Pediatric T-cell Lymphoblastic Lymphoma Research Articles

NOTCH1 fusions in pediatric T-cell lymphoblastic lymphoma: Ahigh-risk subgroup with CCL17 (TARC) levels as diagnostic biomarker.

Twenty percent of children with T-cell lymphoblastic lymphoma (T-LBL) will relapse and have an extremely poor outcome. Currently, we can identify a genetically low-risk subgroup in pediatric T-LBL, yet these high-risk patients who need intensified or alternative treatment options remain undetected. Therefore, there is an urgent need to recognize these high-risk T-LBL patients through identification of molecular characteristics and biomarkers. By using RNA sequencing which was performed in 29/49 T-LBL patients who were diagnosed in the Princess Maxima Center for Pediatric Oncology between 2018 and 2023, we discovered a previously unknown high-risk biological subgroup of children with T-LBL. This subgroup is characterized by NOTCH1 gene fusions, found in 21% of our T-LBL cohort (6/29). All patients presented with a large mediastinal mass, pleural/pericardial effusions, and absence of blasts in the bone marrow, blood, and central nervous system. Blood CCL17 (C-C Motif Chemokine Ligand 17, TARC) levels were measured at diagnosis in 26/29 patients, and all six patients with NOTCH1 gene fusions patients exclusively expressed highly elevated blood CCL17 levels, defining a novel and previously not known clinically relevant biomarker for T-cell lymphoblastic lymphoma. Four out of these six patients relapsed during therapy, a fifth developed a therapy-related acute myeloid leukemia during maintenance therapy. These data indicate that T-LBL patients with a NOTCH1 fusion have a high risk of relapse which can be easily identified using a blood CCL17 screening at diagnosis. Further molecular characterization through NOTCH1 gene fusion analysis offers these patients the opportunity for treatment intensification or new treatment strategies.

A New t(7;9)(p12;q34) Involving NOTCH1 and IKZF1 in Pediatric T-Cell Lymphoblastic Lymphoma

Background Notch1 pathway activation is demonstrated in approximately 50% of T-cell acute lymphoblastic leukemias/lymphomas (T-ALL/LL) mainly by the presence of activating somatic mutations of NOTCH1 involving homodimerization and/or PEST (proline, glutamic acid, serine, threonine) domains. The oncogenic role of NOTCH1 was however primarily described with the characterization of the recurrent although rare t(7;9)(q34;q34). By positioning the coding region of the intracellular part of Notch1 (ICN1) under the control of the TCR beta-gene promoter, this translocation generates a truncated Notch1 receptor resulting in constitutive activation of the Notch1 pathway, independent of ligand binding. In murine models ICN1 is much more pro-oncogenic than NOTCH1 activating mutations. While several retrospective studies identified NOTCH1 activating mutations as an independent good-prognostic factor in human T-ALL/LL, search for truncated ICN1 in NOTCH1 wild-type patients was usually not performed/considered. Aim To describe and characterize a new translocation in a pediatric patient with T-LL. Method Somatic cytogenetics of blastic T-cells from diagnosis was explored by conventional karyotype. A specific fluorescence in situ hybridization (FISH) Breakapart probe was designed to explore the NOTCH1 locus on chromosome 9q34. Targeted locus amplification based sequencing (TLA) using genomic DNA was used to confirm/determine the partners involved in the new fusion found. Targeted RNA-sequencing using the Illumina TruSight RNA Fusion Panel was used to determine the putative transcript produced by the fusion. Results The patient, a 14-year-old young female, was diagnosed with stage 3 T-LL characterized by a large mediastinal mass with massive pleural effusion. Flow cytometry demonstrated a CD7+, CD1a+, CD4+/CD8+ double positive phenotype corresponding to EGIL type III T-LL. Conventional karyotype on T-lymphoblastic cells showed two clonal abnormalities, a deletion del(6)(q13q22) and a translocation t(7;9)(p12;q34) in 10 metaphases analyzed. Involvement of NOTCH1 in this new t(7;9)(p12;q34) was confirmed by molecular cytogenetics using a FISH Breakapart probe targeting the NOTCH1 locus. Targeted locus amplification based sequencing (TLA) revealed IKZF1 as the fusion partner involved in this new fusion. DNA sequencing revealed a predictive fusion between the intracellular domain of NOTCH1 (ICN1; breakpoint in intron 26 (NM_017617.5)) and IKF1 (breakpoint in intron 5 (NM_006060)). The targeted RNA-sequencing performed on the pleural effusion confirmed an in frame NOTCH1-IKZF1 fusion transcript. Sequencing of exons 26-27 and 34 of NOTCH1 showed wild-type alleles. After a swift response to the induction phase, the patient is in complete remission one year after completing her treatment according to the EuroLB-02 protocol. Summary/perspectives This new t(7;9)(p12;q34) involving ICN1 illustrates the importance to look for ICN1 more extensively in parallel to NOTCH1/FBXW7 mutations in the screening of Notch1 activation pathway in T-ALL/LL specially in the event of a stratification on Notch1 status for treatment. As both NOTCH1 and IKZF1 are major actors of normal T-cell differentiation/proliferation, the oncogenic role of the fusion NOTCH1::IKZF1 in T-ALL/LL deserves a better understanding in a larger population and will be further explored.

