- by all the four laboratories. The remaining 31 samples (17%) resulted alternatively positive and negative in the interlaboratory evaluations, independently of the method and the type of rearrangement, and were defined "borderline" (brd) samples: 12 proved NEST brd/RQ brd, 7 NEST-/RQ brd, 10 NEST brd/RQ positive not quantifiable (PNQ), and 2 NEST brd/RQ-. Results did not change even increasing the number of replicates/sample. In 6/31 brd samples, droplet digital PCR (ddPCR) was tested and showed no interlaboratory discordance. Despite the high interlaboratory reproducibility in the MRD analysis obtained and maintained by the QC round strategy, samples with the lowest MRD levels can still represent a challenge: 17% (31/187) of our samples showed discordant results in interlaboratory assessments, with 6.4% (12/187) remained brd even applying the two methods. Thus, although representing a minority, brd samples are still problematic, especially when a clinically oriented interpretation of MRD results is required. Alternative, novel methods such as ddPCR and next-generation sequencing have the potential to overcome the current limitations.

Comparative analysis between RQ-PCR and digital droplet PCR of BCL2/IGH gene rearrangement in the peripheral blood and bone marrow of early stage follicular lymphoma.

BCL2/IGH rearrangements were analysed by polymerase chain reaction (PCR) at diagnosis in paired peripheral blood (PB) and bone marrow (BM) samples from 67 patients with stage I/II follicular lymphoma (FL). Real time quantitative PCR (RQ-PCR) and digital droplet PCR (ddPCR) were performed in cases with a major breakpoint region (MBR+) at diagnosis and after localized radiotherapy and rituximab administration in order to investigate the applicability of ddPCR. The overall ddPCR/RQ-PCR concordance was 81·9% (113/138 samples) and 97·5% in the 40/138 with quantifiable disease (RQ-PCR≥10-5 ). At baseline, ddPCR allowed the recovery of a MBR+ marker in 8/18 (44·4%) samples that resulted MBR-negative/minor cluster region-negative/minor BCL2-negative by qualitative PCR. Moreover, the tumour burden at diagnosis significantly predicted progression-free survival (PSF) only when quantified by ddPCR. Paired PB and BM samples analysis demonstrated a high concordance in the detection of BCL2/IGH+ cells by qualitative and quantitative methods; in particular, 40/62 samples were positive by ddPCR (25 PB+/BM+; 9 PB+/BM-; 6 PB-/BM+), with 34/40 (85%) identified by the study of PB only. In conclusion, in localized FL, ddPCR is a promising tool for monitoring minimal residual disease (MRD) that is at least comparable to RQ-PCR and potentially more accurate. PB is a suitable source for serial BCL2/IGH MRD assessments, regardless of the methodology utilized.

Comparative analysis between RQ-PCR and digital-droplet-PCR of immunoglobulin/T-cell receptor gene rearrangements to monitor minimal residual disease in acute lymphoblastic leukaemia.

Real-time quantitative polymerase chain reaction (RQ-PCR) is a standardized tool for minimal residual disease (MRD) monitoring in acute lymphoblastic leukaemia (ALL). The applicability of this technology is limited by the need of a standard curve based on diagnostic DNA. The digital droplet PCR (ddPCR) technology has been recently applied to various medical fields, but its use in MRD monitoring is under investigation. In this study, we analysed 50 ALL cases by both methods in two phases: in the first, we established analytical parameters to investigate the applicability of this new technique; in the second, we analysed MRD levels in 141 follow-up (FU) samples to investigate the possible use of ddPCR for MRD monitoring in ALL patients. We documented that ddPCR has sensitivity and accuracy at least comparable to those of RQ-PCR. Overall, the two methods gave concordant results in 124 of the 141 analysed MRD samples (88%, P = 0·94). Discordant results were found in 12% borderline cases. The results obtained prove that ddPCR is a reliable method for MRD monitoring in ALL, with the advantage of quantifying without the need of the calibration curves. Its application in a cohort of patients with a longer FU will conclusively define its clinical predictive value.

Whole-genome amplification for the detection of molecular targets and minimal residual disease monitoring in acute lymphoblastic leukaemia.

