Interphase FISH on TEL/AML1 positive acute lymphoblastic leukemia relapses – analysis of clinical relevance of additional TEL and AML1 copy number changes

Objectives: TEL/AML1 (ETV6/RUNX1) fusion resulting from the translocation t(12;21)(p13;q22) constitutes the most common chimeric fusion gene in initial childhood B‐cell precursor (BCP) acute lymphoblastic leukemia (ALL) (19–27%) and has been associated with good prognosis. Three secondary aberrations in TEL/AML1 positive ALL have been suspected to negatively influence outcome: deletion of the second TEL allele (T), gain of the second AML1 allele (A) and duplication of the derivative chromosome 21 (der(21), TA). Many studies have explored such aberrations in initial disease, while only few reports have investigated them in relapses. Methods: In this study, bone marrow samples from 38 children with relapsed TEL/AML1 RT‐PCR positive and negative BCP‐ALL were analyzed for these mutations by interphase fluorescence in situ hybridization and results were compared with published data. Results: In children with TEL/AML1 positive ALL relapse, additional (a) TEL loss, (b) combined AML1 and der(21) gain, (c) combined TEL loss and AML1 gain as well as (d) the occurrence of a subpopulation with the signal pattern 1T/3A/1TA appear to be related to higher peripheral blast counts (PBCs) at relapse diagnosis (a and d) or a tendency towards the occurrence of a subsequent relapse (b and c) (P‐values <0.05). Conclusions: Our data together with published results on TEL/AML1 positive ALL suggest that frequencies of additional TEL and AML1 mutations are, with the exception of loss of untranslocated TEL, higher in first relapses than in initial disease. They also show that it is important to consider combined mutations in the analysis of this leukemia entity.     

Minimal residual disease studies are beneficial in the follow-up of TEL/AML1 patients with B-precursor acute lymphoblastic leukaemia

The t(12;21)(p13;q22) translocation has been identified as the most common chromosomal abnormality in childhood acute lymphoblastic leukaemia (ALL). Initially, several investigators reported an excellent prognosis in paediatric leukaemias with this translocation, but other studies showed a 20% incidence in relapsed ALL. We performed an extensive analysis of 90 ALL patients. In 17 (19%) cases a TEL/AML1 fusion was found. However, this group was not representative as it included a high number of relapsed patients compared with the normal incidence in B-precursor ALL [54 in continuous complete remission (CCR) and 36 relapsed patients] and only a slightly better prognosis for TEL/AML1-positive patients was found (not significant) (four relapses in 17 TEL/AML1-positive patients vs. 32 relapses in 73 TEL/AML1-negative patients). Comparison of known prognostic factors (age, sex, ploidy, white blood cell count and immunophenotype) between relapsed TEL/AML1-positive and TEL/AML1-positive patients in CCR did not reveal differences, except that the white blood cell count was significantly higher in the relapsed group (P = 0.001). Time between diagnosis and relapse was not different for the relapsed TEL/AML1-positive group vs. the relapsed TEL/AML1-negative group. In 11 TEL/AML1-positive patients, the minimal residual disease (MRD) level at the end of induction therapy was quantified in a limiting dilution assay using IGH or TCRD junctional regions as polymerase chain reaction (PCR) targets. In all four relapsed patients, the level of MRD at the end of induction therapy was high (range 0.24-1.2%), whereas in all seven CCR patients, the MRD level was extremely low (0.02 to < 0.001%). In agreement with previous studies in which MRD levels at the end of induction therapy were found to be the strongest risk factor independent of other risk factors, in the present study we show that the MRD level remains a risk factor independent of the presence of a TEL/AML1 fusion gene.     

Relatively favorable outcome after allogeneic stem cell transplantation for BCR‐ABL1‐positive AML: A survey from the acute leukemia working party of the European Society for blood and marrow transplantation (EBMT)