17th International Conference on Malignant Lymphoma, Palazzo dei Congressi, Lugano, Switzerland, 13 - 17 June, 2023.

Introduction: Mature B-cell non-Hodgkin's lymphoma (MB-NHL) and T-cell lymphoblastic lymphoma (T-LBL) account for ∼50% and ∼20%, respectively, among the different pediatric NHL entities. Our understanding of the genetic lesions and profiling of these patients may help to improve the clinical management of patients with these lymphomas. The aim of this study is to analyze the mutational status and the associations between genetic features and treatment outcomes in the Chinese pediatric lymphoma cohort. Methods: A total of 207 patients treated at multiple clinical centers of the Chinese Children's Lymphoma Collaborative Group (CNCL) from 2017 to 2023 were included in this retrospective study. Targeted next-generation sequencing (t-NGS) with a panel of lymphoma-related genes was performed on tumor samples collected at the time of initial diagnosis and at tumor of refractory or relapse (r/r), and the correlations of somatic mutations with survival rates as well as with relapse and other clinical factors were analyzed. Results: A total of 136 driver genes with somatic mutations were detected in the entire cohort. In 133 pediatric MB-NHL patients, the most frequently mutated genes from 77 initially diagnostic samples were ID3 (52%), TP53 (47%), CCND3 (30%), ARID1A (29%), and DDX3X (27%) (Figure 1a). In 56 r/r samples, the most commonly mutated genes were TP53 (84%), followed by ID3 (59%), ARID1A (41%), CCND3 (32%), and DDX3X (25%) (Figure 1b). TP53 mutation was significantly more frequent in r/r samples than that in initially diagnostic samples (p < 0.001) and patients with TP53 mutations had poor survival (log-rank p = 0.0013, Figure 1c). Among patients treated with chimeric antigen receptor T-cell (CAR-T) therapy, those with ARID1A mutations exhibited poorer response to CAR-T treatment and shorter overall survival compared with the patients without such mutations (mOS = 180 days, log-rank p = 0.00081, Figure 1d). In 74 pediatric T-LBL patients,the most commonly mutated genes were NOTCH1 (50%), followed by FBXW7 (26%), JAK1 (16%), NRAS (16%), and JAK3 (11%) (Figure 1e). Genes in the JAK signaling pathway were more frequently mutated in Chinese patients than the corresponding western patients, such as JAK1 (16% vs. 2%) and JAK3 (11% vs. 5%). Further analysis showed that the incidence of NOTCH1 (68% vs. 27%) and FBXW7 (37% vs. 12%) mutations in patient group with initial remission (n = 41) was significantly higher than that in patient group with r/r T-LBL (n = 33) (p = 0.005, p = 0.036, respectively, Figure 1f), indicating that NOTCH1 and FBXW7mutations were associated with good prognosis. Keywords: diagnostic and prognostic biomarkers, immunotherapy, non-Hodgkin (pediatric, adolescent, and young adult) No conflicts of interests pertinent to the abstract.

Comprehensive view on genetic features, therapeutic modalities and prognostic models in adult T-cell lymphoblastic lymphoma.

