Clonal evolution in patients developing therapy-related myeloid neoplasms following autologous stem cell transplantation.

Clonal hematopoiesis (CH) denotes somatic mutations in genes related to myeloid neoplasms present at any variant allele frequency (VAF). Clonal hematopoiesis is associated with increasing age and with a factor 6 increase in the risk of developing therapy-related myeloid neoplasms (tMNs) following autologous stem cell transplantation (ASCT). However, the impact of specific mutations on progression from CH to tMN has yet to be unraveled, and it remains unclear whether mutations directly impact or even drive the development of tMN. We performed deep sequencing in longitudinal samples from a cohort of 12 patients with either multiple myeloma or lymphoma who developed tMN following ASCT. Nine patients had one or more mutations that could be tracked longitudinally. Seven patients had clonal expansion from time of ASCT to diagnosis of tMN. Of these, six patients had CH at VAF < 2% at baseline. The median VAF of non-DNMT3A clones increased from 1% (IQR 0.7%-10.0%) at time of ASCT to 37% (IQR 17%-47%) at tMN diagnosis (P = 0.002), while DNMT3A clones showed quiescent trajectories (P = 0.625). Our data provide evidence to support the hypothesis that the development of tMN following ASCT is likely instigated by CH present at VAFs as low as 0.5%, detectable years before tMN onset.

Exploring dyserythropoiesis in patients with myelodysplastic syndrome by imaging flow cytometry and machine-learning assisted morphometrics.

BACKGROUND: The hallmark of myelodysplastic syndrome (MDS) remains dysplasia in the bone marrow (BM). However, diagnosing MDS may be challenging and subject to inter-observer variability. Thus, there is an unmet need for novel objective, standardized and reproducible methods for evaluating dysplasia. Imaging flow cytometry (IFC) offers combined analyses of phenotypic and image-based morphometric parameters, for example, cell size and nuclearity. Hence, we hypothesized IFC to be a useful tool in MDS diagnostics. METHODS: Using a different-from-normal approach, we investigated dyserythropoiesis by quantifying morphometric features in a median of 5953 erythroblasts (range: 489-68,503) from 14 MDS patients, 11 healthy donors, 6 non-MDS controls with increased erythropoiesis, and 6 patients with cytopenia. RESULTS: First, we morphometrically confirmed normal erythroid maturation, as immunophenotypically defined erythroid precursors could be sequenced by significantly decreasing cell-, nuclear- and cytoplasm area. In MDS samples, we demonstrated cell size enlargement and increased fractions of macronormoblasts in late-stage erythroblasts (both p < .0001). Interestingly, cytopenic controls with high-risk mutational patterns displayed highly aberrant cell size morphometrics. Furthermore, assisted by machine learning algorithms, we reliably identified and enumerated true binucleated erythroblasts at a significantly higher frequency in two out of three erythroblast maturation stages in MDS patients compared to normal BM (both p = .0001). CONCLUSION: We demonstrate proof-of-concept results of the applicability of automated IFC-based techniques to study and quantify morphometric changes in dyserythropoietic BM cells. We propose that IFC holds great promise as a powerful and objective tool in the complex setting of MDS diagnostics with the potential for minimizing inter-observer variability.

Clonal hematopoiesis predicts development of therapy-related myeloid neoplasms post-autologous stem cell transplantation.