The aim of the study was to assess the role of allogeneic stem cell transplantation (SCT) in patients diagnosed with BCR‐ABL1‐positive acute myeloid leukemia (AML). Fifty‐seven patients (median age, 48 years, range: 19‐67) with BCR‐ABL1 positive AML undergoing SCT were identified. The majority of the patients (70%) received a TKI before the transplant. At SCT 48 patients were in CR (45 in CR1), while 9 patients were transplanted in a more advanced stage of the disease. MRD was negative (BCR‐ABL1/ABL < 10⁴) at time of SCT in 36.1% (14/40). After SCT, 16 (61.5%) out of 26 patients with MRD positive at transplantation reached MRD negativity. After a median follow‐up of 6.3 years (0.7–14.2), NRM, RI, LFS, OS, and GRFS at 5 years were 18.1%, 37%, 44.2%, 53.8%, and 32.1%, respectively. The cumulative incidence of acute GvHD grade II‐IV was 16.4%, incidence of chronic GvHD 24.9%, and of extensive cGvHD 21.4%, respectively. In patients who received SCT in CR1, 5‐yr NRM, RI, LFS, OS, and GRFS were 15.9%, 36.4%, 46.5%, 59.4%, and 34.9%, respectively. Univariate analysis showed that age (<50 vs. ≥50 years) was associated with RI (5‐yr: 22.7 vs. 50%), LFS (5‐yr: 61.9 vs. 31.8%), and GRFS (5‐yr: 52.4 vs. 18.2%), whereas MRD‐negative status before SCT was associated with an improved GRFS (38.9 vs. 16.7%). We conclude that the outcome of patients <50 years of age with BCR‐ABL1‐positive AML receiving allogeneic SCT in CR is relatively favorable, possibly reflecting the beneficial effect of the use of TKI.     

Interphase fluorescence in situ hybridization and spectral karyotyping reveals hidden genetic aberrations in children with acute lymphoblastic leukaemia and a normal banded karyotype

Twenty-two cases of childhood acute lymphoblastic leukaemia (ALL) with normal G- or Q-banded karyotypes were studied by interphase fluorescence in situ hybridization (FISH) and spectral karyotyping. Probes detecting MLL, BCR/ABL and TEL/AML1 rearrangements were used for the interphase studies, along with centromere-specific probes from chromosomes 17 and X. In 10 patients (45%), previously undetected aberrations were demonstrable. Specific gene rearrangements and structural changes were found in six cases and numerical changes in five. Five of these aberrations have previously been reported to have an impact on prognosis. Three cases were massively hyperdiploid and, in one, the prognostically important BCR/ABL fusion was detected. In addition, a near-haploid karyotype with 27 chromosomes was found in one patient and TEL/AML1 rearrangements were detected in two cases. This study indicates that about half of childhood ALL cases with apparently normal karyotypes harbour genetic aberrations that may be detected using interphase FISH and spectral karyotyping.     

Multiple clonal MLL fusions in a patient receiving CHOP-based chemotherapy

MLL rearrangements were analysed in the blood of a patient receiving chemotherapy for diffuse large B‐cell lymphoma using inverse polymerase chain reaction targeting exon 12, parallel sequencing and a custom algorithm design. Of thirteen MLL rearrangements detected, five were capable of generating MLL fusion genes, including MLL‐MLLT3, the most common fusion in acute myeloid leukaemia (AML). Other fusions, all previously clinically unobserved, included MLL‐NKD1, a fusion to the negative regulator of Wnt/β‐catenin signaling, a pathway linked to leukaemic cell proliferation. The majority of the fusions exhibited clonal persistence from before treatment until 6 months post‐chemotherapy, suggesting the fusions may confer a survival advantage to the mutant clone. MLL breakpoints were partly clustered at a specific location, indicating commonality in the process of their formation. Further, the same MLL breakpoint location exhibited a 50–100‐fold increase in C to T transitions, consistent with attack by activation‐induced cytidine deaminase (AICDA). As is also observed in AML and acute lymphoblastic leukaemia, in this single patient setting, MLL is capable of interacting with multiple fusion partners. This finding defines a discrete site of MLL susceptibility to fragmentation, linked to possible deregulation of AICDA function.     

The distribution of MLL breakpoints correlates with outcome in infant acute leukaemia

Acute leukaemia in early childhood ‐ and mainly infant leukaemia (IL) – is characterized by acquired genetic alterations, most commonly by the presence of distinct MLL rearrangements (MLL‐r). The aim of this study was to investigate possible correlations between clinical features and molecular analyses of a series of 545 childhood leukaemia (≤24 months of age) cases: 385 acute lymphoblastic leukaemia (ALL) and 160 acute myeloid leukaemia (AML). The location of the genomic breakpoints was determined in a subset of 30 MLL‐r cases. The overall survival of the investigated cohort was 60·5%, as determined by the Kaplan‐Meier method. Worse outcomes were associated with age at diagnosis ≤6 months (P < 0·001), high white blood cell count (P = 0·001), and MLL‐r (P = 0·002) in ALL, while children with AML displayed a poorer outcome (P = 0·009) regardless of their age strata. Moreover, we present first evidence that MLL‐r patients with poor outcome preferentially displayed chromosomal breakpoints within MLL intron 11. Based on the literature, most MLL‐r IL display a breakpoint localization towards intron 11, which in turn may explain their worse clinical course. In summary, the MLL breakpoint localization is of clinical importance and should be considered as a novel outcome predictor for MLL‐r patients.     