Adult T-cell lymphoblastic lymphoma (T-LBL) is a rare and aggressive subtype of non-Hodgkin's lymphoma that differs from pediatric T-LBL and has a worse prognosis. Due to its rarity, little is known about the genetic and molecular characteristics, optimal treatment modalities, and prognostic factors of adult T-LBL. Therefore, we summarized the existing studies to comprehensively discuss the above issues in this review. Genetic mutations of NOTCH1/FBXW7, PTEN, RAS, and KMT2D, together with abnormal activation of signaling pathways, such as the JAK-STAT signaling pathway were described. We also discussed the therapeutic modalities. Once diagnosed, adult T-LBL patients should receive intensive or pediatric acute lymphoblastic leukemia regimen and central nervous system prophylaxis as soon as possible, and cranial radiation-free protocols are appropriate. Mediastinal radiotherapy improves clinical outcomes, but adverse events are of concern. Hematopoietic stem cell transplantation may be considered for adult T-LBL patients with high-risk factors or those with relapsed/refractory disease. Besides, several novel prognostic models have been constructed, such as the 5-miRNAs-based classifier, 11-gene-based classifier, and 4-CpG-based classifier, which have presented significant prognostic value in adult T-LBL.

Design of a targeted next-generation DNA sequencing panel for pediatric T-cell lymphoblastic lymphoma to unravel biology and optimize treatment.

Low incidence and molecular heterogeneity of pediatric T-cell lymphoblastic lymphoma (T-LBL) require an international, large-scale effort to identify novel clinical biomarkers. The ongoing international clinical trial LBL2018 (NCT04043494) represents an ideal opportunity to implement a common analytic approach. Targeted next-generation sequencing is well-suited for this purpose; however, selection of relevant target genes for T-LBL remains subject of ongoing debates. Our group has recently designed and evaluated a first target panel of 80 candidate genes for T-LBL. The present study aimed at developing a novel optimized gene panel for large-scale application and to promote an international agreement on a common core panel. Small sequence variants obtained from our former study were systematically analyzed and classified with regards to pathogenic relevance, to prioritize candidate genes. Additional genes were curated from literature and online databases for a more comprehensive analysis of relevant functions and signaling pathways. The new target panel TGP-T-LBL entails 84 candidate genes which are key actors in NOTCH, PI3K-AKT, JAK-STAT, RAS signaling, epigenetic regulation, transcription, DNA repair, cell cycle regulation, and ribosomal function. From our former gene panel, 35 out of 80 candidate genes were selected for the novel panel. Forty-six out of 84 genes are currently being analyzed in the ongoing international trial LBL2018. Exploratory analysis of prognostic relevance on mutation-level suggested a potential association of PIK3CA variants c.1624G>A(p.Glu542Lys) and c.1633G>A(p.Glu545Lys) to occurrence of relapse, emphasizing particular relevance of mutation analysis in PI3K-AKT signaling. Our approach promotes comprehensive and clinically relevant mutational profiling of pediatric T-LBL.

High Prevalence of Constitutional Mismatch Repair Deficiency in a Pediatric T-cell Lymphoblastic Lymphoma Cohort.

This study describes the clinical characteristics of a complete Dutch T-cell lymphoblastic lymphoma (T-LBL) cohort, including second primary malignancies and comorbidities. We show that over 10% of patients in this complete T-LBL cohort have been diagnosed with a cancer predisposition syndrome (CPS), consisting almost exclusively of constitutional mismatch repair deficiency (CMMRD). The clinical characteristics of sporadic T-LBL patients were compared with T-LBL patients that have been diagnosed with CMMRD. This shows that disease presentation is comparable but that disease localization in CMMRD patients might be more localized. The percentage of CPS seems reliable considering the completeness of the cohort of Dutch T-LBL patients and might even be an underestimation (possibility of undiagnosed CPS patients in cohort). As the frequency of an underlying predisposition syndrome among T-LBL patients may be underestimated at present, we advocate for screening all pediatric T-LBL patients for the presence of germline mutations in mismatch repair genes.

