Detectable Measurable Residual Disease Research Articles

Comparison of immunoglobulin high-throughput sequencing MRD in bone marrow and peripheral blood in pediatric B-ALL: A report from the Children's Oncology Group AALL1731.

10014 Background: Minimal (measurable) residual disease (MRD) at end of induction (EOI) therapy is a strong predictor of outcome in pediatric B-ALL. Currently, EOI MRD is assessed in bone marrow (BM). We hypothesized that the highly sensitive assay, high-throughput sequencing (HTS) of immunoglobulin loci, can effectively monitor MRD in peripheral blood (PB) and may provide a less invasive way to track therapy response. Methods: We conducted HTS MRD on paired EOI BM and PB samples from 808 NCI standard risk (SR) pediatric B-ALL patients enrolled on Children’s Oncology Group study AALL1731 (NCT03914625). We determined the correlation between BM and PB HTS MRD via Spearman’s rank correlations. We calculated the BM/PB MRD ratio and compared these by subgroup using Kruskal-Wallis tests. We defined subgroups by cytogenetics (cyto) ( ETV6::RUNX1, double trisomies of chromosome 4 and 10 (DT), Unfavorable (hypodiploidy, iAMP21, or KMT2A-rearranged), or Neutral (lacking ETV6::RUNX1, DT, or unfavorable)), and risk group (SR-average (AVG) and SR-High). Flow cytometry-defined EOI BM MRD was < 0.01% for all SR-AVG patients (N = 623) and ≥0.01% for selected SR-High patients (N = 185). Results: There was strong correlation between PB and BM HTS MRD with an overall correlation coefficient of 0.75 (P < 0.001). Correlation was similar by cytogenetics: ETV6::RUNX1, 0.69 (N = 63; P < 0.001), DT, 0.75 (N = 147; P < 0.001), Neutral, 0.74 (N = 580; P < 0.001), and Unfavorable, 0.66(N = 18; P = 0.003). For risk groups, correlation for SR-AVG was 0.67 (p < 0.001) and SR-High, 0.64 (p < 0.001). Of the 591 SR-AVG patients with detectable BM HTS MRD, PB HTS MRD was detectable in 474 (80.2%), undetectable in 94 (15.9%) and indeterminate (no leukemic cell detected and < 500,000 total cells in sample) in 23 (3.9%). Among 182 SR-High patients with detectable BM HTS MRD, 175 (96.2%) had detectable PB HTS MRD. Disease burden was higher in the BM than PB with a significantly higher BM/PB ratio in SR-High compared to SR-AVG patients (median 16.5 vs 2.6, P < 0.001). The median BM/PB ratio also varied by cytogenetics with those with Unfavorable cyto having the highest ratio (15.3 vs 6.3 in DT, 3.8 in ETV6::RUNX1, 3.1 in Neutral; P = 0.013). Conclusions: This is the largest analysis of paired B-ALL BM/PB HTS MRD to date. We show strong correlation between PB and BM across risk and cytogenetic groups. The ratio of BM/PB MRD varied and was highest among patients with Unfavorable cyto suggesting BM tropism. Importantly, PB MRD was detectable in nearly all patients with flow EOI BM MRD ≥0.01%, a threshold warranting therapy intensification. However, most patients with EOI BM flow MRD < 0.01% also had detectable PB HTS MRD. Thus, PB HTS MRD may provide a useful adjunct for screening and clinical management of B-ALL patients. Defining a PB HTS MRD threshold useful for risk stratification will require correlation with outcome.

How I treat newly diagnosed acute lymphoblastic leukemia.

Treatment algorithms differ for adult patients with Philadelphia-negative (Ph-) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). For Ph- ALL intensive induction-consolidation chemotherapy using "pediatric-inspired" protocols is a standard of care. Allogeneic hematopoietic cell transplantation (allo-HCT) from either an HLA-matched sibling, unrelated or haploidentical donor should be considered for patients with high estimated risk of relapse. Inadequate response at the level of measurable residual disease (MRD) is the strongest adverse prognostic factor. Patients with B-ALL and detectable MRD should be treated with blinatumomab. In the future, the use of blinatumomab and/or inotuzumab ozogamycin in addition to first-line chemotherapy may become a new standard of care reducing the role of allo-HCT. For patients with Ph+ ALL, tyrosine kinase inhibitors (TKI) are the most important components of treatment protocols, while the intensity of chemotherapy may be reduced. Allo-HCT is recommended for all patients treated with imatinib along with low-intensity chemotherapy. Results of phase-II studies using front-line dasatinib or ponatinib in sequence or in combination with blinatumomab are very promising. Such a strategy may allow the avoidance of systemic chemotherapy. The future role of allo-HCT in this context appears uncertain.

Acalabrutinib, venetoclax, and obinutuzumab in relapsed/refractory CLL: final efficacy and ctDNA analysis of the CLL2-BAAG trial

AbstractThe phase 2 CLL2-BAAG trial tested the measurable residual disease (MRD)–guided triple combination of acalabrutinib, venetoclax, and obinutuzumab after optional bendamustine debulking in 45 patients with relapsed/refractory chronic lymphocytic leukemia (CLL). MRD was measured by flow cytometry (FCM; undetectable MRD <10–4) in peripheral blood (PB) and circulating tumor DNA (ctDNA) using digital droplet polymerase chain reaction of variable-diversity-joining (VDJ) rearrangements and CLL-related mutations in plasma. The median number of previous treatments was 1 (range, 1-4); 18 patients (40%) had received a Bruton tyrosine kinase inhibitor (BTKi) and/or venetoclax before inclusion, 14 of 44 (31.8%) had TP53 aberrations, and 34 (75.6%) had unmutated immunoglobulin heavy-chain variable region genes. With a median observation time of 36.3 months and all patients off-treatment for a median of 21.9 months, uMRD <10–4 in PB was achieved in 42 of the 45 patients (93.3%) at any time point, including 17 of 18 (94.4%) previously exposed to venetoclax/BTKi and 13 of 14 (92.9%) with TP53 aberrations. The estimated 3-year progression-free and overall survival rates were 85.0% and 93.8%, respectively. Overall, 585 paired FCM/ctDNA samples were analyzed and 18 MRD recurrences (5 with and 13 without clinical progression) occurred after the end of treatment. Twelve samples were first detected by ctDNA, 3 by FCM, and 3 synchronously. In conclusion, time-limited MRD-guided acalabrutinib, venetoclax, and obinutuzumab achieved deep remissions in almost all patients with relapsed/refractory CLL. The addition of ctDNA-based analyses to FCM MRD assessment seems to improve early detection of relapses. This trial was registered at www.clinicaltrials.gov as #NCT03787264.

Innovations in conditioning and post-transplant maintenance in AML: genomically informed revelations on the graft-versus-leukemia effect.

Acute Myeloid Leukemia (AML) is the prototype of cancer genomics as it was the first published cancer genome. Large-scale next generation/massively parallel sequencing efforts have identified recurrent alterations that inform prognosis and have guided the development of targeted therapies. Despite changes in the frontline and relapsed standard of care stemming from the success of small molecules targeting FLT3, IDH1/2, and apoptotic pathways, allogeneic stem cell transplantation (alloHSCT) and the resulting graft-versus-leukemia (GVL) effect remains the only curative path for most patients. Advances in conditioning regimens, graft-vs-host disease prophylaxis, anti-infective agents, and supportive care have made this modality feasible, reducing transplant related mortality even among patients with advanced age or medical comorbidities. As such, relapse has emerged now as the most common cause of transplant failure. Relapse may occur after alloHSCT because residual disease clones persist after transplant, and develop immune escape from GVL, or such clones may proliferate rapidly early after alloHSCT, and outpace donor immune reconstitution, leading to relapse before any GVL effect could set in. To address this issue, genomically informed therapies are increasingly being incorporated into pre-transplant conditioning, or as post-transplant maintenance or pre-emptive therapy in the setting of mixed/falling donor chimerism or persistent detectable measurable residual disease (MRD). There is an urgent need to better understand how these emerging therapies modulate the two sides of the GVHD vs. GVL coin: 1) how molecularly or immunologically targeted therapies affect engraftment, GVHD potential, and function of the donor graft and 2) how these therapies affect the immunogenicity and sensitivity of leukemic clones to the GVL effect. By maximizing the synergistic action of molecularly targeted agents, immunomodulating agents, conventional chemotherapy, and the GVL effect, there is hope for improving outcomes for patients with this often-devastating disease.

Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3.

Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit. Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS. Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575). Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

Multi-gene measurable residual disease assessed by digital polymerase chain reaction has clinical and biological utility in acute myeloid leukemia patients receiving venetoclax/azacitidine.

Venetoclax with azacitidine (ven/aza) is a lower-intensity therapeutic regimen that has been shown to improve outcomes in elderly patients with acute myeloid leukemia (AML). Measurable residual disease (MRD) using flow cytometry is a valuable tool for the prediction of relapse in AML using conventional therapies and ven/aza; however, the prognostic value for broadscale molecular MRD after ven/aza treatment is less clear. We aimed to determine the utility of retrospective assessment using multi-gene molecular MRD by droplet digital polymerase chain reaction (ddPCR). We found this approach correlates with outcomes in a cohort of patients receiving frontline ven/aza for AML. The predictive value of ddPCR MRD persisted when NPM1 mutations were removed from analysis, as well as after adjustment for the impact of stem cell transplant on outcomes. Late achievement of MRD negativity, including after SCT, was still associated with superior outcomes compared to persistently detectable MRD. We further explored the impact of ven/aza on the burden of different classes of mutations, and identified the persistence of splicing factor mutations, commonly associated with MDS, as a consistent finding after ven/aza treatment. These data add to our understanding of the effects of ven/aza on AML disease biology and provide details on molecular depth of remission that can guide prospective trials in the future.

Chidamide-Based Pre-Emptive Treatment for High-Risk AML Patients after Hematopoietic Stem Cell Transplantation: A Real-World Experience from Chinese Single-Center

Background: The treatment of relapsed or refractory acute myeloid leukemia ( AML) remains challenging. Measurable residual disease (MRD) persistence at transplantation or post-transplantation has been identified as the strongest risk factor for relapse and poor outcomes for patients with hematological malignancies (HMs). Chidamide, a novel oral histone deacetylase inhibitor, has shown potential therapeutic effects in various types of HMs by inducing cell apoptosis and regulating immunity. This study aimed to evaluate the efficacy and safety of Chidamide-based prophylactic or pre-emptive treatment for patients who are MRD positive before or who have sustained MRD positive after transplantation. Aim: The rate of 6 months of conversion to MRD- and relapse-free survival of high-risk AML after Chidamide-based treatment. Methods: From December 2020 to July 2023, 50 patients with high-risk HMs received chidamide-based therapy after allo-HSCT. 39 patients were diagnosed with AML ( 4 secondary AML), 2 with myelodysplastic syndromes, 6 with acute lymphoid leukemia, and 3 with mixed-phenotype acute leukemia. 46 patients (92%) with relapsed/refractory status or detectable MRD (MRD+) at transplantation or after allo-HSCT received chidamide as pre-emptive, and the remaining 4 high-risk patients with MRD− conducted as prophylactic intervention. Patients with detectable MRD before transplantation and those who remained positive for MRD after transplantation were defined as very high-risk AML (VHR-AML). Chidamide was administered at a dose of 5 mg per day orally, 6 times per week, lasting at least 1 year after engraftment. Additional agents included hypomethylating agents (HMAs), donor lymphocyte infusion (DLI) or tyrosine kinase inhibitor (TKI) in patients with Philadelphia chromosome-positive. In this study, 28 patients received chidamide monotherapy, 13 received chidamide combined with HMAs, and 9 cases with other therapy. Results: The median age of all patients was 38 years old (range 17-67), comprising 24 males and 26 females. Up to 1st July 2023, with a median follow-up period of 376 days (25-984d), the overall rate of MRD negative showed 64%. The rate of MRD- survival, Relapse-free survival (RFS) and overall survival (OS) were 56%, 66% and 76%, respectively. The 6 months MRD negative rate, RFS and OS rate were 86%, 82%, 86% and 88%, which maintained at 82%, 82% and 86% with 12 months follow-up, respectively. In 46 cases of the pre-emptive intervention arm, the overall MRD- rate was 61.7%. Among them, 83.3% of patients (20/24) who received chidamide monotherapy exhibited a much higher conversion to MRD− than those combined with HMAs (7/13, 53.8%) or other drugs (2/9, 22.2%) (P=0.004). In 4 cases who received chidamide monotherapy as prophylactic intervention, 3 patients sustained MRD negativity up to the last follow-up, except for one patient diagnosed with MPAL(B+M) relapsed after 1 year of HSCT with taking chidamide for 6 months. A total of 30 patients (including 25 AML) with VHR diseases remained in a status of MRD+ or non-remission after transplantation. Eighteen patients (60%) achieved MRD− and sustained for a median of 251 days (range 31-531 d). VHR-AML patients account for 94.4% (17/18) of MRD- responders(Figure 1A). Similarly, the results showed a higher rate of conversion from MRD+ to MRD− in chidamide monotherapy than the combination groups (Chidamide monotherapy, 81.8%; Chidamide + HMA, 63.6% and Chidamide + others, 25%, P=0.042,Figure 1B). It highlighted that treatment with chidamide resulted in increased MRD− response, especially for AML. On the contrary, of 7 patients with B-cell malignancy, including 5 B-ALL and 2 MPAL (B + M) patients, only 2 (28.6%) patients converted to MRD−. Reversible grade 3/4 neutropenia occurred in 38% of patients, and thrombocytopenia was observed in 24% during the first four treatment cycles. Five patients experienced grade 1/2 non-hematological adverse events, such as fatigue, gastrointestinal reaction, pneumonia and infection. No new-onset GvHD was reported in patients without a prior history of GvHD during chidamide treatment. Conclusion: The chidamide-based regimen is safe and effective in pre-emptive treatment for patients with high-risk relapsed AML after transplantation. Whether as a monotherapy or combined with HMA, chidamide shows significant efficacy in eliminating MRD, warranting further clinical research.

Factors Underlying Impaired Organ Recovery Despite a Deep Hematologic Response in Patients with Systemic AL Amyloidosis

Background: Amyloid-mediated organ dysfunction is the main determinant of survival for patients with light chain (AL) amyloidosis. Reducing the production of amyloidogenic light chains with plasma cell-directed therapy is a prerequisite for organ response. Despite achieving a hematologic complete response (hemCR), some patients have enduring organ dysfunction. A better grasp of the mechanisms underlying organ recovery is needed, especially as attention moves to novel therapeutics that trigger removal of existing amyloid deposits, and as graded organ response criteria to gauge improvement more precisely than traditional binary systems are adopted. Aims: We designed this study to identify the (1) rates of organ non-response and (2) possible reasons for impaired organ recovery in patients with AL amyloidosis with hemCR after treatment. Methods: Patients with biopsy confirmed AL amyloidosis who presented to our center for post-treatment assessment between February 2019 and June 2023 were included if they had major organ involvement (heart, kidney and/or liver) and were evaluable for organ response (Palladini, 2012). Graded cardiac response was assessed by validated criteria (Muchtar, 2022). We excluded patients who received amyloid fibril-targeted antibody therapies. To eliminate the possibility of insufficient hematologic response as a confounder for organ non-response, we focused only on patients with hemCR. Organ response was measured as best response &amp;gt;3 months from hemCR achievement. Reasons for organ non-response were postulated by our multidisciplinary team after extensive workup and review of clinical data. Results: Among 143 patients with hemCR, the median age at diagnosis was 58 years (range 30-78); 94 (66%) were male; and 24 (17%) identified as non-white race. Kidney, heart and liver involvement was present in 117 (82%), 68 (48%) and 17 (12%) patients, respectively; 54 (38%) had ≥2 major organs affected. Final treatment granting hemCR was high-dose melphalan and stem cell transplantation for 49 (34%); bortezomib-based for 37 (26%); daratumumab monotherapy for 31 (22%); daratumumab-CyBorD for 18 (13%); and an immunomodulatory drug for 8 (6%) patients; 58 (41%) required ≥2 lines of therapy to achieve hemCR. Failure to attain organ response was observed in 40/117 (34%), 19/68 (28%) and 3/17 (18%) of patients with kidney, heart and liver involvement, respectively. Of 42 patients with both kidney and heart involvement, 21 (50%) had concordant responses of both organs; 6 (14%) had concordant non-responses; and 15 (36%) had discordant responses. Among 49 heart responders, 14 (29%) attained CarCR (nadir BNP ≤80 pg/mL); 16 (33%) CarVGPR (&amp;gt;60% reduction); and 19 (39%) CarPR (31-60% reduction); 40/77 (52%) kidney responders attained proteinuria &amp;lt;500 mg/24h. Clinical features of organ non-responders in relation to responders are reported in Table 1. Notably, kidney non-responders had more advanced disease at baseline, whereas heart non-responders more often had lambda-typic amyloidogenic light chains. Among kidney non-responders, 2 had stable and another 2 had rising proteinuria level; the remaining 36 had improved proteinuria but were categorized as non-response due to &amp;gt;25% worsening of eGFR. Among heart non-responders, 5 had stable elevation of BNP and 14 experienced organ progression (BNP increase &amp;gt;30% and &amp;gt;50 pg/mL); 2 required heart transplantation. The two most common factors believed to underlie kidney non-response were permanent kidney damage at diagnosis needing dialysis and treatment-related toxicity (Table 2). For 10 (25%) kidney non-responders, there was no apparent explanation, 7 of whom had detectable measurable residual disease (MRD) by multiparametric flow cytometry. Most cases of heart non-response had no apparent explanation; 6 of these 8 patients had detectable MRD. Conclusions: Despite effective treatment of the plasma cell clone, a considerable number of patients with AL amyloidosis in hemCR have enduring organ dysfunction. We found that the reasons for organ non-response differed across organ systems. Response was not always concordant for all involved organs, suggesting heterogeneity in organ biology in terms of mechanisms for amyloid-mediated injury and intrinsic ability to repair. Careful scrutiny of reasons for organ non-response is warranted before providing further hematologic treatments, which may be ineffective for organ recovery.

