scholarly journals Conventional and Flowcytometric Minimal Residual Disease Based Risk Stratified Post Remission Therapy Improves Survival in Ph-Negative Pediatric Acute Lymphoblastic Leukemia- Single Centre Experience from South India

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4119-4119
Author(s):  
Rema Ganapathy ◽  
Aswathy Ashok Beenakumari ◽  
Syamaprasad Vinayakumar ◽  
Remya Sudevan ◽  
Renjitha Bhaskaran ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
Risk Stratification ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Treatment Algorithm ◽  
Middle Income ◽  
Middle Income Countries ◽  
Minimal Residual

Abstract Background: Children with Acute Lymphoblastic Leukemia (ALL) in Low Middle income countries(LMIC) face major challenges including treatment abandonment and poor overall survival (OS) and event-free survival (EFS).The preliminary data and results of outcome of Pediatric ALL from our pediatric hematology-oncology center which follows BFM based ALLtreatment protocol has been published in 2015 in ASH forum.Due to non availability of Polymerase chain reaction (PCR)based Minimal residual disease(MRD)analysis, we use multiparametric flowcytometry (FCM) based MRD analysis for remission assessment and risk stratification in our patients. Within resource constraints, we present evidence that outcomes comparable with that seen in high income (HIC)and upper middle income countries(UMIC) can be achieved with a post remission therapy guided by a risk stratification incorporating FCM MRD. Methods: Following IRB approval,an ambidirectional cohort study was performed using clinical information and outcomes of all patients aged 1to 14 years treated for newly diagnosed B- or T-ALL between January 1,2015 and December 31, 2020. AIEOP BFM ALL 2009 protocol with modifications was followed as the institutional protocol in all patients.The treatment algorithm is mentioned in Figure 1. Patients who underwent multiparametric FCM MRD analysis at the end of Induction IA and whose 6 months follow up details were available were included in the analysis. Patients with Ph positive ALL and those who died during Induction IA were excluded. FCM MRD analysis was performed after Induction IA on Day 33.MRD level above 0.01% was considered positive.MRD assessment was repeated following Induction IB on Day 74 in patients who had MRD positivity on Day 33. At the end of Induction IB patients were risk stratified into High risk(HR) and non High risk(Non HR).HR features included Hypodiploidy(<45chromosomes), Positivity for MLL/AF4 or t(4:11),poor prednisolone response(absolute blast count in peripheral blood ≥1 x 10^9/l on Day 8 of initiation of prednisolone) and non remission on Day33. Patients who had persistent MRD positive on Day74 were reallocated to high risk. Treatment with HR protocol was initiated for high risk patients whenever financially manageable.Statistical analysis was done using SPSS version 21 OS and EFS were assessed by Kaplan-Meier method Patients were censored at last follow-up. Results: Median follow-up time was 33.5(4-102) months . Study had 102(n=102) consecutive Ph negative patients who underwent induction therapy. Six patients (5.88%) died during induction IA;96(n=96) children who continued treatment were included in further analysis. The mean age at diagnosis was 6(1-14) years .Forty seven (48.95%)patients were male..B-ALL n=84(87.5%) and T ALL n=12.(12.5%). Four patients(4.16%) had CNS disease at diagnosis. Three children (3.13%) had high risk cytogenetics.Ten children (10.42%)in the cohort had poor prednisolone response. Five patients(5.20%) didnot achieve morphological remission on Day33. Fifteen (15.63%) patients were risk stratified as HR during IA. Four more (4.16%) were reallocated to HR in view of persistent MRD positivity after Induction IB. At median follow-up, the OS was 95.35%±2.65(95% CI 90.16-100.54) and the EFS 94.48%±2.74 (95% CI, 89.11%-99.84%).Female gender predicted better EFS (p=0.042).The EFS of patients without CNS disease at presentation was significantly better(93.5% Vs 23.2% p=0.000). The EFS at median follow up of patients in re HR cohort was 64.19% Vs 97.81% in non HR (p=0.010). EFS by risk stratification is shown in Figure II. Conclusion:Our study suggests that FCM MRD can be successfully incorporated into the treatment algorithm in a resource limited setting. With FCM MRD were able to identify an additional subset of HR patients who otherwise would have been stratified into non HR group. In a prospective cohort , FCM MRD could be tested at an earlier time point in IA induction to facilitate identification of early drug responsive patients with lowest risk of relapse. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Integrated Use of Minimal Residual Disease Classification and IKZF1 Alteration Status Accurately Predicts 79% of Relapses In Pediatric Acute Lymphoblastic Leukemia