Accurate genomic characterization requires sufficient amounts of optimal quality DNA. An approach for increasing the DNA amount is the whole-genome amplification (WGA) method. We applied WGA to the molecular quantification and minimal residual disease (MRD) evaluation of acute lymphoblastic leukaemia (ALL), aiming to compare the results obtained from genomic DNA and amplified DNA with WGA, and to evaluate the applicability and the reliability of WGA-DNA. Twenty paired samples from adult ALL patients were sequenced to identify the functional germline V-D-J segment at diagnosis; real-time quantitative polymerase chain reaction (RQ-PCR) quantitative analysis was performed both at diagnosis and follow-up. Genomic DNA and WGA-DNA screening identified equivalent 87 rearrangements. At diagnosis, the quantitative evaluation of genomic DNA samples showed 1 logarithm difference to WGA-DNA samples; these levels are comparable, being within the degree of acceptability and confidence. In the follow-up samples, RQ-PCR analysis on genomic DNA and WGA showed concordant MRD results in 16/18 samples, while 2/18 were MRD-positive outside the quantitative range by RQ-PCR (i.e. <5 × 10(-5)) on genomic DNA and MRD-negative on WGA-DNA. WGA-DNA enables: (i) the design of accurate targets for MRD evaluation in ALL patients, (ii) accurate disease quantification at diagnosis, (iii) MRD quantification comparable to genomic DNA.

Local radiotherapy and measurable residual disease-driven immunotherapy in patients with early-stage follicular lymphoma (FIL MIRO): final results of a prospective, multicentre, phase 2 trial.

BACKGROUND: The mainstay of treatment for early-stage follicular lymphoma is local radiotherapy, with a possible role for anti-CD20 monoclonal antibody (mAb). We aimed to evaluate the effect of these treatments using a measurable residual disease (MRD)-driven approach. METHODS: This prospective, multicentre, phase 2 trial was conducted at 27 centres of the Fondazione Italiana Linfomi (FIL) in Italy. Eligible participants were adults (≥18 years) with newly diagnosed, histologically confirmed follicular lymphoma (stage I or II; grade I-IIIa). Patients were initially treated with 24 Gy involved-field radiotherapy over 12 days; those who were MRD-positive after radiotherapy or during follow-up received eight intravenous doses (1000 mg per dose; one dose per week) of the anti-CD20 mAb ofatumumab. The primary endpoint was the proportion of patients who were MRD-positive after involved-field radiotherapy and became MRD-negative after ofatumumab treatment. Patients were included in the primary endpoint analysis population if they were positive for BCL2::IGH rearrangement at enrolment in peripheral blood or bone marrow samples. MRD positivity was defined as the persistence of BCL2::IGH rearrangement in peripheral blood or bone marrow, assessed centrally by laboratories of the FIL MRD Network. The trial was registered with EudraCT, 2012-001676-11. FINDINGS: Between May 2, 2015, and June 1, 2018, we enrolled 110 participants, of whom 106 (96%) were eligible and received involved-field radiotherapy. Of these, 105 (99%) were White, one (1%) was Black, 50 (47%) were male, and 56 (53%) were female. Of 105 participants in whom BCL2::IGH status was evaluable, 32 (30%) had a detectable BCL2::IGH rearrangement at baseline. After radiotherapy, 12 (40%) of 30 patients reached MRD-negative status, which was long-lasting (at least 36 or 42 months) in three (25%). In those who were MRD-positive after radiotherapy, ofatumumab induced MRD-negativity in 23 (92%; 95% CI 74-99) of 25 evaluable patients. After a median follow-up of 46·1 months (IQR 42·8-50·8), 14 (61%) of these 23 patients remain in complete response and are MRD-negative. The most common grade 3-4 adverse events were infusion-related reactions, observed in four patients. INTERPRETATION: Local radiotherapy is frequently not associated with the eradication of follicular lymphoma. An MRD-driven, anti-CD20 monoclonal antibody consolidation enables molecular remission to be reached in almost all patients and is associated with a reduced incidence of relapse over time. A clinical advantage of an MRD-driven consolidation is therefore suggested. FUNDING: AIRC Foundation for Cancer Research in Italy, Novartis International, and GlaxoSmithKline.

Optimizing Molecular Minimal Residual Disease Analysis in Adult Acute Lymphoblastic Leukemia.

Minimal/measurable residual disease (MRD) evaluation has resulted in a fundamental instrument to guide patient management in acute lymphoblastic leukemia (ALL). From a methodological standpoint, MRD is defined as any approach aimed at detecting and possibly quantifying residual neoplastic cells beyond the sensitivity level of cytomorphology. The molecular methods to study MRD in ALL are polymerase chain reaction (PCR) amplification-based approaches and are the most standardized techniques. However, there are some limitations, and emerging technologies, such as digital droplet PCR (ddPCR) and next-generation sequencing (NGS), seem to have advantages that could improve MRD analysis in ALL patients. Furthermore, other blood components, namely cell-free DNA (cfDNA), appear promising and are also being investigated for their potential role in monitoring tumor burden and response to treatment in hematologic malignancies. Based on the review of the literature and on our own data, we hereby discuss how emerging molecular technologies are helping to refine the molecular monitoring of MRD in ALL and may help to overcome some of the limitations of standard approaches, providing a benefit for the care of patients.