Molecular Measurable Residual Disease in Patients with Newly Diagnosed m IDH1 Acute Myeloid Leukemia Treated with Ivosidenib + Azacitidine

Background: Ivosidenib (IVO) + azacitidine (AZA) improved complete remission (CR) rates and overall survival (OS) relative to placebo (PBO) + AZA in patients (pts) with newly diagnosed mutant isocitrate dehydrogenase 1 (m IDH1) acute myeloid leukemia (AML) in the pivotal AGILE study (Montesinos et al. NEJM 2022). Prior analyses showed clinical responses to IVO+AZA were associated with deep clearance of m IDH1 (limit of detection [LOD]: 0.02-0.04% variant allele frequency [VAF]), as well as clearance of baseline co-mutations below the threshold of conventional next-generation sequencing (NGS) (LOD: 2.0% VAF) (Döhner et al. Blood 2022; Daigle et al. Blood 2021). Measurable residual disease (MRD), a negative prognostic marker, following chemotherapy is often detected via multiparametric flow cytometry or quantitative polymerase chain reaction although both techniques have their limitations. (Heuser et al. Blood 2021). NGS can detect a wide range of AML mutations and studies show that NGS-assessed MRD is highly predictive of both relapse and survival (Thol et al. Blood 2018; Tsai et al. Blood Adv 2021). However, a limitation of NGS is difficulty in distinguishing between somatic leukemia-associated mutations and clonal hematopoiesis of indeterminate potential (CHIP) (Bacher et al. Blood Cancer J 2018). We aimed to perform an NGS analysis of MRD responses in the AGILE study. Methods: All AGILE pts who had a best overall response (BOR) of CR, CR with incomplete count recovery, or CR with incomplete platelet recovery, and had ≥1 on-treatment bone marrow mononuclear cell (BMMC) sample available were included. Suggested timepoints for MRD testing included day 1 of treatment cycles 3, 5, 7, 9, 11, 14, 20, 26, and 32. Baseline and on-treatment BMMC DNA samples were analyzed using a diagnostic 51-gene myeloid NGS panel (LOD: 3% VAF) and a 26-gene AML MRD panel, respectively. For variants detected at baseline, the LOD was 0.1% VAF; for variants not detected at baseline (either emerging mutations or if baseline samples were unavailable), the LOD was 0.5% VAF. All variants above the applicable LOD with known or potential clinical significance were considered evidence of positive MRD, aside from DNMT3A, TET2 and ASXL1 (“DTA”) mutations to reduce the risk of false-positive MRD due to CHIP. Results: The analysis set comprised 173 samples from 33 IVO+AZA-treated pts and 10 PBO+AZA-treated pts (Fig. 1). Clinical response data were based on a March 18, 2021 primary analysis data cut; OS data were based on an updated June 30, 2022 data cut. The median number of baseline mutations was 4 (range: 1-10) per patient, median number of MRD assessments was 3 (range: 1-9) and median follow-up period was 189 days (range: 49-875). Ten (30.3%) IVO+AZA-treated pts became MRD-negative (MRD neg), compared with 2 (20.0%) PBO+AZA-treated pts. All pts attaining an MRD neg response had a BOR of CR (10 [34.5%] of 29 IVO+AZA-treated pts in CR; 2 [22.2%] of 9 PBO+AZA-treated pts in CR). Seven (70.0%) of the 10 MRD neg IVO+AZA-treated responding pts converted to an MRD neg response by day 1 of cycle 7 (C7D1). Fewer pts with an MRD neg response had an Adverse risk at baseline according to European LeukemiaNet 2022 genetic risk classification versus those pts with an MRD-positive (MRD pos) response (26.3% vs 73.7%) (Table 1). In the IVO+AZA arm, rates of event-free survival at 12 months and OS at 24 months were numerically higher in MRD neg vs MRD pos responders (80.0% vs 60.6% and 88.9% vs 72.3%, respectively) but did not reach statistical significance. All 5 (15.2%) IVO+AZA-treated pts with confirmed relapses had detectable MRD at the last completed assessment prior to relapse. One pt converted from an MRD neg to an MRD pos response (“MRD relapse”) 169 days prior to overt clinical relapse. Among the 23 IVO+AZA-treated pts without an MRD neg response, 16 were alive as of the updated data cut; OS duration ranged from 20.3-48.9 months. Conclusions: IVO+AZA induced molecular MRD negativity in approximately one third of responding pts with newly diagnosed m IDH1 AML; MRD neg responses were most often observed on or before C7D1. Interestingly, several pts had durable clinical responses and OS despite ongoing MRD positivity, potentially due to persistent CHIP rather than true MRD, illustrating the complexity of interpreting NGS MRD data. Additional analyses, including associations between specific molecular alterations, MRD response, and OS are ongoing and will be presented.

Prospective Evaluation of Measurable Residual Disease (MRD) and Sustainability of the Response in Patients with Systemic AL Amyloidosis Treated with Daratumumab

Background: Daratumumab can provide deep hematologic responses for patients with light chain (AL) amyloidosis, both through its direct anti-clonal activity and immunomodulatory effects on other cell populations in the bone marrow (BM) microenvironment. Promising efficacy in the frontline setting when combined with CyBorD (per the ANDROMEDA trial), as well as in the relapsed/refractory setting as monotherapy, has led to daratumumab becoming the first FDA-approved therapy for AL amyloidosis. Though it is administered for up to 24 cycles, the optimal duration of treatment is unclear. Dynamic monitoring of measurable residual disease (MRD) may provide insights into changes in the aberrant plasma cell (PC) clone and sustainability of the hematologic response in relation to daratumumab therapy. Aims: We sought to evaluate the rates of MRD clearance and resurgence both during and after daratumumab therapy for AL amyloidosis. Methods: MRD status was assessed for patients followed at the Boston University Amyloidosis Center, who were treated with a daratumumab-based regimen and achieved a hematologic very good partial response (hemVGPR) or complete response (hemCR) according to consensus criteria (Palladini, 2012). MRD assessments were performed by multiparametric 10-color flow cytometry of BM aspirates (sensitivity level of ≤10 -5) and repeated at 12-month intervals during follow-up. Clonal progression was defined as growth in the aberrant PC clone size of &amp;gt;1-log. Results: Between 2019 and 2023, a total of 66 patients achieved ≥hemVGPR and were tested for MRD; 43 (65%) received daratumumab monotherapy in the relapsed/refractory setting and 23 (35%) in combination with CyBorD as frontline therapy. Collectively, 48 (73%) achieved a hemCR and 18 (27%) a hemVGPR. The median age at diagnosis was 60 years (range 35-78); 19 (29%) patients were female; and 11 (17%) identified as non-white race. MRD assessment was performed once, twice or ≥3 times for 33, 18 and 15 patients, respectively. The first MRD evaluation occurred while still receiving daratumumab for 33 patients (at median 12 cycles, range 6-23); the remaining patients had their first MRD evaluation after therapy completion (median one month after, range 0-25). Of the entire cohort, 28 (42%) patients achieved MRD negativity and 38 (58%) MRD positivity (median estimated aberrant PC clone size 1.5 x 10 -4, range 1.4 x 10 -5 to 1.1 x 10 -2, representing 46.9% ± 32.8% of total PCs) at first evaluation. All but one patient with a hemVGPR had detectable MRD. Of the 23 patients who received frontline daratumumab-CyBorD (18 hemCR and 5 hemVGPR), 8 (35%) achieved MRD negativity at first evaluation; whereas 20 (47%) of the 43 patients who received daratumumab as monotherapy (30 hemCR and 13 hemVGPR) achieved MRD negativity. We surveyed MRD profiles based on the number of daratumumab treatment cycles received (Table 1) and found no apparent patterns with increasing cycles. Serial MRD monitoring was performed for 33 patients (Figure 1). Of 10 patients who continued to receive daratumumab between MRD assessments (group 1), 6 had sustained MRD negativity; 2 had persistent MRD positivity (of whom one had clonal progression); and 2 had MRD clearance (conversion from positive to negative). Of 23 patients who underwent serial MRD assessments after completing daratumumab (group 2), 9 (39%) had sustained MRD negativity; 10 (43%) had persistent MRD positivity; 2 (9%) had MRD clearance; and 2 (9%) had MRD resurgence (conversion from negative to positive), which occurred 17 and 26 months after daratumumab cessation. Clonal progression was observed in 5 of the 10 patients with persistent positivity, of whom 3 experienced a hematologic relapse. Conclusions: Our findings show that patients with AL amyloidosis can attain deep responses with daratumumab-based treatments, even to the depth of undetectable MRD. Clearance of MRD was frequent not only during treatment with daratumumab but also after completion of therapy, suggesting continuing effects on the plasma cell clone. Clonal progression after daratumumab completion was often associated with hematologic relapse. Prospective studies are needed to investigate whether daratumumab may be stopped early for those with undetectable MRD, or whether those with persistent detectable disease may benefit from extending daratumumab treatment beyond 24 cycles.