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 272-272 ◽  
Author(s):  
Esmé Waanders ◽  
Vincent H.J. van der elden ◽  
Ellen van der Schoot ◽  
Frank N. van Leeuwen ◽  
Simon V. van Reijmersdal ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
Risk Stratification ◽  
Minimal Residual Disease ◽  
Residual Disease ◽  
Risk Group ◽  
Lymphoblastic Leukemia ◽  
Wild Type ◽  
Pediatric Acute Lymphoblastic Leukemia ◽  
Minimal Residual

Abstract Abstract 272 The response to therapy as determined by minimal residual disease (MRD) is currently used for stratification in treatment protocols for pediatric acute lymphoblastic leukemia (ALL). Even though MRD classification clearly identifies patients at low or at high risk for relapse, it also results in a large intermediate group (50 to 60% of patients), which still contains approximately half of all relapse cases. To improve risk stratification, we evaluated the added value of the IKZF1 alteration status, recently identified as a prognostic factor, in precursor-B-ALL patients. In an unbiased cohort of 131 uniformly treated precursor-B-ALL patients, we determined MRD levels at 42 and 84 days after treatment initiation using RQ-PCR analysis of Ig/TCR rearrangements. Based on these levels, patients were divided into three groups: MRD-Low (MRD-L), MRD-Medium (MRD-M) and MRD-High (MRD-H). IKZF1 alterations at diagnosis were determined using multiplex ligation-dependent probe amplification and genomic sequencing. We confirmed the strong prognostic significance of MRD classification, which was independent of IKZF1 status. Importantly, in the large MRD-M group (n=81; 62% of patients) containing 46% of the relapsed patients, IKZF1 alteration status identified 8 out of 11 relapsed patients (72%). The 9 year relapse-free survival (RFS) for IKZF1 mutated patients in this MRD-M group was 27% compared to 96% for patients wild-type for IKZF1 (P<0.001). Based on these results, we defined a new parameter integrating both MRD and IKZF1 status. The favorable risk group included patients classified as MRD-L or MRD-M with IKZF1 wild-type (n=104; 5 relapses), whereas the high risk group consisted of MRD-H patients or MRD-M patients with IKZF1 alterations (n=27; 19 relapses). This parameter showed stronger prognostic value than each of the established risk factors alone (Hazard Ratio[95%CI]: 24.98[8.29-75.31]). Importantly, whereas MRD and IKZF1 status alone identified only 46% and 54% of relapses, respectively, their integrated use allowed prediction of 79% of all relapses with 93% specificity. In conclusion: The use of a new parameter integrating MRD and IKZF1 status results in an unprecedented sensitivity in upfront relapse prediction and has a high potential for future risk stratification, particularly for patients originally classified as non-high-risk, such as the large group of MRD-M patients. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Clinical Features and Survival According to Minimal Residual Disease in a Colombian Population Diagnosed with B-Cell Acute Lymphoblastic Leukemia

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4459-4459
Author(s):  
Angela María Peña ◽  
Sandra Vanesa Rios ◽  
Luis Antonio Salazar ◽  
Manuel Rosales ◽  
Sara Ines Jimenez ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
B Cell ◽  
Research Funding ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Advisory Board ◽  
The Other ◽  
Minimal Residual