Therapy-related myeloid neoplasms (tMN) develop after exposure to cytotoxic and radiation therapy, and due to their adverse prognosis, it is of paramount interest to identify patients at high risk. The presence of clonal hematopoiesis has been shown to increase the risk of developing tMN. The value of analyzing hematopoietic stem cells harvested at leukapheresis before autologous stem cell transplantation (ASCT) with next-generation sequencing and immunophenotyping represents potentially informative parameters that have yet to be discovered. We performed a nested case-control study to elucidate the association between clonal hematopoiesis, mobilization potential, and aberrant immunophenotype in leukapheresis products with the development of tMN after ASCT. A total of 36 patients with nonmyeloid disease who were diagnosed with tMN after treatment with ASCT were included as case subjects. Case subjects were identified from a cohort of 1130 patients treated with ASCT and matched with 36 control subjects who did not develop tMN after ASCT. Case subjects were significantly poorer mobilizers of CD34+ cells at leukapheresis (P = .016), indicating that these patients possess inferior bone marrow function. Both clonal hematopoiesis (odds ratio, 5.9; 95% confidence interval, 1.8-19.1; P = .003) and aberrant expression of CD7 (odds ratio, 6.6; 95% confidence interval, 1.6-26.2; P = .004) at the time of ASCT were associated with an increased risk of developing tMN after ASCT. In conclusion, clonal hematopoiesis, present at low variant allele frequencies, and aberrant CD7 expression on stem cells in leukapheresis products from patients with nonmyeloid hematologic cancer hold potential for the early identification of patients at high risk of developing tMN after ASCT.

Unravelling the relevance of CLEC12A as a cancer stem cell marker in myelodysplastic syndrome.

Evidence of distinct disease propagating stem cells in myelodysplastic syndrome (MDS) has emerged in recent years. However, immunophenotypic characterization of these cancer stem cells remains sparse. In acute myeloid leukaemia (AML), we have previously described aberrant expression of the C-type lectin domain family 12, member A (CLEC12A) as a stable and reliable marker of leukaemia blasts and as a tool for assessing minimal residual disease. Furthermore, CLEC12A has been proposed as a promising marker of leukaemic stem cells in AML. The role of CLEC12A in MDS, however, remains to be elucidated. In this study, we found CLEC12A aberrantly expressed on the CD34+ CD38- cell compartment in 71% (22/31) of MDS patients, distributed across all Revised International Prognostic Scoring System risk groups. We showed that the CD34+ CD38- CLEC12A+ cells were indeed malignant and possessed functional stem cell properties in the long-term colony-initiating cell assay. As opposed to reported findings in AML, we showed that cancer stem cells from MDS samples derived from both CLEC12A positive and negative CD34+ CD38- subpopulations. Due to the absence of CLEC12A on normal haematopoietic stem cells, CLEC12A stem cell immunophenotyping may contribute to diagnosing and monitoring MDS patients and could furthermore add knowledge about disease propagating cells in MDS.

Autoimmune Hepatitis and Seronegative Hepatitis Associated With Myelodysplastic Syndrome in Children.

An association between hepatitis and aplastic anemia (AA) is known as hepatitis-associated AA, and is characterized by an acute attack of hepatitis followed by the development of AA. We report 2 clinical cases of acute seronegative hepatitis in which pancytopenia with mild dysplasia developed after 3 months; however, neither of our cases fulfilled the histological criteria of AA, but rather myelodysplastic syndrome. This novel association bears considerable resemblance to hepatitis-associated AA, and raises the question of whether hepatitis-associated dysmyelopoiesis should be included in the spectrum of hypocellular myelodysplastic syndrome.

Loss of B cells and their precursors is the most constant feature of GATA-2 deficiency in childhood myelodysplastic syndrome.

GATA-2 deficiency was recently described as common cause of overlapping syndromes of immunodeficiency, lymphedema, familiar myelodysplastic syndrome or acute myeloid leukemia. The aim of our study was to analyze bone marrow and peripheral blood samples of children with myelodysplastic syndrome or aplastic anemia to define prevalence of the GATA2 mutation and to assess whether mutations in GATA-2 transcription factor exhibit specific immunophenotypic features. The prevalence of a GATA2 mutation in a consecutively diagnosed cohort of children was 14% in advanced forms of myelodysplastic syndrome (refractory anemia with excess blasts, refractory anemia with excess blasts in transformation, and myelodysplasia-related acute myeloid leukemia), 17% in refractory cytopenia of childhood, and 0% in aplastic anemia. In GATA-2-deficient cases, we found the most profound B-cell lymphopenia, including its progenitors in blood and bone marrow, which correlated with significantly diminished intronRSS-Kde recombination excision circles in comparison to other myelodysplastic syndrome/aplastic anemia cases. The other typical features of GATA-2 deficiency (monocytopenia and natural killer cell lymphopenia) were less discriminative. In conclusion, we suggest screening for GATA2 mutations in pediatric myelodysplastic syndrome, preferentially in patients with impaired B-cell homeostasis in bone marrow and peripheral blood (low number of progenitors, intronRSS-Kde recombination excision circles and naïve cells).