Role of Measurable Residual Disease (MRD) Testing for the Prediction of Late Relapses Following Allogeneic Hematopoietic Cell Transplantation in Adult Acute Myeloid Leukemia

BACKGROUND: Measurable residual disease (MRD) before and/or shortly after allogeneic hematopoietic cell transplantation (HCT) is an independent indicator of high post-HCT relapse risk in acute myeloid leukemia (AML). However, many relapses, particularly among patients with MRD, occur within the first 3 months after allografting, and the role of MRD testing in the identification of patients at risk of relapses occurring at later times is unknown. METHODS: To address this uncertainty, we studied all adults ≥18 years with AML or MDS/AML based on 2022 International Consensus Classification criteria who received a first allograft while in first or second morphologic remission at a single institution between 4/2006 and 3/2023 and underwent MRD testing via multiparameter flow cytometry during the pre-HCT evaluation. In line with the performance characteristics of the assay, any detectable MRD was considered positive. RESULTS: One thousand two hundred and sixty-two patients with AML (n=1,112 [88%]) or MDS/AML (n=150 [12%])underwent allograft following myeloablative (n=732 [58%]) or non-myeloablative (n=530 [42%]) conditioning regimens. Of these, 260 (21%) tested positive for MRD during the pre-HCT evaluation. With a median follow-up of 60.6 (range: 1.9-196.3) months after HCT among survivors, there were 589 deaths, 381 relapses, and 259 NRM events contributing to the probability estimates for relapse, overall survival (OS), relapse-free survival (RFS), and non-relapse mortality (NRM) in this cohort. 239/1,262 patients (19%) experienced disease recurrence (n=181 [14%]) and/or death (n=89 [7%]) within the first 100 days after allografting. Relapse ( P&amp;lt;0.001) and death ( P=0.002) but not NRM ( P=0.29) before day +100 were more common among patients with pre-HCT MRD. Of patients alive without relapse at day +100, 93% (954 of 1,023) underwent bone marrow restaging studies between day 70 and 100 post-HCT. Among these 954 patients, 146 (15%) had MRD before HCT, whereas only 25 (3%) had MRD at day +70-100 testing. The latter had a significantly higher 3-year relapse risk (37% vs. 18%; P=0.002), and worse RFS (17% vs. 68%; P&amp;lt;0.001) OS (16% vs. 72%; P&amp;lt;0.001) and NRM (46% vs. 14%; P&amp;lt;0.001) relative to the 929 patients without MRD; for results of univariate regression models, see Table 1. Importantly, however, while 130 of the 146 patients (89%) with MRD before HCT tested negative for MRD at day +70-100, their outcomes were substantially worse compared to patients who tested negative for MRD before HCT and at day +70-100, with 3-year relapse risk of 38% vs. 15% ( P&amp;lt;0.001), 3-year RFS of 47% vs. 71% ( P&amp;lt;0.001), and 3-year OS of 53% vs. 75% ( P&amp;lt;0.001), whereas 3-year NRM estimates were similar (14% vs. 14% ( P=0.21). Qualitatively similar results were obtained when the cohort was restricted to patients with AML, and also when comparing patients undergoing myeloablative conditioning with those undergoing non-myeloablative conditioning, with a statistically significantly higher relapse risk and lower RFS and OS but not NRM for patients with MRD before HCT but no MRD at day +70-100 compared to those who tested negative for MRD before HCT and at day +70-100 (Table 1). CONCLUSION: For AML and MDS/AML patients alive without relapse at day +100 after allografting, MRD testing at day +70-100 post-HCT identifies patients at increased risk of relapse and worse survival, but only a small number of patients will test positive at this post-HCT timepoint. While a high proportion of patients with MRD before HCT will test negative for MRD at day +70-100, their outcomes are substantially inferior to patients without MRD both before and at day +70-100 after HCT. These data suggest that all patients with pre-HCT MRD should be considered for pre-emptive therapeutic strategies, ideally in the setting of well-controlled clinical trials, given their high risk of disease recurrence regardless of the post-HCT MRD information.

Association of Measurable Residual Disease with Progression-Free Survival in Patients with Chronic Lymphocytic Leukemia: A Systematic Review and Meta-Analysis in the Era of Novel Agents

Introduction: Achieving undetectable measurable residual disease (uMRD) following treatment has shown significant prognostic value in several hematological malignancies. In chronic lymphocytic leukemia (CLL), uMRD is associated with improved outcomes in the era of chemoimmunotherapy (CIT). However, the role of measurable residual disease (MRD) in the context of novel agents such as Bruton tyrosine kinase inhibitors (BTKi) and/or BCL2 inhibitors (e.g. venetoclax) is uncertain. To address this question, we conducted a systematic review of the literature and performed a comprehensive meta-analysis of trials that included novel agents to evaluate the association between MRD status after treatment and PFS in patients with CLL. Methods: We conducted a comprehensive search of PubMed, EMBASE, Scopus, and Web of Science focusing on CLL trials reporting MRD and its association with PFS. Results were independently screened by two reviewers. Inclusion criteria included prospective phase 3 trials involving a novel agent in one of the treatment arms, while studies with incomplete information on MRD status related to PFS, reviews, abstracts, and retrospective analyses were excluded. The initial search identified 185 studies in PubMed and 402 studies in EMBASE. After applying prespecified criteria, a total of 10 phase 3 trials were included in our analysis. We extracted sample size, patient age, follow-up time, time point and tissue of MRD assessment, MRD cut-off and rate, performance status and molecular status when available. We only considered treatment arms with complete MRD information. The comparison involved patients who achieved uMRD with those exhibiting detectable MRD. When available, hazard ratios (HR) and confidence intervals (CI) were used to evaluate the relationship between MRD status and PFS. If not, we used Kaplan-Meier (KM) curves from both uMRD and MRD subgroups and extracted the coordinates points of the curves using DigitizeIt software (version 2.5.10, I. Bormann) and using the number at risk provided we estimated the HRs and CIs. A meta-analysis was performed using a random effects model from the R package metafor (Viechtbauer, W. (2010). Conducting meta-analyses in R with the metafor package. Journal of Statistical Software, 36(3), 1-48). The pooled hazard ratio estimates, and the corresponding 95% CI and prediction intervals (PI) were reported. Funnel and Baujat plots were generated to assess study heterogeneity and bias. All analysis was performed using R version 4.1.2 (R Foundation for Statistical Computing, Vienna, Austria). Results: A total of 10 phase 3 trials, encompassing 14 treatment arms and involving 3152 patients, met the stringent inclusion criteria. All but one study used a uMRD cut-off of &amp;lt; 0.01%. Detailed information on the treatment arms and key trial characteristics is presented in Table 1. Notably, ten treatment arms were derived from first-line treatment trials, while the remaining arms pertained to the relapsed/refractory population. Only two trials (4 treatment arms) assessed MRD using next generation sequencing (NGS), while the rest used multicolor flow cytometry (MFC) (9 treatment arms) and allele-specific oligonucleotides polymerase chain reaction (ASO-PCR) (2 treatment arms). All but 3 trials assessed MRD in both bone marrow (BM) and peripheral blood (PB). One trial (2 treatment arms) was excluded from the met-analysis due to higher MRD cut-off. All studies included in the meta-analysis measured uMRD (&amp;lt;0.01) versus MRD. The PFS pooled HR estimate for achieving uMRD at 0.01 cut off from the meta-analysis was 0.32 (95% CI [0.22, 0.45]), with minimal bias observed on the Funnel Plot. Conclusions: In this comprehensive meta-analysis, comprising 9 phase 3 trials, achieving uMRD was strongly associated with PFS. These findings further establish the prognostic role of MRD in CLL management and its potential use as a surrogate marker in clinical trials. As the body of evidence on MRD in CLL continues to grow, it becomes imperative to standardize the optimal time point, methodology, and tissue for MRD assessment. Substantial heterogeneity in these aspects underscores the necessity for unified guidelines to ensure the accurate and consistent evaluation of MRD status in clinical practice.