Abstract Introduction Acute lymphoblastic leukemia (ALL) is a clonal hematopoietic disorder that originates from B or T lymphoid progenitors and has well validated prognostic and predictive factors that influence outcomes. One of the strongest prognostic factors is the detection of minimal residual disease (MRD) which measures residual cell population after treatment when a morphologic complete response has been achieved. MRD positivity is associated with a higher risk of relapse and poor response to chemo or radiotherapy Objectives The aim of the study was to assess the prognostic impact of post-induction MRD status in a cohort of ALL Colombian patients in terms of relapse-free survival (RFS) and overall survival (OS). Methods This is a retrospective observational study conducted at a Colombian university hospital and included a cohort of ALL patients diagnosed between 2013 and 2020 treatment according to protocol PETHEMA (Spanish Program for Hematology Treatments). MRD was measured with 8-color flow cytometry evaluate on bone marrow. MRD status was classified as negative MRD (NMRD) or positive MRD (PMRD) based on a sensitivity threshold of &lt;0,01% or ≥0,01% leukemic cells, respectively, following to international guides. Demographic and clinical characteristics were analyzed using descriptive statistics. Kaplan-Meier method was used to assess overall RFS and OS. Results A total 128 patients were included. The median age at diagnosis was 34 years (range 0-89 years), 54% were men, 26% were overweight, 22% obese, 6.2% had type 2 DM (T2DM), and most had a ECOG PS of £2 (94%). Most patients (80.5%) had high risk according PETHEMA, B-ALL and were classified as ALL-2 (58%) according to FAB classification with Pre-B cell ALL being the most common phenotype (54.7%). Ph+ ALL was diagnosed in 12% of patients. Most used treatments protocols were PETHEMA-AR and PETHEMA-RI in 43.8% and 11.6% of patients, respectively. Post-induction MRD measurement was available in 98 patients, 36 (36.7%) had NMRD and 62 (63.3%) PMRD. From the 36 patients with NMRD, eight patients (22.2%) received Allogeneic Hematopoietic Stem Cell Transplantation (alloHSCT): two of them, were transplanted in first complete remission, one because of high risk and the other one for BCR-ABL positivity. The other six patients received alloHSCT in second remission and all of them relapsed after late consolidations. Finally, alloHSCT was done in 28 patients with PMRD (45.2%). The 12-month OS for patients with NMRD was 68.7% (95%CI 50.5-81.2) compared to 63.7% (95%CI 50.3-74.4) in the ones with PMRD, p=0.375. 12-month RFS was 83.3% (95%CI 61.5-93.4) in patients with NMRD and 90.0% (95%CI 72.1-96.7) in patients with PMRD, p=0.436. (Figure 1). OS was significantly higher for the PMRD patients who underwent AlloHSCT 96.4% (95%CI 77.2-99.4) versus not underwent 36.8% (95%CI 20.6-53.2), HR: 0.39 (95%CI 0.005-0.29) p=0.002 (Figure 2). Conclusion MRD assessment is a strong prognostic in ALL, however it was not associated with significant differences in RFS or OS in this single institution cohort of Colombian patients. Patients with PMRD taken to AlloHSCT had superior OS compared to NMRD that underwent transplant. A small sample size and short follow-up could explain our results. Larger cohorts with extended follow up and with different MRD methods are needed to better understand the role of MRD assessment in minority ALL populations, such as Colombian patients. Figure 1 Figure 1. Disclosures Peña: Amgen: Research Funding. Salazar: Amgen: Research Funding. Sandoval-Sus: BMS: Other: Advisory Board, Speakers Bureau; SeaGen, Janssen, MassiveBio, TG: Other: Advisory Board. Sossa: Amgen: Research Funding.

scholarly journals Personalized therapy in pediatric high-risk B-cell acute lymphoblastic leukemia

2020 ◽  
Vol 11 ◽  
pp. 204062072092757 ◽  
Author(s):  
Seth E. Karol ◽  
Ching-Hon Pui
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Pediatric Acute Lymphoblastic Leukemia ◽  
Risk Patients ◽  
Cell Acute Lymphoblastic Leukemia ◽  
Disease Stratification ◽  
Cure Rates ◽  
Minimal Residual

Although cure rates for pediatric acute lymphoblastic leukemia (ALL) have now risen to more than 90%, subsets of patients with high-risk features continue to experience high rates of treatment failure and relapse. Recent work in minimal residual disease stratification and leukemia genomics have increased the ability to identify and classify these high-risk patients. In this review, we discuss this work to identify and classify patients with high-risk ALL. Novel therapeutics, which may have the potential to improve outcomes for these patients, are also discussed.