Rare MLL-ELL fusion transcripts in childhood acute myeloid leukemia-association with young age and myeloid sarcomas?

BACKGROUND: The chromosomal translocation t(11;19)(q23;p13) with a breakpoint within subband 19p13.1 is found mainly in acute myeloid leukemia (AML) and results in the MLL-ELL fusion gene. Variations in the structure of MLL-ELL seem to influence the leukemogenic potency of the fusion in vivo and may lie behind differences in clinical features. The number of cases reported so far is very limited and the addition of more information about MLL-ELL variants is essential if the possible clinical significance of rare fusions is to be determined. CASE PRESENTATION: Cytogenetic and molecular genetic analyses were done on the bone marrow cells of a 20-month-old boy with an unusual form of myelomonocytic AML with multiple myeloid sarcomas infiltrating bone and soft tissues. The G-banding analysis together with FISH yielded the karyotype 47,XY, +6,t(8;19;11)(q24;p13;q23). FISH analysis also demonstrated that MLL was split. RNA-sequencing showed that the translocation had generated an MLL-ELL chimera in which exon 9 of MLL (nt 4241 in sequence with accession number NM_005933.3) was fused to exon 6 of ELL (nt 817 in sequence with accession number NM_006532.3). RT-PCR together with Sanger sequencing verified the presence of the above-mentioned fusion transcript. CONCLUSIONS: Based on our findings and information on a few previously reported patients, we speculate that young age, myelomonoblastic AML, and the presence of extramedullary disease may be typical of children with rare MLL-ELL fusion transcripts.

t(6;9)(p22;q34)/DEK-NUP214-rearranged pediatric myeloid leukemia: an international study of 62 patients.

Acute myeloid leukemia with t(6;9)(p22;q34) is listed as a distinct entity in the 2008 World Health Organization classification, but little is known about the clinical implications of t(6;9)-positive myeloid leukemia in children. This international multicenter study presents the clinical and genetic characteristics of 62 pediatric patients with t(6;9)/DEK-NUP214-rearranged myeloid leukemia; 54 diagnosed as having acute myeloid leukemia, representing <1% of all childhood acute myeloid leukemia, and eight as having myelodysplastic syndrome. The t(6;9)/DEK-NUP214 was associated with relatively late onset (median age 10.4 years), male predominance (sex ratio 1.7), French-American-British M2 classification (54%), myelodysplasia (100%), and FLT3-ITD (42%). Outcome was substantially better than previously reported with a 5-year event-free survival of 32%, 5-year overall survival of 53%, and a 5-year cumulative incidence of relapse of 57%. Hematopoietic stem cell transplantation in first complete remission improved the 5-year event-free survival compared with chemotherapy alone (68% versus 18%; P<0.01) but not the overall survival (68% versus 54%; P=0.48). The presence of FLT3-ITD had a non-significant negative effect on 5-year overall survival compared with non-mutated cases (22% versus 62%; P=0.13). Gene expression profiling showed a unique signature characterized by significantly higher expression of EYA3, SESN1, PRDM2/RIZ, and HIST2H4 genes. In conclusion, t(6;9)/DEK-NUP214 represents a unique subtype of acute myeloid leukemia with a high risk of relapse, high frequency of FLT3-ITD, and a specific gene expression signature.

Comparison of horse and rabbit antithymocyte globulin in immunosuppressive therapy for refractory cytopenia of childhood.