Comparison of Autologous, Matched Sibling, and Alternative Donor Stem Cell Transplant Outcomes for Acute Myeloid Leukemia Patients in First Remission: A Propensity Score Matching Study

Introduction Autologous hematopoietic stem cell transplantation (auto-HSCT), matched sibling donor HSCT (MSD-HSCT), and alternative donor HSCT (AD-HSCT) are viable post-remission treatment options for acute myeloid leukemia (AML). Auto-HSCT is more commonly administered in favorable- and intermediate-risk AML with good remission, while MSD-HSCT and AD-HSCT are suggested for patients with high-risk factors. In the present study, we aim to retrospectively compared auto-HSCT with MSD-HSCT and AD-HSCT in de novo AML patients who are in first complete remission (CR1) with favorable or intermediate risk, according to 2022 ELN criteria. Methods We conducted a single-center retrospective comparative analysis, comparing auto-HSCT and allo-HSCT for favorable and intermediate-risk de novo AML in CR1. Patients with secondary AML, acute promyelocytic leukemia, poor-risk AML, those receiving syngeneic HSCT, those not in CR1 before HSCT, or those who achieved CR1 with ≥ 3 cycles of induction chemotherapy were excluded from the study. A total of 283 de novo favorable- and intermediate-risk AML patients, based on the ELN 2022 criteria, in first complete remission were initially included for propensity score matching. Persistent undetectable MRD (uMRD) was defined as uMRD after one course of chemotherapy without recurrent positive MRD before HSCT, while non-persistent uMRD was characterized by the presence of detectable MRD at least once before HSCT. The variables used for propensity score matching included induction chemotherapy cycles, consolidation chemotherapy cycles, and measurable residual disease (MRD) measurement by flow cytometer before HSCT. A caliper width of 0.2 was used. Following the matching process, 126 patients were selected for further analysis, with 42 patients in each of the auto-HSCT, MSD-HSCT, and AD-HSCT groups. Results After applying propensity score matching, a final cohort of 126 patients was available for analysis. This cohort consisted of 42 patients in each group: auto-HSCT, MSD-HSCT, and AD-HSCT. Among the AD-HSCT group, 38 of 42 (90.5%) patients received haploidentical HSCT (haplo-HSCT). All patients received myeloablative conditioning regimen. There were no significant differences observed in the 3-year overall survival (OS) and disease-free survival (DFS) among the auto-HSCT, MSD-HSCT, and AD-HSCT groups [3-year OS: 79.5% (95% CI, 67.8-93.3%), 83.0% (95% CI, 72.2-95.3%), and 65.7% (95% CI, 50.5-85.5%), respectively; P=0.21. 3-year DFS: 72.6% (95% CI, 59.9-87.9%), 83.0% (95% CI, 72.2-95.3%), and 67.5% (95% CI, 54.2-84.1%), respectively; P=0.32]. The cumulative incidence of 3-year NRM was 2.7% (95% CI, 2.0-12.5%), 7.3% (95% CI, 1.8-17.9%), and 21.9% (95% CI, 10.7-35.6%), respectively (P=0.008). The 1-year probability of OS after relapse was higher in the auto-HSCT group (44.4%; 95% CI, 21.4-92.3%) compared with MSD-HSCT (0.0%) and AD-HSCT (37.5%; 95% CI, 8.4-99.9%) (P=0.0017). The MRD status before HSCT had an impact on DFS (persistent uMRD versus non-persistent uMRD: HR=0.29; 95% CI 0.09-0.94, P=0.04) and relapse (persistent uMRD versus non-persistent uMRD: HR=0.17; 95% CI 0.05-0.66, P=0.01) following auto-HSCT. The subgroup analysis was then performed based on MRD status before HSCT. In patients with uMRD before transplant (n=83), OS was similar across the groups. However, auto-HSCT showed a trend of increased DFS compared to AD-HSCT (HR 2.85, P=0.09), resulting in a 3-year DFS and OS of 79.1% and 82.8%, respectively. In the non-persistent uMRD group (n=38), auto-HSCT exhibited a tendency to increase the risk of relapse, particularly when compared to AD-HSCT (HR 0.24, P=0.07), but this did not result in inferior OS. The monthly direct medical cost per patient within the first two years after HSCT was significantly lower in auto-HSCT compared to MSD-HSCT (P=0.015) and AD-HSCT (P&amp;lt;0.001). Conclusions Our results provide evidence for the use of auto-HSCT as a viable therapeutic option for favorable- and intermediate-risk de novo AML patients in first complete remission with persistent uMRD. Additionally, our findings demonstrated a notable cost advantage associated with auto-HSCT compared to MSD-HSCT and AD-HSCT.

Post-Hoc Analysis of Measurable Residual Disease from BMT-CTN 1506/Morpho: FLT3-ITD Variant Allele Frequency and Survival Are Highly Correlated