Status of Minimal Residual Disease Determines Outcome of Autologous HSCT in Adults with High-Risk Acute Lymphoblastic Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2321-2321
Author(s):  
Sebastian Giebel ◽  
Beata Stella-Holowiecka ◽  
Malgorzata Krawczyk-Kulis ◽  
Nicola Goekbuget ◽  
Dieter Hoelzer ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
Minimal Residual Disease ◽  
Peripheral Blood ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Minimal Residual

Abstract Abstract 2321 Poster Board II-298 The role of autologous hematopoietic stem cell transplantation (autoHSCT) in the treatment of adult acute lymphoblastic leukemia (ALL) is a subject of controversies as several prospective studies failed to prove its advantage over maintenance chemotherapy. Those studies, however, did not take into account the status of minimal residual disease (MRD), which is now recognized a potent predictor for relapse among patients treated with conventional-dose chemotherapy. The goal of this analysis was to determine the impact of MRD on outcome of autoHSCT. Data on 123 autoHSCT recipients collected from 6 study groups cooperating in the European Leukemia Net were analyzed. Median age of 77 B-lineage and 46 T-lineage high-risk ALL patients was 31 (16-59) years. Ph+ ALL was recognized in 20 cases. All patients were in first complete remission (CR) lasting 6 (1.5-22) months. Peripheral blood was used as a source of stem cells in 67 patients whereas bone marrow, in 56 cases. Conditioning was based on chemotherapy alone (n=76) or total body irradiation (n=47). MRD was evaluated in bone marrow with the use of either multiparametric flow cytometry (n=79) or molecular techniques (n=44). MRD level of 0.1% bone marrow cells was used as a cut-off point for the purpose of this study. At the time of autoHSCT MRD was &0.1% in 93 patients and ≧0.1% in 30 cases. With the median follow up of 5 years, the probability of leukemia-free survival (LFS) at 5 years for the whole group equaled 48% (+/-5). Three patients died of transplantation-related complications. The LFS rate was significantly higher for patients with the MRD level at transplantation &0.1% compared to those with MRD ≧0.1% (57% vs. 19%, p=0.0002). The difference was particularly pronounced for peripheral blood HSCT (66% vs. 20%, p=0.0006) and for T-lineage ALL (62% vs. 8%, p=0.001). In a multivariate analysis adjusted for other potential prognostic factors (age, CR duration, Ph+ ALL, immunophenotype, source of stem cells, type of conditioning), the MRD status &0.1% remained the only independent factor associated with increased LFS (HR=2.5, p=0.0009). CONCLUSIONS: MRD status is the most important predictor for LFS after autoHSCT in adults with ALL. More than half of patients with high risk disease and low MRD level at the time of transplantation may be cured. This observation may contribute to re-evaluation of the role of autoHSCT in the therapy of adult ALL. Disclosures: No relevant conflicts of interest to declare.

Minimal Residual Disease At 3 Months, Combined to the Presence of IKZF1 Deletion in B-Lineage or Absence of NOTCH1 pathway Mutation in T-Lineage, Recapitulates the Disease Risk Assessment in Adults with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia - A GRAALL Study

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 572-572 ◽  
Author(s):  
Kheira Beldjord ◽  
Elizabeth Macintyre ◽  
Véronique Lhéritier ◽  
Marie-Laure Boulland ◽  
Thibaut Leguay ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
High Risk ◽  
Minimal Residual Disease ◽  
Disease Risk ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Philadelphia Chromosome ◽  
Cns Involvement ◽  
Risk Patients ◽  
Minimal Residual