Refractory cytopenia of childhood is the most common subtype of myelodysplastic syndrome in children. In this study, we compared the outcome of immunosuppressive therapy using horse antithymocyte globulin (n=46) with that using rabbit antithymocyte globulin (n=49) in 95 patients with refractory cytopenia of childhood and hypocellular bone marrow. The response rate at 6 months was 74% for horse antithymocyte globulin and 53% for rabbit antithymocyte globulin (P=0.04). The inferior response in the rabbit antithymocyte globulin group resulted in lower 4-year transplantation-free (69% versus 46%; P=0.003) and failure-free (58% versus 48%; P=0.04) survival rates in this group compared with those in the horse antithymocyte globulin group. However, because of successful second-line hematopoietic stem cell transplantation, overall survival was comparable between groups (91% versus 85%; P=ns). The cumulative incidence of relapse (15% versus 9%; P=ns) and clonal evolution (12% versus 4%; P=ns) at 4 years was comparable between groups. Our results suggest that the outcome of immunosuppressive therapy with rabbit antithymocyte globulin is inferior to that of horse antithymocyte globulin. Although immunosuppressive therapy is an effective therapy in selected patients with refractory cytopenia of childhood, the long-term risk of relapse or clonal evolution remains. (ClinicalTrial.gov identifiers: NCT00662090).

Fusion of ZMYND8 and RELA genes in acute erythroid leukemia.

Acute erythroid leukemia was diagnosed in a 4-month-old boy. Cytogenetic analysis of bone marrow (BM) cells showed a t(11;20)(p11;q11) translocation. RNA extracted from the BM was sequenced and analyzed for fusion transcripts using the software FusionMap. A ZMYND8-RELA fusion was ranked first. RT-PCR and direct sequencing verified the presence of an in frame ZMYND8-RELA chimeric transcript. Fluorescence in situ hybridization showed that the ZMYND8-RELA was located on the p12 band of der(11); therefore a cytogenetically invisible pericentric inversion in chromosome 11 must have taken place besides the translocation. The putative ZMYND8-RELA fusion protein contains the Zinc-PHD finger domain, a bromodomain, a PWWP domain, a MYND type of zinc finger of ZMYND8, and the entire RELA protein, indicating that it might act leukemogenically by influencing several cellular processes including the NF-kappa-B pathway.

Efficacy of anti-IL-1 treatment in Majeed syndrome.

BACKGROUND AND OBJECTIVE: Majeed syndrome is an autosomal recessive disorder characterised by the triad of chronic recurrent multifocal osteomyelitis, congenital dyserythropoietic anaemia and a neutrophilic dermatosis that is caused by mutations in LPIN2. Long-term outcome is poor. This is the first report detailing the treatment of Majeed syndrome with biological agents and demonstrates clinical improvement with IL-1blockade. METHODS: We describe the clinical presentation, genetic analysis, cytokine profiles and response to biological therapy in two brothers with Majeed syndrome. RESULTS: Both boys were homozygous for a novel 2-base pair deletion in LPIN2 (c.1312_1313delCT; p.Leu438fs+16X), confirming the diagnosis. Their bone disease and anaemia were refractory to treatment with corticosteroids. Both siblings had elevated proinflammatory cytokines in their serum, including tumour necrosis factor α (TNF-α), however a trial of the TNF inhibitor etanercept resulted in no improvement. IL-1 inhibition with either a recombinant IL-1 receptor antagonist (anakinra) or an anti-IL-1ß antibody (canakinumab) resulted in dramatic clinical and laboratory improvement. CONCLUSIONS: The differential response to treatment with TNF-α or IL-1 blocking agents sheds light into disease pathogenesis; it supports the hypothesis that Majeed syndrome is an IL-1ß dependent autoinflammatory disorder, and further underscores the importance of IL-1 in sterile bone inflammation.

Morphological differentiation of severe aplastic anaemia from hypocellular refractory cytopenia of childhood: reproducibility of histopathological diagnostic criteria.