Integrative genomic analysis of pediatric T-cell lymphoblastic lymphoma reveals candidates of clinical significance

AbstractT-cell lymphoblastic lymphoma (T-LBL) is a heterogeneous malignancy of lymphoblasts committed to T-cell lineage. The dismal outcomes (15%-30%) after T-LBL relapse warrant establishing risk-based treatment. To our knowledge, this study presents the first comprehensive, systematic, integrated, genome-wide analysis including relapsed cases that identifies molecular markers of prognostic relevance for T-LBL. NOTCH1 was identified as the putative driver for T-LBL. An activated NOTCH/PI3K-AKT signaling axis and alterations in cell cycle regulators constitute the core oncogenic program for T-LBL. Mutated KMT2D was identified as a prognostic marker. The cumulative incidence of relapse was 47% ± 17% in patients with KMT2D mutations, compared with 14% ± 3% in wild-type KMT2D. Structural analysis of the mutated domains of KMT2D revealed a plausible impact on structure and functional consequences. These findings provide new insights into the pathogenesis of T-LBL, including high translational potential. The ongoing LBL 2018 trial (www.clinicaltrials.gov #NCT04043494) allows for prospective validation and subsequent fine tuning of the stratification criteria for T-LBL risk groups to improve survival of pediatric patients.

T(9;17)染色体異常を有した小児Tリンパ芽球性リンパ腫の1例

t(9;17)染色体異常を有した小児Tリンパ芽球性リンパ腫の1例

Clinical Features and Prognosis According to Immunophenotypic Subtypes Including the Early T-Cell Precursor Subtype of T-Lymphoblastic Lymphoma in the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 Study.

We reviewed the immunophenotypic subtypes of pediatric T-cell lymphoblastic lymphoma in the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 study. Of the 104 patients, 40 patients each had sufficient data to evaluate the immunophenotypes and early T-cell precursor (ETP) subtype. Pro-T, pre-T, intermediate T, and mature T cells were observed in 1, 9, 21, and 9 cases, respectively. The 3-year event-free survival (EFS) rates of those with pro-T/pre-T, intermediate T, and mature T cells were 80.0±12.6%, 71.4±9.9%, and 88.9±10.5%, respectively (P=0.546). There were 8 and 32 cases of ETP and non-ETP subtypes, with 3-year EFS rates of 75.0±15.3% and 71.9±8.0%, respectively (P=0.828), indicating that the immunophenotypic subtype was not predictive of EFS in this study.

Clinical impact of miR-223 expression in pediatric T-Cell lymphoblastic lymphoma.

Although probability of event-free survival in pediatric lymphoblastic T-cell lymphoma (T-LBL) is about 75%, survival in relapsed patients is very poor, so the identification of new molecular markers is crucial for treatment optimization. Here, we demonstrated that the over-expression of miR-223 promotes tumor T-LBL cell growth, migration and invasion in vitro. We found out that SIK1, an anti-metastatic protein, is a direct target of miR-223 and consequently is significantly reduced in miR-223-overexpressing tumor cells. We measured miR-223 expression levels at diagnosis in tumor biopsies from 67 T-LBL pediatric patients for whom complete clinical and follow up data were available, and we found that high miR-223 expression (above the median value) is associated with worse prognosis (PFS 66% vs 94%, P=0.0036). In addition, the multivariate analysis, conducted taking into account miR-223 expression level and other molecular and clinical characteristics, showed that only high level of miR-223 is an independent factor for worse prognosis. MiR-223 represents a promising marker for treatment stratification in pediatric patients with T-LBL and we provide the first evidence of miR-223 potential role as oncomir by SIK1 repression.

Proposal of a Genetic Classifier for Risk Group Stratification in Pediatric T-Cell Lymphoblastic Lymphoma Reveals Significant Differences to T-Cell Lymphoblastic Leukemia