Applicability of IG/TCR gene rearrangements as targets for minimal residual disease assessment in a population‐based cohort of Swedish childhood acute lymphoblastic leukaemia diagnosed 2002–2006

Minimal residual disease (MRD) detection during the early treatment phase has become an important stratification parameter in many childhood acute lymphoblastic leukaemia (ALL) treatment protocols. Here, we aimed to address the applicability of rearranged antigen‐receptor genes as potential MRD markers using real‐time quantitative polymerase chain reaction (RQ‐PCR) in a Swedish population‐based cohort. From 334 childhood ALL cases diagnosed during 2002–2006, we analysed 279 diagnostic samples (84%) by screening for rearranged immunoglobulin (IG) and T‐cell receptor (TCR) genes. Allele‐specific oligonucleotides were designed, and the sensitivity and quantitative level was determined for each target. Overall, clonal IG/TCR rearrangements were detected in 97% (236/244) of B‐cell precursor ALL (BCP ALL) and 94% (33/35) of T‐ALL. A sensitive RQ‐PCR analysis (≤10^?4) was obtained in 89% (216/244) of BCP ALL and in 74% (26/35) of T‐ALL, whereas two sensitive targets were only available in 47% (115/244) of BCP ALL and 29% (10/35) of T‐ALL cases. With the stratification threshold of ≥10^?3, which is applied in the current Nordic treatment protocol (NOPHO‐ALL 2008) for the identification of high‐risk patients, 93% of BCP ALL and 86% of T‐ALL reached this quantitative range by at least one target gene. Taken together, this national retrospective study demonstrates that an IG/TCR target for MRD monitoring can be identified in the majority of childhood ALL cases, whereas identification of a second sensitive target gene needs to be improved.     

Detailed immunophenotyping of B‐cell precursors in regenerating bone marrow of acute lymphoblastic leukaemia patients: implications for minimal residual disease detection

Flow cytometric detection of minimal residual disease (MRD) in children with B‐cell precursor acute lymphoblastic leukaemia (BCP‐ALL) requires immunophenotypic discrimination between residual leukaemic cells and B‐cell precursors (BCPs) which regenerate during therapy intervals. In this study, EuroFlow‐based 8‐colour flow cytometry and innovative analysis tools were used to first characterize the immunophenotypic maturation of normal BCPs in bone marrow (BM) from healthy children, resulting in a continuous multiparametric pathway including transition stages. This pathway was subsequently used as a reference to characterize the immunophenotypic maturation of regenerating BCPs in BM from children treated for BCP‐ALL. We identified pre‐B‐I cells that expressed low or dim CD34 levels, in contrast to the classical CD34^high pre‐B‐I cell immunophenotype. These CD34^−dim pre‐B‐I cells were relatively abundant in regenerating BM (11–85% within pre‐B‐I subset), while hardly present in healthy control BM (9–13% within pre‐B‐I subset; P = 0·0037). Furthermore, we showed that some of the BCP‐ALL diagnosis immunophenotypes (23%) overlapped with CD34^−dim pre‐B‐I cells. Our results indicate that newly identified CD34^−dim pre‐B‐I cells can be mistaken for residual BCP‐ALL cells, potentially resulting in false‐positive MRD outcomes. Therefore, regenerating BM, in which CD34^−dim pre‐B‐I cells are relatively abundant, should be used as reference frame in flow cytometric MRD measurements.     