AIMS: To evaluate the reproducibility and reliability of the histomorphological criteria differentiating severe aplastic anaemia (SAA) and hypoplastic refractory cytopenia of childhood (RCC), the most frequently acquired hypocellular bone marrow conditions of childhood. METHODS AND RESULTS: We performed a double-blind interobserver study of 100 different cases of SAA and RCC among seven haematopathologists of the European Working Group of MDS in Childhood (EWOG-MDS) and the German SAA study. Cases with foci of typical myelodysplastic syndrome (MDS) morphology, such as patchy erythropoiesis with defective maturation, in an otherwise highly hypocellular or adipocytic bone marrow were classified as having RCC. Bone marrow samples without a patchy distribution, few scattered myeloid cells or haematopoietic aplasia were diagnosed as SAA. In only four of 100 cases did the reference pathologists not reach agreement regarding classification as SAA or RCC. The kappa index was 0.79. CONCLUSIONS: Our results show that the vast majority of SAA and RCC cases can be reliably differentiated by morphological means alone. A clear differentiation between SAA and RCC at presentation is mandatory for optimizing therapy strategies, and might be responsible for the fact that, in the German childhood SAA study, the probability of developing clonal disease after immunosuppressive therapy has dropped to 3%.

Report from the European Myeloma Network on interphase FISH in multiple myeloma and related disorders.

The European Myeloma Network has organized two workshops on fluorescence in situ hybridization in multiple myeloma. The first aimed to identify specific indications and consensus technical approaches of current practice. A second workshop followed a quality control exercise in which 21 laboratories analyzed diagnostic cases of purified plasma cells for recurrent abnormalities. The summary report was discussed at the EHA Myeloma Scientific Working Group Meeting 2010. During the quality control exercise, there was acceptable agreement on more than 1,000 tests. The conclusions from the exercise were that the primary clinical applications for FISH analysis were for newly diagnosed cases of MM or frank relapse cases. A range of technical recommendations included: 1) material should be part of the first draw of the aspirate; 2) samples should be sent at suitable times to allow for the lengthy processing procedure; 3) most importantly, PCs must be purified or specifically identified; 4) positive cut-off levels should be relatively conservative: 10% for fusion or break-apart probes, 20% for numerical abnormalities; 5) informative probes should be combined to best effect; 6) in specialist laboratories, a single experienced analyst is considered adequate; 7) at least 100 PC should be scored; 8) essential abnormalities to test for are t(4;14), t(14;16) and 17p13 deletions; 9) suitable commercial probes should be available for clinically relevant abnormalities; 10) the clinical report should be expressed clearly and must state the percentage of PC involved and the method used for identification; 11) a retrospective European based FISH data bank linked to clinical data should be generated; and 12) prospective analysis should be centralized for upcoming trials based on the recommendations made. The European Myeloma Network aims to build on these recommendations to establish standards for a common European data base to define subgroups with prognostic significance.

Cytogenetic findings in adult secondary acute myeloid leukemia (AML): frequency of favorable and adverse chromosomal aberrations do not differ from adult de novo AML.

During a 15-year period, 161 adult patients were diagnosed with secondary acute myeloid leukemia (s-AML) in the region of Southern Denmark. In 73 patients, the AML diagnosis was preceded by myelodysplastic syndrome (MDS-AML), in 31 patients by an antecedent hematologic disease, and in 57 patients by treatment with chemotherapy and/or irradiation (t-AML). Cytogenetic analysis was carried out in 93%, of which 61% had clonal chromosome aberrations. MDS-AML correlated to a normal karyotype (P < 0.001). t-AML correlated to abnormal clones with numerical and structural aberrations (P = 0.03), five or more unrelated aberrations (P = 0.03), marker chromosomes (P = 0.006), abnormal mitoses only (P = 0.01), female sex (P < 0.001), and -7 (P = 0.006). Centromeric breakage correlated to a complex karyotype (P = 0.01). The frequencies of aberrations in s-AML patients were compared with an age-matched group of de novo AML patients diagnosed in the same area and period. In this comparison, s-AML only correlated to -7 (P = 0.02). In 42 patients, we found that MDS patients with an abnormal karyotype were more likely to show cytogenetic evolution during progression to AML than MDS patients with a normal karyotype (P = 0.01). We conclude that population-based cytogenetic studies of adult s-AML and age- and sex-matched de novo AML show comparable distributions of chromosome abnormalities.

Complex karyotype newly defined: the strongest prognostic factor in advanced childhood myelodysplastic syndrome.