Background: BMT CTN 1506/MORPHO was a randomized study of the FLT3 inhibitor gilteritinib versus placebo as post-transplant (HCT) maintenance therapy for patients (pts) with FLT3-ITD acute myeloid leukemia (AML). Patients with FLT3-ITD AML in first remission underwent HCT and then were randomized, in double-blind fashion, to either gilteritinib or placebo for 24 months. The primary endpoint was relapse-free survival (RFS), and a pre-specified secondary endpoint was the effect of measurable residual disease (MRD) on survival as detected by a highly sensitive assay for FLT3-ITD mutations. In the primary analysis, while RFS was higher for pts randomized to gilteritinib, the difference did not reach the pre-determined threshold for significance (HR: 0.679; 95% CI: 0.459, 1.005; 2-sided p-value: 0.0518). However, in the secondary analysis, the 50.6% of pts who had MRD detectable pre- or post-HCT had significantly higher RFS with gilteritinib (HR of relapse or death=0.515, 95% CI: 0.316, 0.838, p = 0.0065). In this post-hoc analysis, we examined 1) the impact on RFS of different levels of FLT3-ITD variant allele frequency (VAF) pre-randomization (immediately before or after HCT but prior to randomization to gilteritinib or placebo); 2) the impact of the presence of multiple mutations detected as MRD pre-HCT; and 3) the eradication of FLT3-ITD clones detected post-HCT during follow up on gilteritinib or placebo. Methods: First-pull marrow aspirates were collected from pts at two time points pre-randomization (pre-HCT and between 30-90 days post-HCT), as well as at 3, 6, 12, 18, and 24 months post-randomization. For MRD detection (performed at Invivoscribe; San Diego, CA), 700 ng input DNA was amplified by polymerase chain-reaction (PCR) using 25 cycles and primers flanking exons 14 and 15 of FLT3, followed by next-generation sequencing (NGS) analysis of the amplicons. Variant allele frequency (VAF) was calculated as FLT3 mutant reads/total FLT3 reads. For pts with multiple FLT3-ITD mutations, the VAF used in analysis was the sum of the VAFs for each FLT3-ITD variant. The lower limit of blank (LOB) of the assay is estimated to be 1 x 10 -6 VAF. For terminology, VAF &amp;gt; 1 x 10 -6 and &amp;lt; 1 x 10 -5 is referred to as MRD6, VAF &amp;gt; 1 x 10 -5 and &amp;lt; 1 x 10 -4 is MRD5, VAF &amp;gt; 1 x 10 -4 or greater is MRD4, and MRD0 equals no detectable MRD. Results: MRD was evaluated in 350/356 (98.3%) pts pre-HCT and 347/356 (97.5%) pts post-HCT. MRD was detected in 46% of pts pre-HCT and 19.9% prior to randomization, including 4.5% who did not have detectable MRD pre-HCT. The variant allele frequency (VAF) of detectable MRD ranged from a low of 1.09 x 10 -6 to a high of 3.0 x 10 -1. More than a single mutation was detected in 51 pts pre-HCT. Most of these 51 pts had 2 clones, but the total ranged from 2-9. The presence of more than one mutation detected as MRD immediately pre-HCT was associated with worse RFS compared with all other pts (MRD-positive with only one clone and MRD-negative), irrespective of treatment arm (Figure 1A; HR=2.428, 95% CI: 1.555, 3.792, P &amp;lt; 0.001). There was no significant difference in age, mutation length, VAF, or karyotype between pts with more than one mutation and those with single mutations. However, if the VAFs of pts with multiple FLT3-ITD mutations were summed and treated as a single value, then the median VAF for pts with multiple mutations was higher than for those with single mutations (2.14 x 10 -4 vs. 3.12 x 10 -5). The VAF (including the summed VAFs of pts with multiple mutations) at multiple levels correlated very closely with RFS after HCT. To illustrate this quantitative effect of peri-HCT FLT3-ITD VAF on RFS, Kaplan-Meier analysis of pts on the placebo arm grouped by MRD level is displayed in Figure 1B. In the 71 pts with MRD detectable post-HCT, the MRD was eradicated in 69% of pts on gilteritinib versus 44% of pts on placebo. Conclusions Pts with multiple FLT3-ITD mutations have a worse prognosis, which may simply be a reflection of increased disease burden (VAF). The quantity of FLT3-ITD MRD appears to highly correlate with outcome. Gilteritinib appears to augment the effect of HCT, as evidenced by increased eradication of MRD post-HCT. These data illustrate the potential utility of the PCR-NGS FLT3-ITD MRD assay in the management of pts with FLT3-ITD AML.

End-of-Treatment Response Assessment after Frontline Therapy for Aggressive B-Cell Lymphoma: Landmark Comparison of a Singular PET/CT Scan Versus Ultrasensitive Circulating Tumor DNA

Background : Lymphoma response criteria rely on PET/CT scans at end of therapy (EOT) to determine complete response (CR), which is necessary for cure. ~25% of patients achieve &amp;lt;CR by response criteria, but PET/CT scans have imperfect specificity and the positive predictive value of a single PET/CT scan at EOT is only ~50% (Kostakoglu 2021). To overcome this limitation, clinicians use additional tests including tissue biopsies or repeat PET/CT scans prior to salvage therapy to adjudicate positive results, but it remains unclear how often this occurs. Circulating tumor DNA (ctDNA) has improved tumor specificity that may reduce reliance on additional tests. We addressed these questions within a clinical trial delivering 1L therapy to pts with aggressive B-cell lymphoma. Methods : Pts were enrolled in a phase 2 study of DA-EPOCH-R or R-CHOP +/- acalabrutinib for treatment naïve DLBCL or high-grade B-cell lymphoma (HGBCL) [NCT04002947]. All pts were &amp;gt;18yrs old, stage II-IV, with adequate organ function. Pts completing induction therapy with available EOT PET/CT scans and EOT plasma samples were studied. PET/CT scans were interpreted by 2 nuclear medicine (NM) radiologists blinded to clinical outcomes using the 5-point Deauville Score (DS) with DS4/5 considered positive. Tissue biopsies and unplanned PET scans after the EOT PET/CT scan to determine remission status were recorded. Measurable residual disease (MRD) in plasma cfDNA was evaluated by Phased Variant Enrichment &amp; Detection Sequencing (PhasED-Seq) at Foresight Diagnostics blinded to clinical outcomes. Tumor derived Phased Variants (PVs) were identified from baseline pretreatment plasma samples or baseline tumor tissue, with matched constitutional DNA from paired PBMCs used to censor germline variants and CHIP. PVs were used to assess EOT MRD. Results were reported as MRD positive when ctDNA levels exceeded an analytical detection threshold (~1:10 6 cfDNA molecules) corresponding to 98% specificity. The prognostic utility of MRD was compared to standardized PET/CT scan at EOT to freedom-from-progression (FFP) and progression-free survival (PFS). Results : 55 enrolled pts completing planned therapy had EOT PET/CT and MRD analyzed. 54 (98%) pts were successfully genotyped and comprised the study population. Median age was 61 (range 26-85), including 22 (41%) female, 44 (81%) with advanced stage, and 26 (48%) with IPI score ³3. Pathologic subtypes included 24 (44%) GCB, 21 (39%) non-GCB, 8 (15%) HGBL-DH, and 1 (2%) THRLBCL. 43 (80%) pts received DA-EPOCH-R and 11 (20%) pts received R-CHOP. Twenty-six (48%) pts received acalabrutinib with R-chemotherapy. After 26 months median follow-up, the 2-year FFP and PFS of the cohort was 89% and 84%. Fourteen (26%) pts had a positive EOT PET/CT scan and 40 (74%) were negative. The concordance rate between the 2 NM radiologists on positive scans was 100%. Only 2 of 14 patients with a positive EOT PET/CT had clinical progression requiring salvage therapy (14% PPV). Nine (64%) of these pts required additional tests to determine remission status including 5 repeat PET/CT scans and 4 tissue biopsies. The 2-year PFS for pts with a positive vs negative EOT PET/CT was 66% vs 90% (p=0.08, Fig.A). Twelve (22%) pts had detectable EOT MRD and 42 (78%) were undetectable. 7 pts with detectable EOT MRD had clinical progression requiring salvage therapy or have died. While no pt with undetectable EOT MRD progressed, 1 (2%) died in remission of sudden cardiac death. Of 14 pts with positive EOT PET/CT, 7 (50%) had undetectable ctDNA and none progressed, suggesting MRD testing could have potentially rendered additional tests unnecessary. Conversely, patients with positive PET/CTs who progressed invariably had detectable ctDNA at EOT, suggesting utility of MRD for adjudicating PET/CT results. The 2-yr PFS for pts with detectable vs undetectable EOT MRD was 33% vs 98% (p&amp;lt;0.0001, Fig.B). At EOT, the PFS hazard ratio for MRD was 35.7, as compared with 3.1 for PET/CT. Conclusions : Response evaluations relying on PET/CT scans often require additional tests and procedures to assess remission status in aggressive B-cell lymphomas. Initiation of salvage therapy without adjudication in patients not achieving CR by EOT PET/CT scans will result in overtreatment. Given the higher specificity and PPV of EOT MRD, we propose an integrated response evaluation strategy combining these methods to reduce unnecessary additional tests and overtreatment.

Using Peripheral Blood (PB) Measurable Residual Disease (MRD) Levels to Predict &amp;lt;0.01% Bone Marrow Disease (BM uMRD4): Identification of Effective PB Targets for CLL Treatment Cessation in the Ibrutinib+Venetoclax Arm of the FLAIR Trial