Persistent MRD before and after allogeneic BMT predicts relapse in children with acute lymphoblastic leukaemia

Minimal residual disease (MRD) during early chemotherapy is a powerful predictor of relapse in acute lymphoblastic leukaemia (ALL) and is used in children to determine eligibility for allogeneic haematopoietic stem cell transplantation (HSCT) in first (CR1) or later complete remission (CR2/CR3). Variables affecting HSCT outcome were analysed in 81 children from the ANZCHOG ALL8 trial. The major cause of treatment failure was relapse, with a cumulative incidence of relapse at 5 years (CIR) of 32% and treatment‐related mortality of 8%. Leukaemia‐free survival (LFS) and overall survival (OS) were similar for HSCT in CR1 (LFS 62%, OS 83%, n = 41) or CR2/CR3 (LFS 60%, OS 72%, n = 40). Patients achieving bone marrow MRD negativity pre‐HSCT had better outcomes (LFS 83%, OS 92%) than those with persistent MRD pre‐HSCT (LFS 41%, OS 64%, P < 0·0001) or post‐HSCT (LFS 35%, OS 55%, P < 0·0001). Patients with B‐other ALL had more relapses (CIR 50%, LFS 41%) than T‐ALL and the main precursor‐B subtypes including BCR‐ABL1, KMT2A (MLL), ETV6‐RUNX1 (TEL‐AML1) and hyperdiploidy >50. A Cox multivariate regression model for LFS retained both B‐other ALL subtype (hazard ratio 4·1, P = 0·0062) and MRD persistence post‐HSCT (hazard ratio 3·9, P = 0·0070) as independent adverse prognostic variables. Persistent MRD could be used to direct post‐HSCT therapy.     

Outcome of children with newly diagnosed acute lymphoblastic leukemia treated with CCLG‐ALL 2008: The first nation‐wide prospective multicenter study in China

Acute lymphoblastic leukemia (ALL) is the most common malignancy among children. The trial Chinese Children Leukemia Group (CCLG)‐ALL 2008 was a prospective clinical trial designed to improve treatment outcome of childhood ALL through the first nation‐wide collaborative study in China. Totally 2231 patients were recruited from ten tertiary hospitals in eight cities. The patients were stratified according to clinical‐biological characteristics and early treatment response. Standard risk (SR) and intermediate risk (IR) groups were treated with a modified BFM based protocol, and there was 25%‐50% dose reduction during intensification phases in the SR group. Patients in high risk (HR) group received a more intensive maintenance treatment. Minimal residual disease (MRD) monitoring with treatment adjustment was performed in two hospitals (the MRD group). Complete remission (CR) was achieved in 2100 patients (94.1%). At five years, the estimate for overall survival (OS) and event‐free survival (EFS) of the whole group was 85.3% and 79.9%, respectively. The cumulative incidence of relapse (CIR) was 15.3% at five years. The OS, EFS and CIR for the SR group were 91.5%, 87.9%, and 9.7%, respectively. The outcome of the MRD group is better than the non‐MRD group (5y‐EFS: 82.4% vs 78.3%, P = .038; 5y‐CIR: 10.7% vs 18.0%, P < .001). Our results demonstrated that the large‐scale multicenter trial for pediatric ALL was feasible in China. Dose reduction in the SR group could achieve high EFS. MRD‐based risk stratification might improve the treatment outcome for childhood ALL.     

CD66c expression in B‐cell acute lymphoblastic leukemia: strength and weakness

Introduction: In B‐cell acute lymphoblastic leukemia (B‐ALL), testing at diagnosis for BCR/ABL1 gene rearrangements is mandatory for prognostic stratification and treatment decisions. Several diagnostic methods have been proposed using flow cytometry to identify BCR/ABL1⁺ B‐ALL. Methods: We evaluated expression of the myeloid antigen CD66c by flow cytometry in B‐ALL. We studied 94 patients with B‐ALL. The t(9;22)(q34;q11) or BCR/ABL1 rearrangement was detected by cytogenetic analysis or RT/PCR. Myeloid antigens CD66c, CD13, CD33, CD117, Myeloperoxidase, CD15 and CD65 were determined by flow cytometry. Results: Of these 94 cases, 17 (18%) cases displayed BCR/ABL1 gene rearrangements and 38 (40%) cases were CD66c positive. CD66c was the most common myeloid antigen expressed on malignant lymphoblasts. Its expression was correlated with BCR/ABL1 rearrangements (P = 0.0001): sensitivity 82%, specificity 69%, positive predictive value 37% and negative predictive value 95%. Co‐expression of CD66c⁺ CD13⁺ was more frequent in BCR/ABL1⁺ B‐ALL (29%) than BCR/ABL1^? cases (4%) (P = 0.0044). Some BCR/ABL1^? B‐ALL cases (including hyperdiploid or cases with normal karyotype) were CD66c positive (31%). Conclusion: CD66c expression is correlated, but not specifically, with BCR/ABL1 rearrangement. It would seem better to interpret the absence of CD66c expression with a lack of BCR/ABL1 rearrangement. This myeloid antigen could be interesting in the detection of minimal residual disease.     