Human herpesvirus-8-positive primary effusion lymphoma in HIV-negative patients: Single institution case series with a multidisciplinary characterization.

BACKGROUND: Primary effusion lymphoma (PEL) is a very rare non-Hodgkin lymphoma caused by human herpesvirus-8 (HHV8) that grows in liquid phase within body cavities. The diagnosis of PEL is based on cytology but requires confirmatory ancillary tests. PEL occurs mainly in association with HIV infection. This study describes 9 cases of PEL in HIV-negative patients and compares their characteristics with 10 HIV-associated cases of PEL diagnosed at a single institution in Italy between 1995 and 2019. METHODS: Clinical records were reviewed for demographic data, comorbidities, laboratory abnormalities, and outcome. PEL samples were evaluated for cytomorphology, immunophenotype, immunoglobulin (IG)/T cell receptor (TR) rearrangements, and HHV8 and Epstein-Barr virus (EBV) viral loads in effusion supernatants. RESULTS: HIV-unrelated PEL occurred in 8 elderly patients (7 men, 1 woman) and 1 young adult with primary antibody deficiency. Cytology revealed HHV8-positive lymphoma cells lacking B/T cell antigens and exhibiting 2 cell patterns (polymorphous or monotonous). IG was clonally rearranged in all cases; aberrant TRG occurred in 2 cases. Effusion supernatants had more than 106 HHV8 DNA copies per mL and variable loads of EBV DNA. Compared with HIV-associated PEL, the HIV-negative cohort was characterized by older age, less frequent association with Kaposi sarcoma and/or multicentric Castleman disease, comparable but less abnormal laboratory parameters, and a nonsignificant survival benefit. PEL cases with low apoptosis were associated with better prognosis. CONCLUSION: To the best of our knowledge, our case series of HIV-unrelated PEL is the largest thus far, expands the spectrum of cytological findings, and supports the need for a multidisciplinary approach in the diagnostic workup.

Droplet Digital PCR Improves IG-/TR-based MRD Risk Definition in Childhood B-cell Precursor Acute Lymphoblastic Leukemia.

Minimal residual disease (MRD) is the most powerful prognostic factor in pediatric acute lymphoblastic leukemia (ALL). Real-time quantitative polymerase chain reaction (RQ-PCR) represents the gold standard for molecular MRD assessment and risk-based stratification of front-line treatment. In the protocols of the Italian Association of Pediatric Hematology and Oncology (AIEOP) and the Berlin-Frankfurth-Munschen (BFM) group AIEOP-BFM ALL2009 and ALL2017, B-lineage ALL patients with high RQ-PCR-MRD at day+33 and positive at day+78 are defined slow early responders (SERs). Based on results of the AIEOP-BFM ALL2000 study, these patients are treated as high-risk also when positive MRD signal at day +78 is below the lower limit of quantification of RQ-PCR ("positive not-quantifiable," POS-NQ). To assess whether droplet digital polymerase chain reaction (ddPCR) could improve patients' risk definition, we analyzed MRD in 209 pediatric B-lineage ALL cases classified by RQ-PCR as POS-NQ and/or negative (NEG) at days +33 and/or +78 in the AIEOP-BFM ALL2000 trial. ddPCR MRD analysis was performed on 45 samples collected at day +78 from SER patients, who had RQ-PCR MRD ≥ 5.0 × 10-4 at day+33 and POS-NQ at day+78 and were treated as medium risk (MR). The analysis identified 13 of 45 positive quantifiable cases. Most relapses occurred in this patients' subgroup, while ddPCR NEG or ddPCR-POS-NQ patients had a significantly better outcome (P < 0.001). Overall, in 112 MR cases and 52 standard-risk patients, MRD negativity and POS-NQ were confirmed by the ddPCR analysis except for a minority of cases, for whom no differences in outcome were registered. These data indicate that ddPCR is more accurate than RQ-PCR in the measurement of MRD, particularly in late follow-up time points, and may thus allow improving patients' stratification in ALL protocols.

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.