Abstract Abstract 572 Aim. In recent series of adults with acute lymphoblastic leukemia (ALL), the GRAALL (ASH 2009, abstract 577) and other cooperative groups have confirmed the strong prognostic value of Ig/TCR minimal residual disease (MRD) on patient outcome. Despite this, age, WBC, CNS involvement, recurrent chromosomal translocations, and early response to steroids and chemotherapy remain frequently used to tailor post-remission therapy and envision allogeneic stem cell transplantation (SCT) in most adult ALL trials. We updated our MRD study, now with 262 patients who all achieved complete remission (CR) after the first induction and were assessed for MRD after induction (MRD1, at 6 weeks) and consolidation (MRD2, at 12 weeks). One hundred and fifty-eight patients had Philadelphia chromosome (Ph)-negative B-cell precursor ALL (BCP-ALL), while 104 had T-cell ALL (T-ALL). Since 107 of the BCP-ALL (68%) were studied for IKZF1 deletion and 90 of the T-ALL patients (87%) for NOTCH1/FBXW7 mutations, we were able to reassess the MRD significance according to these newly described oncogenic markers. These two covariates (i.e. MRD and IKZF1/NOTCH1/FBXW7 genetics) allowed us to redefine a much simpler yet more powerful stratification of disease risk in both BCP- ALL and T-ALL subsets. Methods. All 262 patients studied (median age, 31.5 years) were treated in the GRAALL-2003 and GRAALL-2005 trials. Although they were younger and had more frequently circulating blasts, other characteristics and outcome did not differ from patients treated in the same trials but not assessed for MRD. Ig/TCR MRD levels were determined according to Euro-MRD guidelines (Leukemia 2007;21:604). IKZF1 deletions were assessed by multiplex multi-fluorescent PCR. NOTCH1/FBXW7 mutations were assessed as previously described (Blood 2009;113:3918). Multivariate backward stepwise selection Cox models were used for the cumulative incidence of relapse (CIR), disease-free (DFS) and overall survival (OS) endpoints, after censoring transplanted patients at SCT. Models were always adjusted on age (35-year cutoff), WBC (30 and 100 G/L cutoff for BCP- and T-ALL, respectively), CNS involvement, and trial. Additional BCP-specific covariates included CD20 expression, t(4;11) and t(1;19) translocations, and IKZF1 deletion. Additional T-specific covariates included cortical immunophenotype according to the EGIL classification, TLX1 overexpression, and NOTCH1/FBXW7 mutation. Finally, allogeneic SCT was re-evaluated in the newly defined risk subsets, as a time-dependent covariate. Results. An initial multivariate analysis revealed that among blood response after 1 week of steroid, bone marrow response after 2 weeks of therapy, and molecular response at both MRD1 and MRD2 time-points, the MRD2 level was the main and sole independent predictor of relapse (P=0.003). In BCP-ALL patients, persistent MRD2 and IKZF1 deletion were the only two independent factors identified, the presence of at least one factor defining 51% high-risk patients with 52% versus 15% CIR (HR, 3.8; P= 0.008), 41% versus 81% DFS (HR, 3.6; P= 0.005), and 54% versus 80% OS (HR, 3.9; P= 0.015) at 4 years. Allogeneic SCT in first CR significantly decreased relapse incidence and prolonged DFS in these new high-risk BCP-ALL patients (HR, 0.23 and 0.40; P= 0.016 and 0.05, respectively). In T-ALL patients, persistent MRD2 and lack of NOTCH1/FBXW7 mutation were the only two independent factors identified, the presence of at least one factor defining 49% high-risk patients with 64% versus 12% CIR (HR, 6.4; P= 0.002), 36% versus 88% DFS (HR, 6.4; P= 0.002), and 41% versus 95% OS (HR, 7.3; P= 0.015) at 4 years. SCT had no significant effect on relapse incidence and DFS in these new high-risk T-ALL patients. Conclusion. In adult patients with Ph-negative ALL treated with the pediatric-inspired GRAALL regimen, IKZF1 deletion in BCP-ALL, NOTCH1/FBXW7 mutation in T-ALL, and MRD at 3 months in both subsets replace all classical risk factors, leading to a new simplified prognostic scoring system based only on IKZF1 and NOTCH1/FBXW7 genetics and MRD clearance. This new risk score identifies approximately half of the patients as good-risk, with a relapse incidence as low as 10–15%. It will be validated and used prospectively in the next generation of GRAALL trials, to stratify both new drug evaluation and SCT in first CR. Disclosures: No relevant conflicts of interest to declare.