The early achievement of measurable residual disease negativity in the treatment of adults with Philadelphia-negative B-cell acute lymphoblastic leukemia is a strong predictor for survival

The minimal or measurable residual disease (MRD) status following induction/consolidation chemotherapy is an important prognostic endpoint in adult patients with newly diagnosed acute lymphoblastic leukemia (ALL). However, the optimal time-point (TP) of MRD assessment and its impact on outcome remains unclear. We analyzed 215 patients with newly diagnosed Philadelphia negative B-cell ALL who received intensive chemotherapy, and had available MRD assessment by multicolor flow cytometry at two separate TPs. The median time to first TP (1TP) and second TP (2TP) were 24 and 110 days, respectively. At 1TP, 148 patients (68%) were MRD negative and 67 (32%) were positive. Of the 148 patients with negative MRD at 1TP, 147 (99%) maintained it through 2TP. Patients who were MRD negative at both TPs, early MRD responders, had the 3-year event-free survival (EFS), and overall survival (OS) rates of 65% and 76%, respectively. Patients with improved MRD status from positive to negative, late MRD responders, had lower 3-year EFS and OS rates, 42% and 58%, respectively (P = .001). Multivariate analysis showed that KMT2A (MLL) rearrangement and MRD positivity at 1TP were the only factors correlated with worse OS. In conclusion, the earlier achievement of MRD negative remission is a stronger prognostic factor for survival.     

Multiplex PCR for TCR delta rearrangements: a rapid and specific approach for the detection and identification of immature and mature rearrangements in ALL

The preferential occurrence of immature T-cell receptor (TCR) δ rearrangements (i.e. incomplete Dδ2-Dδ3 and Vδ2-Dδ3) in B-cell precursor acute lymphoblastic leukaemia (BCP ALL) and of predominantly mature rearrangements (incomplete Dδ2-Jδ1, complete Vδ1, Vδ2, Vδ3 to Jδ1) in T-lineage ALL prompted us to establish two separate multiplex PCR systems for the identification of clonal TCRδ rearrangements. PCR products of the expected size for the specific rearrangements were detectable from a dilution of 100–1000 clonal cells in 150 000 polyclonal cells. Both multiplex PCR systems were used to analyse samples from 86 childhood BCP ALLs and 30 T-lineage ALLs. The results of the multiplex PCRs were controlled by standard PCR analyses for the individual rearrangements and Southern blots, which were identical. Only immature TCRδ rearrangements were detected in BCP ALL (59%), whereas no rearrangement was found in the remaining BCP leukaemias, thus confirming the exclusive presence of immature TCRδ rearrangements in B-lineage cells. 50% of the T-lineage ALLs contained mature rearrangements, but no immature rearrangements were found. These two multiplex PCR techniques appear to be reliable and fast aids in the analysis of clonal TCRδ rearrangements in ALL.     

p185(BCR/ABL) has a lower sensitivity than p210(BCR/ABL) to the allosteric inhibitor GNF-2 in Philadelphia chromosome-positive acute lymphatic leukemia

Background

The t(9;22) translocation leads to the formation of the chimeric breakpoint cluster region/c-abl oncogene 1 (BCR/ABL) fusion gene on der22, the Philadelphia chromosome. The p185^BCR/ABL or the p210^BCR/ABL fusion proteins are encoded as a result of the translocation, depending on whether a “minor” or “major” breakpoint occurs, respectively. Both p185^BCR/ABL and p210^BCR/ABL exhibit constitutively activated ABL kinase activity. Through fusion to BCR the ABL kinase in p185^BCR/ABL and p210^BCR/ABL “escapes” the auto-inhibition mechanisms of c-ABL, such as allosteric inhibition. A novel class of compounds including GNF-2 restores allosteric inhibition of the kinase activity and the transformation potential of BCR/ABL. Here we investigated whether there are differences between p185^BCR/ABL and p210^BCR/ABL regarding their sensitivity towards allosteric inhibition by GNF-2 in models of Philadelphia chromosome-positive acute lymphatic leukemia.