CONCLUSIONS Time-limited treatments for CLL are under investigation but the optimal target for treatment cessation is not fully clear. Bone marrow (BM) measurable residual disease (MRD) is usually the most sensitive measure but would be too invasive to guide treatment in a routine setting. The iwCLL threshold of BM uMRD4 (&amp;lt;0.01%) has been demonstrated to be a powerful indicator of improved outcomes across multiple different trials and the aim of this analysis is to determine the feasibility of using PB MRD analysis to identify patients who have attained BM uMRD4. FLAIR (ISRCTN01844152) is an open-label, randomised, controlled, phase 3 trial comparing ibrutinib plus rituximab (IR) with fludarabine, cyclophosphamide and rituximab (FCR), subsequently amended to compare ibrutinib plus venetoclax (I+V) and ibrutinib alone (I) with FCR. Paired PB &amp; BM samples were scheduled at: (1) response assessment 9 months after randomization in all arms (n=1086); (2) end of treatment after 72 months in the ibrutinib-containing arms (n=137, most I/I+V participants have not reached this timepoint yet); and (3) confirmation of BM uMRD4 for initiation of planned stopping rules in participants with sustained PB uMRD4 defined as &amp;lt;0.01% PB MRD at 3 timepoints over 6 months (n=188 in the I+V arm). MRD analysis was performed using an ERIC-compliant 8-colour flow cytometry assay targeting acquisition of 2.2 million events (detection limit MRD5/0.001%). As the target could not always be met due to sample/laboratory limitations, stringent uMRD4 assessing 500 thousand leucocytes (detection limit 0.005%) was also evaluated. Table 1 shows the BM vs. PB MRD levels for different treatment arms and timepoints. The greatest discrepancy was observed in participants receiving FCR with a median 0.8log higher disease in the BM vs. PB. Participants receiving ibrutinib monotherapy had similar PB and BM MRD levels while the addition of either rituximab or venetoclax was associated with slightly higher (median &amp;lt;0.1 log) BM vs. PB MRD levels for both IR and I+V arms. The difference did not persist in the IR arm but remained during I+V treatment in some cases, with median &amp;gt;0.59 log higher BM vs. PB MRD levels in 29/182 participants achieving PB uMRD4 but with detectable BM MRD. Table 1 also shows the proportion of cases that attain BM uMRD4 according to different PB MRD thresholds. For participants with rituximab exposure in the past 3 months, BM uMRD4 was attained in 75-88% of participants with PB uMRD5, and only 43-76% of participants with stringent uMRD4. For participants with PB dMRD5 (0.001-0.01% MRD), only 14-52% achieved BM uMRD4. However, participants on I+V with either PB uMRD5 or stringent uMRD4 attained BM uMRD4 in 94-96% of cases. Planned cessation of treatment in the FLAIR trial was guided by sustained PB uMRD4, defined as 3 successive results with &amp;lt;0.01% PB disease over six months with confirmation of BM uMRD4 at the final time point. This strategy in the I+V arm is highly effective in achieving improved progression-free and overall survival compared to FCR [see related abstract]. Sustained PB uMRD4 led to BM assessments in 188 participants of which 173/188 (92%) attained BM uMRD4. High sensitivity PB MRD gave concordant results to BM MRD4 analysis in 91% of participants (172/188), while 9/188 (5%) had PB dMRD5 / BM uMRD4 (7/9 had detectable BM MRD in the range 0.002-0.007% and 2/9 had BM uMRD5/&amp;lt;0.001%) and 7/188 (4%) had PB uMRD5/stringent uMRD4 but with persistent BM dMRD4 (median 0.02% BM MRD, range 0.01-0.055%). PB MRD level correlates closely with BM MRD level but there is lower concordance at the 0.01%/MRD4 threshold after recent cessation of therapeutic antibody. PB uMRD4 is not a suitable target for treatment cessation as the majority of patients with 0.001%-0.01% PB MRD have &amp;gt;0.01% BM disease. For the identification of people attaining BM uMRD4 (&amp;lt;0.01%) on I+V treatment, sustained PB uMRD4 was &amp;gt;90% effective. For translation into MRD-guided treatment in future routine clinical practice, BM assessment may be replaced with PB MRD monitoring if the 0.001%/MRD5 threshold is applied.

Lenalidomide Consolidation Improves Measurable Residual Disease (MRD) Rates and Progression Free Survival in Patients with Chronic Lymphocytic Leukemia Following Initial FCR Chemotherapy - Final Analysis of CLL6 Residuum Study of the Australian Leukaemia and Lymphoma Group (ALLG) and the French Innovative Leukemia Organization (FILO)

Introduction Eradication of MRD after first line chemoimmunotherapy (CIT) correlates with longer progression-free survival (PFS) in chronic lymphocytic leukemia (CLL) patients. Lenalidomide (LEN) has antiproliferative and immunomodulatory effects in CLL and may improve response following CIT (Buhler et al 2016; Fink et al 2017). Here we report the final analysis of the phase III, randomized, CLL6 RESIDUUM trial, that aimed to determine whether LEN improves immunophenotypic (IP) complete response (CR) rates and extends remission duration in patients with CLL who have MRD following induction CIT. Methods The CLL6 trial was a joint trial of the ALLG and the FILO. CLL patients with CIRS score &amp;lt;6 requiring treatment according to iwCLL received 4 to 6 cycles of fludarabine, cyclophosphamide and rituximab (FCR). After completion of treatment, patients with clinical, radiological and/or flow cytometry evidence of MRD in blood (PB) or bone marrow (BM) were randomized 1:1 to receive 2 years of 10 mg daily LEN consolidation or observation (OBS). High sensitivity (HS) MRD were scheduled at month 3, 6 and every 6 months until month 24 then every 12 months until month 72 in PB and at screening and on months 12 and 24 in BM. The primary endpoint was time to clinical disease progression, or death, from randomization. The study planned to randomize 192 patients to detect a hazard ratio of 1.94, i.e., an increase in the % of patients remaining progression free at 4 years to 70% in the LEN arm compared with 50% in the OBS arm (two-sided log rank test at alpha = 0.05, no competing risks or loss to follow up, power = 0.86). Results The study closed prematurely because of an acute lymphoblastic leukemia (ALL) warning (3 of 56 patients [5.4%]) in the CLLM1 trial (Fink et al., 2017; Fürstenau et al., 2021). Between May 2011 and January 2018, 143 patients were randomized (70 in Australia and 73 in France) to the LEN (n=71) or OBS (n=72) arms. Median age was 63 [range 41-78], and 60 [26-79] years in the LEN and OBS arms respectively, 113 patients were males. At randomization, 27 (38 %) and 23 (32%) patients were in CR, 9 (13%) and 10 (14%) in nPR, 35 (49%) and 39 (54%) in PR in LEN and OBS arms respectively. Forty-nine (69%) and 47 (65%) had PB and 56 (79%) and 58 (81%) had BM detectable MRD in LEN and OBS arm respectively. Median follow-up (FU) is 52.6 months (range 44.9-59.0; LEN 49.8 [41.9-57.1], OBS 55.59 [44.0-61.7]). Twenty-eight (39%) patients progressed in the LEN arm versus 40 (56%) in the OBS arm (χ² p=0.01), 8 died in each arm. Median PFS was 64.6 (95%CI 47.7-not reached [NR]) months in the LEN arm versus 42.4 (32.3-61.6) months in the OBS arm (p=0.039). Multivariate analysis did not identify any predictive factor of relapse. Median overall survival was not reached (NR) (77.58-NR) in the LEN arm and 107.7 (107.6-NR) months in the OBS arm. There were 118 adverse events (AE), 87 in the LEN and 31 in the OBS arms respectively, with more neutropenia (n=21 vs n=1), gastrointestinal (n=10 vs n=4), respiratory (n=9 vs n=0) nervous system (n=6 vs n=1) and musculoskeletal (n=4 vs n=1) in the LEN arm. Most of the excess of AEs in LEN arm occurred after the end of the treatment. Severe AEs were reported in 35 patients (24.5%), 24 in the LEN arm and 11 in OBS. Fifteen secondary malignancies occurred: 8 in the LEN arm; 7 in the OBS arm. Six were of hematological origin (2 Richter transformation in each arm, 1 marginal zone lymphoma in the OBS arm and 1 myelodysplastic syndrome in the LEN arm). No case of ALL occurred. HS MRD analyses were performed in 71/73 patients in the French cohort. A follow-up was available in 65/71 with a median number of 7 time-points per patients (range 3-10). Different MRD kinetics were observed. While MRD rates in OBS arm increased in 33/34 patients, LEN consolidation led to long-lasting and transient deep IP CR in 4/31 and 9/31 patients respectively, MRD rate stabilization in 10/31 patients, and MRD increase in the remaining 6/31 patients. Conclusion The CLL6 RESIDUUM study demonstrated a significant benefit of consolidation therapy with lenalidomide in CLL patients with residual disease after FCR treatment. LEN resulted in a significantly longer PFS, with no unacceptable toxicity including ALL. Although FCR is no longer considered gold standard initial CLL therapy, eradicating residual disease can remain challenging with newer targeted agents. Patients with CLL MRD following initial therapy may experience prolongation in progression free survival from LEN consolidation.