Droplet Digital PCR Analysis for Diagnosis and Minimal Residual Disease Monitoring in Adult Ph+ Acute Lymphoblastic Leukemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4989-4989 ◽  
Author(s):  
Nicoletta Coccaro ◽  
Antonella Zagaria ◽  
Luisa Anelli ◽  
Giuseppina Tota ◽  
Paola Orsini ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Residual Disease ◽  
Lymphoblastic Leukemia ◽  
Fusion Transcript ◽  
Digital Pcr ◽  
Droplet Digital Pcr ◽  
Pcr Analysis ◽  
Rt Pcr ◽  
Minimal Residual

Abstract Introduction. BCR-ABL1 tyrosine kinase inhibitors (TKIs) are considered an important component of treatment for adult patients affected by Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). In fact, recent studies reported that treating Ph+ ALL with the combination of imatinib and multi-agent chemotherapy improved the overall outcome. Currently, no data are available on the impact of TKIs on minimal residual disease (MRD) in Ph+ ALL. In fact, although the real-time quantitative PCR (RQ-PCR) method, usually employed for monitoring the BCR-ABL1 residual transcript, is sensitive and easy to perform, it lacks a full standardization and international quality validation. Here, we describe a highly sensitive and reproducible droplet digital PCR (ddPCR) test to monitor BCR-ABL1 transcript level in Ph+ ALL. Methods. BCR-ABL1 expression analysis by ddPCR was performed in twenty-two newly diagnosed adult Ph+ ALL patients.The diagnosis was confirmed by qualitative RT-PCR specific for the BCR-ABL1 p190 fusion gene detection. ddPCR experiments were successfully performed in all twenty-two patients at the onset; several follow-up points were evaluated in thirteen patients. ddPCR experiments were performed using primers and probes specific for BCR-ABL1 p190. GUSB was used as control gene. Fifty ng and 750 ng of cDNA templates were used for the onset and for the post-treatment samples, respectively. To increase the limit of detection (LOD), three replicates were run for the post-treatment samples. ddPCR experiments were performed by Bio-Rad's QX200 system and ddPCR data were analyzed with QuantaSoft analysis software (version 1.7.4). Target concentration was expressed as BCR-ABL1 copies/mg. Results. First, we defined the LOD of the BCR-ABL1 p190 ddPCR system, a 10-fold dilution series (100, 10-1, 10-2, 10-3, 10-4, and 10-5) of a pool of p190 positive patients using a diluent-pool of healthy volunteers. This analysis showed remarkable linearity, trueness, and precision down to 10-5. After converting to log-log scale, linear regression showed no concentration-dependent bias, and R2 equaled 0.996. Because the negative samples showed no background, even the detection of a single droplet per well was considered a positive result. The median concentration of the BCR-ABL1 transcript at the onset was 233.8 (min 3.24 - max 1744) x 103BCR-ABL1 copies/mg. Concerning the analysis of follow-up samples, among the thirty-four points that were negative to qualitative nested RT-PCR, twenty-three (68%) resulted to be positive by ddPCR analysis, with a median concentration of 44.95 (min 0.27 - max 573.3) BCR-ABL1 copies/mg. Follow-up points that were negative in ddPCR remained negative even when the experiments were repeated increasing the depth of the analysis, evaluating a total quantity of 4.5 mg of RNA. Conclusions. This study indicates that, as compared to RQ-PCR, ddPCR increases the depth of the quantitative analysis of BCR-ABL1 p190 fusion transcript by allowing the evaluation of larger amounts of RNA. Moreover, our preliminary data revealed that the amount of the BCR-ABL1 fusion transcript at diagnosis is heterogeneous and that the ddPCR is much more sensitive than nested qualitative RT-PCR analysis, as the 68% of samples negative to nested PCR during the follow-up resulted to be positive by ddPCR. Therefore, we suggest that ddPCR represents a precise, sensitive and rapid method for both diagnosis and MRD monitoring of Ph+ ALL patients. Disclosures No relevant conflicts of interest to declare.

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