Design and Methods

We investigated the anti-proliferative activity of GNF-2 in different Philadelphia chromosome-positive acute lymphatic leukemia models, such as cell lines, patient-derived long-term cultures and factor-dependent lymphatic Ba/F3 cells expressing either p185^BCR/ABL or p210^BCR/ABL and their resistance mutants.

Results

The inhibitory effects of GNF-2 differed constantly between p185^BCR/ABL and p210^BCR/ABL expressing cells. In all three Philadelphia chromosome-positive acute lymphatic leukemia models, p210^BCR/ABL-transformed cells were more sensitive to GNF-2 than were p185BCR/ABL-positive cells. Similar results were obtained for p185^BCR/ABL and the p210^BCR/ABL harboring resistance mutations.

Conclusions

Our data provide the first evidence of a differential response of p185^BCR/ABL- and p210^BCR/ABL- transformed cells to allosteric inhibition by GNF-2, which is of importance for the treatment of patients with Philadelphia chromosome-positive acute lymphatic leukemia.     

Current paradigms in the management of Philadelphia chromosome positive acute lymphoblastic leukemia in adults

Philadelphia chromosome‐positive (Ph‐positive) acute lymphoblastic leukemia (ALL) is a biologically, clinically, and genetically distinct subtype of precursor‐B ALL. The Ph chromosome, results from a reciprocal translocation of the ABL1 kinase gene on chromosome 9 to the breakpoint cluster region (BCR) gene on chromosome 22. Depending on the translocation breakpoint, typically a p210 BCR‐ABL1 or a p190 BCR‐ABL onc protein are generated; both are constitutively active tyrosine kinases that play a central role to alter signaling pathways of cell proliferation, survival, and self‐renewal, leading to leukemogenesis. In Ph‐positive ALL, the p190‐BCR‐ABL (minor [m]‐bcr) subtype is more frequent than the p210‐BCR‐ABL (major [M]‐bcr) subtype, commonly found in chronic myeloid leukemia. The Philadelphia chromosome is the most frequent recurrent cytogenetic abnormality in elderly patients with ALL. Its incidence increases with age, reaching ～50% in patients with ALL aged 60 years and over. Patients traditionally had a very poor outcome with chemotherapy, particularly if they do not undergo allogeneic hematopoietic cell transplantation (allo‐HCT) in first complete remission (CR1). With the availability of multiple tyrosine kinase inhibitors (TKI), the therapeutic armamentarium is expanding quickly. However, there is no consensus on how to best treat Ph‐positive ALL. With modern therapy, improved outcomes have led to the emergence of a number of controversies, including the need for intensive chemotherapy, the ideal TKI, and whether all eligible patients should receive an allo‐HSCT, and if so, what type. Here, we discuss these controversies in light of the available literature.     

Acute leukaemias of ambiguous lineage in children: characterization,prognosis and therapy recommendations

Acute leukaemias of ambiguous lineage (ALAL) represent a rare type of leukaemia, expressing both myeloid and lymphoid markers. This study retrospectively analyzed data from 92 children (biphenotypic n = 78, bilineal n = 6, lineage switch n = 8) with ALAL registered in the Berlin‐Frankfürt‐Münster (BFM) acute myeloid leukaemia (AML) and acute lymphoblastic leukaemia (ALL) studies between 1998 and 2006 (2·4% of all cases with acute leukaemia). Our cohort of ALAL patients was characterized by comparatively high median age (8·9 years), high median white blood cell count (14·9 × 10⁹/l), as well as frequent hyperleucocytosis (18·5%) and central nervous system involvement (24·1%). The most frequent cytogenetic abnormalities were ETV6/RUNX1 fusion (16%) and trisomy 8 (14·6%). Complete remission rate was significantly lower than in ALL‐BFM patients (91·8% vs. 99·1%, P < 0·001), but comparable to AML‐BFM patients (87·9%). Event‐free survival (EFS) and overall survival (OS) of ALAL patients were low, at 62 ± 5%. 5‐year probability of EFS was significantly worse than in ALL patients (80 ± 1%, P < 0·001), but better than for AML patients (49 ± 2%, P = 0·027). Our data suggest that an intensive therapy regimen including stem cell transplantation may be favourable for bilineal or lineage switch cases, whereas patients with ETV6/RUNX1 fusion, lymphoid morphology and patients with expression of cyCD22 and cyCD79a should be treated with an ALL‐directed therapy.