Total Marrow and Lymphoid Irradiation (TMLI) -Based Conditioning Regimen in Patients with Acute Leukemia Undergoing Allogeneic Hematopoietic Cell Transplant with Measurable Residual Disease

Relapse of primary hematologic malignancy remains the leading cause of treatment failure afterallogeneic Hematopoietic cell transplantation (allo-HCT). Multiple studies have shown that presence of measurable residual disease (MRD), at the time of HCT, irrespective of the detection method, is associated with lower overall survival (OS) and relapse-free survival (RFS). In a recent meta-analysis of 11,151 patients with AML, Short et al., reported 5-year disease-free survival (DFS) of 25% for patients who have detectable MRD pre -HCT, compared to 64% for those without MRD. The 5-year OS was 34% and 68% for patients with or without MRD at HCT (JAMA Oncology 2020). In AML patients with genomic evidence of MRD before allo-HCT, myeloablative conditioning (MAC) regimens result in improved survival when compared to reduced intensity conditioning (RIC); (Hourigan et al, JCO 2020). Our center has pioneered and developed Total marrow and lymphoid irradiation (TMLI) that allows for delivery of higher dose of radiation to the sites with high disease burden (bone marrow and lymphoid organs), while sparing healthy tissues. In an ongoing Phase 2 trial (NCT02094794), we delivered TMLI (20Gy) with high dose chemotherapy to patients with high-risk leukemias (ALL or AML) undergoing allo-HCT from an HLA matched or mismatched donor. Here, we report on the results of our prospective analysis on a subset of patients of NCT02094794 who underwent allo-HCT with morphologic remission but had detectable MRD status in their pre HCT bone marrow biopsy (n=30). Conditioning regimen comprised of TMLI on days -9 to -5 (total of 20Gy), etoposide (60 mg/kg) on day -4, and cyclophosphamide (100mg/kg) on day -2. Unmanipulated peripheral blood stem cells (PBSC) graft from 10/10 HLA matched related or unrelated donor was infused on day 0 and graft-versus-host disease (GVHD) prophylaxis was tacrolimus and sirolimus-based. TMLI was delivered by intensity modulated radiation therapy (IMRT). MRD assay was done by either University of Washington flow cytometry with 0.01% - 0.1 % sensitivity, FISH/conventional cytogenetics, or NGS-based assays. Patient and HCT characteristics are summarized in Table 1. Briefly, the median age at the time of HCT was 36 years (range: 16-59) with the majority of patients receiving PBSC grafts (87%). Donors were match related (67%) or match unrelated (33%). The underlying diagnosis was AML (n=22; 73%), ALL (n=7; 23%), or CML-BC (n=1; 3%). Karnofsky performance status was 80-100 in 90% of patients and HCT-CI ≥3 was seen in 35% of patients. Pre-HCT MRD + status was documented by Flow cytometry MRD assay in 17 patients [AML (n=14) and ALL (n=3)], with mean MRD positivity of 2.9 % (range: 0.02-5.6%) for AML and 0.4% (range: 0.003-1.7%) for ALL patients. Thirteen additional patients had MRD positive status confirmed by FISH/cytogenetics (n=6 patients) or NGS (n=7). With a median duration follow up of 22.3 months (range: 6.0-81.1), the 1 and 2-year OS were 68% (95% CI: 0.47-0.82) and 59% (95% CI: 0.38-0.75), respectively. The 1 and 2- year disease-free survival (DFS) were 55% (95% CI: 0.34-0.71) and 45% (95% CI: 0.26-0.63), while the cumulative incidence (CI) of relapse at 1 and 2 years were 28% (95% CI: 0.13-0.46) and 33% (95% CI: 0.16-0.51), respectively. At day 100 post-HCT, the CI of NRM was 7%, grade 2-4 acute GVHD was 40% and Grade 3-4 acute GVHD was 13%. The CI of NIH moderate- severe chronic GVHD at 1- year was 35% (95% CI: 0.17-0.52). No difference in outcomes were noted in patients who were MRD positive by UWFC vs FISH/NGS testing. In conclusion, TMLI based conditioning regimen in patients undergoing allo-HCT with MRD+ disease from matched donors is associated with improvement in 2-year RFS/OS and is associated with low NRM compared to historic controls. The current phase 2 study is enrolling patients at our center.

Ultrasensitive chimerism enhances measurable residual disease testing after allogeneic hematopoietic cell transplantation

AbstractIncreasing mixed chimerism (reemerging recipient cells) after allogeneic hematopoietic cell transplant (allo-HCT) can indicate relapse, the leading factor determining mortality in blood malignancies. Most clinical chimerism tests have limited sensitivity and are primarily designed to monitor engraftment. We developed a panel of quantitative polymerase chain reaction assays using TaqMan chemistry capable of quantifying chimerism in the order of 1 in a million. At such analytic sensitivity, we hypothesized that it could inform on relapse risk. As a proof-of-concept, we applied our panel to a retrospective cohort of patients with acute leukemia who underwent allo-HCT with known outcomes. Recipient cells in bone marrow aspirates (BMAs) remained detectable in 97.8% of tested samples. Absolute recipient chimerism proportions and rates at which these proportions increased in BMAs in the first 540 days after allo-HCT were associated with relapse. Detectable measurable residual disease (MRD) via flow cytometry in BMAs after allo-HCT showed limited correlation with relapse. This correlation noticeably strengthened when combined with increased recipient chimerism in BMAs, demonstrating the ability of our ultrasensitive chimerism assay to augment MRD data. Our technology reveals an underappreciated usefulness of clinical chimerism. Used side by side with MRD assays, it promises to improve identification of patients with the highest risk of disease reoccurrence for a chance of early intervention.

Outcomes following brexucabtagene autoleucel administered as an FDA-approved therapy for adults with relapsed/refractory B-ALL.

7001 Background: In October 2021, brexucabtagene autoleucel (brexu-cel) became the first CAR-T cell therapy to receive FDA approval for adults (≥18 yrs) with relapsed/refractory (r/r) B-ALL. Approval was based on Phase II results of ZUMA-3, a single-arm, open-label, multicenter trial which reported on 55 treated patients with CR/CRi achieved in 71%; cytokine release syndrome (CRS) and neurologic toxicities occurred in 89% (grade 3-4, 24%) and 60% (grade 3-4, 25%), respectively. Here, we report outcomes of 76 adults with r/r B-ALL treated with post-approval brexu-cel at 13 U.S. centers. Methods: Retrospective data were collected across centers participating in a real-world outcomes collaborative of CAR-T in ALL (ROCCA). Descriptive statistics, Kaplan-Meier methodologies and cumulative incidence functions were used to summarize outcomes. Results: Among 76 patients infused, median age was 44 yrs (range, 18-81); 54% were male, 57% were non-Hispanic White (25% Hispanic), and 71% had Ph-neg disease. Median number of previous lines of therapy was 3.5 (range, 1-9) including blinatumomab in 53% and inotuzumab in 37%; 46% had relapsed post-transplant. Prior to apheresis, 69% of patients had active disease ( &gt; 5% marrow blasts or presence of extramedullary disease), including 8 patients with CNS3 disease, 19% had detectable measurable residual disease (MRD) only, and 12% were MRD-neg. Median time from apheresis to infusion was 31 days. Lymphodepletion was predominantly with flu/cy (88%); 5 received cy/cladribine, and one patient each received single agent cy, single agent cladribine, and single agent bendamustine. Among 65 patients at least 28 days post-CAR-T with response assessed, 90.8% achieved CR/CRi, of whom 83% were MRD-neg, including CNS disease clearance in 7/8 CNS3 patients. CRS and ICANS (ASTCT criteria) occurred in 81.6% (grade 3-4, 6.6%) and 59% (grade 3-4, 38.6%), respectively. Median follow-up for survivors was 196.5 days (IQR 135.5-284.5). At last follow-up, 21 patients progressed/relapsed and 13 had died (7 of B-ALL; 6 of neurotoxicity/infection). Cumulative incidence of relapse and death in remission at 180 days were 31.5% (95% CI: 19.7%-44.1%) and 8.9% (95% CI: 3.5%-17.5%), respectively, while six-month PFS and OS were 58.8% (95% CI: 44.6%-70.5%) and 86.7% (95% CI: 75.8%-92.9%), respectively. Eleven patients underwent allogeneic transplant in CR/CRi after brexu-cel; all of whom remain in remission at last follow-up. Conclusions: These data are the first to demonstrate post-approval efficacy and toxicity rates of brexu-cel in adults with r/r B-ALL. Unlike the ZUMA-3 population, 31% of patients infused in this real-world cohort lacked morphologically detectable disease and 8 had CNS3 prior to apheresis. Our data confirm high response rates associated with brexu-cel in adult ALL, but also highlight the need for interventions to reduce associated toxicities.