To identify cytogenetic risk factors predicting outcome in children with advanced myelodysplastic syndrome, overall survival of 192 children prospectively enrolled in European Working Group of Myelodysplastic Syndrome in Childhood studies was evaluated with regard to karyotypic complexity. Structurally complex constitutes a new definition of complex karyotype characterized by more than or equal to 3 chromosomal aberrations, including at least one structural aberration. Five-year overall survival in patients with more than or equal to 3 clonal aberrations, which were not structurally complex, did not differ from that observed in patients with normal karyotype. Cox regression analysis revealed the presence of a monosomal and structurally complex karyotype to be strongly associated with poor prognosis (hazard ratio = 4.6, P < .01). Notably, a structurally complex karyotype without a monosomy was associated with a very short 2-year overall survival probability of only 14% (hazard ratio = 14.5; P < .01). The presence of a structurally complex karyotype was the strongest independent prognostic marker predicting poor outcome in children with advanced myelodysplastic syndrome.

Identification of translocation products but not K-RAS mutations in memory B cells from patients with multiple myeloma.

BACKGROUND: Several laboratories have shown that cells with a memory B-cell phenotype can have the same clonotype as multiple myeloma tumor cells. DESIGN AND METHODS: The aim of this study was to determine whether some memory B cells have the same genetic alterations as their corresponding multiple myeloma malignant plasma cells. The methodology included sorting multiple myeloma or memory B cells into RNA stabilizing medium for generation of subset-specific polymerase chain reaction complementary DNA libraries from one or 100 cells. RESULTS: Cells with the phenotype of tumor plasma cells (CD38(++)CD19(-)CD45(-/+)CD56(-/+/++)) or memory B cells (CD38(-)/CD19(+)/CD27(+)) were isolated by flow activated cell sorting. In samples from all four patients with multiple myeloma and from two of the three with monoclonal gammopathy of undetermined significance, we identified memory B cells expressing multiple myeloma-specific oncogenes (FGFR3; IGH-MMSET; CCND1 high) dysregulated by an IGH translocation in the respective tumor plasma cells. By contrast, in seven patients with multiple myeloma, each of whom had tumor plasma cells with a K-RAS61 mutation, a total of 32,400 memory B cells were analyzed using a sensitive allele-specific, competitive blocker polymerase chain reaction assay, but no K-RAS mutations were identified. CONCLUSIONS: The increased expression of a specific "early" oncogene of multiple myeloma (monoclonal gammopathy of undetermined significance) in some memory B cells suggests that dysregulation of the oncogene occurs in a precursor B-cell that can generate memory B cells and transformed plasma cells. However, if memory B cells lack "late" oncogene (K-RAS) mutations but express the "early" oncogene, they cannot be involved in maintaining the multiple myeloma tumor, but presumably represent a clonotypic remnant that is only partially transformed.

Clinical and cytogenetic features of a population-based consecutive series of 285 pediatric T-cell acute lymphoblastic leukemias: rare T-cell receptor gene rearrangements are associated with poor outcome.

Clinical characteristics and cytogenetic aberrations were ascertained and reviewed in a population-based consecutive series of 285 pediatric T-cell acute lymphoblastic leukemias (T-ALLs) diagnosed between 1992 and 2006 in the Nordic countries. Informative karyotypic results were obtained in 249 (87%) cases, of which 119 (48%) were cytogenetically abnormal. Most (62%) of the aberrant T-ALLs were pseudodiploid. Structural changes were more common than numerical ones; 86% displayed at least one structural abnormality and 41% at least one numerical anomaly. The most frequent abnormalities were T-cell receptor (TCR) gene rearrangements (20%) [TCR;11p13 (10%), TCR;10q24 (3%), TCR;other (8%)], del(9p) (17%), +8 (14%), del(6q) (12%), and 11q23 rearrangements (6%). The TCR;other group comprised the rare rearrangements t(X;14)(p11;q11), t(X;7)(q22;q34), t(1;14)(p32;q11), ins(14;5)(q11;q?q?), inv(7)(p15q34), t(8;14)(q24;q11), t(7;11)(q34;p15), and t(12;14)(p13;q11). The clinical characteristics of this Nordic patient cohort agreed well with previous larger series, with a median age of 9.0 years, male predominance (male/female ratio 3.1), median white blood cell (WBC) count of 66.5 x 10(9)/l, and a high incidence of mediastinal mass and central nervous system involvement (59% and 9.5%, respectively). These features did not differ significantly among the various genetic subgroups. 5-year event-free survival (EFS) and overall survival for all patients were 0.61 (+/-0.03) and 0.67 (+/-0.03), respectively. In a multivariate analysis, two factors affected negatively the EFS, namely a WBC count of > or =200 x 10(9)/l (P < 0.001) and the presence of rare TCR rearrangements (P = 0.001). In conclusion, in this large series of childhood T-ALLs from the Nordic countries, the cytogenetic findings were not associated with risk of therapy failure with the exception of the TCR;other group. However, further prospective and collaborative investigations of this genetically heterogeneous entity are needed to confirm these results.

Outcome of ETV6/RUNX1-positive childhood acute lymphoblastic leukaemia in the NOPHO-ALL-1992 protocol: frequent late relapses but good overall survival.

The prognostic impact of t(12;21)(p13;q22) [ETV6/RUNX1 fusion] in paediatric acute lymphoblastic leukaemia (ALL) has been extensively debated, particularly with regard to the frequency of late relapses and appropriate treatment regimens. We have retrospectively collected 679 ALLs with known ETV6/RUNX1 status, as ascertained by fluorescence in situ hybridization or reverse-transcription polymerase chain reaction, treated according to the Nordic Society of Paediatric Haematology and Oncology -ALL-1992 protocol. The assigned risk groups/treatment modalities for the 171 (25%) patients with t(12;21)-positive ALLs were 74 (43%) standard risk, 71 (42%) intermediate risk and 26 (15%) high risk. The 5- and 10-year event-free survival (EFS) of the 171 patients was 80% and 75% respectively, with no significant differences among the three risk groups. Most of the relapses occurred in boys and were late, with almost 50% of all relapses occurring > or = 5 years after diagnosis. Of all relapses after 6 years, 80% occurred in the t(12;21)-positive group. The overall survival was 94% at 5 years and 88% at 10 years; thus, the treatment of patients in second or later remission is usually successful. As yet, there is no reliable plateau in the EFS curve, a fact that raises the question as to when the prognostic ramifications of ALLs harbouring ETV6/RUNX1 should be evaluated.

Clinical and cytogenetic features of pediatric dic(9;20)(p13.2;q11.2)-positive B-cell precursor acute lymphoblastic leukemias: a Nordic series of 24 cases and review of the literature.

Although dic(9;20)(p13.2;q11.2) is a characteristic abnormality in childhood B-cell precursor acute lymphoblastic leukemias (BCP ALL), little is known about its clinical impact or the type and frequency of additional aberrations it may occur together with. We here review the clinical and cytogenetic features of a Nordic pediatric series of 24 patients with dic(9;20)-positive BCP ALL diagnosed 1996-2006, constituting 1.3% of the BCP ALL, as well as 47 childhood cases from the literature. Consistent immunophenotypic features of the Nordic cases included positivity for HLA-DR, CD10, CD19, CD20, and CD22 and negativity for T-cell and myeloid markers; no detailed immunophenotypes were reported for the previously published cases. In the entire cohort of 71 cases, the modal chromosome distribution was 45 (62%), 46 (21%), 47 (7%), 48 (4%), 49 (3%), 44 (1%), and 50 (1%). Additional changes were present in 63%, the most frequent of which were homozygous loss of CDKN2A (33%) and gains of chromosomes 21 (28%) and X (10%). The median patient age was 3 years, the female/male ratio was 2.0, the median white blood cell count was 24 x 10(9)/l, 11% had central nervous system involvement, and 5% had a mediastinal mass at diagnosis. Risk group stratification was nonstandard risk in 79%. The event-free survival and overall survival at 5 years for the 24 Nordic cases was 0.62 and 0.82, respectively. Thus, although relapses are quite common, postrelapse treatment of many patients is successful.