IntroductionT-cell lymphoblastic lymphoma (T-LBL) represent the second most common subtype of Non-Hodgkin lymphoma (NHL) in children and adolescents. In contrast to other pediatric NHL-subtypes and acute lymphoblastic leukemia (ALL) criteria for the stratification of treatment intensity are lacking in T-LBL. Consequently all patients receive identical treatment intensity resulting in over- and under-treatment of a relevant but not yet characterized subgroup of patients. Recently a genetic classifier for adult T-ALL patients was reported. Whether T-ALL and T-LBL represent one or two diseases remains an ongoing discussion. Whole exome sequencing data of pediatric T-LBL cases now support the hypothesis that T-ALL and T-LBL, despite pathogenic similarities are biologically different. Here we used our large dataset of well defined and uniformly treated pediatric patients with T-LBL to define molecular risk factors of the disease.MethodsAll pediatric T-LBL patients of the NHL-BFM group with sufficient material available were sequenced for abnormalities in the genes: NOTCH1, FBXW7, NRAS, KRAS, PTEN, PIK3R1, PIK3CA using Sanger sequencing of known mutational hotspots and loss of heterozygosity of chromosome 6q using fragment length analyses. Patients were treated uniformly according to NHL-BFM protocols for T-LBL. Clinical data were available from the data base of the NHL-BFM study center. Accompanying molecular research for the trials NHL-BFM 95 and EURO-LB 02, in which these patients were recruited, has been approved by the ethical committees of the Hannover Medical School and Justus-Liebig University Giessen, Germany.ResultsThe observed frequencies of somatic mutations with 95% confidence intervals were: NOTCH1 61% (51-70%), FBXW7 18% (12-27%), PTEN 15% (9-23%) in 114 analyzed patients, N-RAS + K-RAS 10% (5-18%) in 99 analyzed patients, PIK3R1+PIK3CA in 8% (4-15%) in 107 analyzed patients, and LOH6q 12% (8-17%) in 217 analyzed patients. Detailed evaluation of potential associations of distinct mutation status and clinical characteristics revealed a statistically significant association of NOTCH1 mutations (p=0.006) and FBXW7 mutations (p=0.034) with age below 10 years compared to patients with germline status. All other analyses evaluated for each gene separately taking into account age, gender, stage of disease, CNS disease, bone marrow involvement, mediastinal tumor, and general condition at diagnosis did not identify any statistically significant association.Concerning the concurrence or exclusion of the analyzed alterations, NOTCH1 mutations were significantly associated with FBXW7 mutations (p=0.03). LOH6q positive patients presented significantly more often in cases with NOTCH1 wildtype status (p=0.03) and PTEN mutations and FBXW7 mutations turned out to present mutually exclusive (p=0.03).The analyses concerning patients outcome allowed the proposal of an new genetic classifier defining three risk groups:1) Good risk group (GR) comprising 39% (35/91) of patients defined by NOTCH1 mutation and no RAS or PIK3 mutation with a cumulative incidence of relapse of 11+5%.2) Intermediate risk group (IR) with all non-GR and non-HR patients including 46% (42/91) of patients with a cumulative incidence of relapse of 20+6%.3) High-risk group (HR) of 15% (14/91) of patients defined by NOTCH1 wildtype in combination with PTEN mutation and/or LOH6q positivity associated with a cumulative incidence of relapse of 64+14%.Except for an overrepresentation of patients 10 to 15 years of age in the HR arm, none of tested patients’ characteristic parameters of was associated with risk group.ConclusionDetailed analyses of genetic alterations in pediatric T-LBL revealed relevant somatic mutation frequencies for gene loci of the PTEN/PI3K pathway and the RAS pathway. Together with earlier published results on the prognostic relevance of NOTCH1 mutations and chromosome 6q alterations the analyzed cohort of about 100 uniformly treated pediatric T-LBL patients allowed the definition of a genetic classifier for risk group stratification. This proposed classifier requires prospective validation. The here proposed genetic classifier for T-LBL might be worth to be analyzed in pediatric T-ALL. Interestingly our proposed T-LBL classifier includes some aspects in parallel, but overall differed significantly from the earlier published classifier for adult T-ALL. DisclosuresNo relevant conflicts of interest to declare.

The Clinical Features and Prognosis of Early T-Cell Precursor Subtype of Lymphoblastic Lymphoma in the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 Study

Abstract Introduction: Recently, early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) was identified as a subtype of T-cell ALL (T-ALL), with distinctive gene expression and cell marker profiles. Some reports revealed that ETP-ALL was associated with a high risk of remission induction failure and relapse. In precursor T-cell lymphoblastic lymphoma (T-LBL), the clinical features and prognosis of the ETP subtype are not clear yet. In this study, we analyzed the data obtained from patients of advanced stage T-LBL to clarify the prognosis of pediatric T-LBL according to the immunophenotypes, including the ETP subtype of LBL. Patients and methods: From November 2004 to October 2010, 136 children (aged 1–18 years) with newly diagnosed advanced stage LBL (stages III and IV) were eligible for the Japanese Pediatric Leukemia/Lymphoma Study Group ALB-NHL03 study. We analyzed their immunophenotyping data as well as the ETP subtype. The immunophenotype of T-LBL was classified into pro-T, pre-T, intermediate T, and mature T based on the European Group for the Immunological Characterization of Leukemias (EGIL) classification. The definition of ETP subtype LBL was based on a previous report from the Tokyo Children’s Cancer Study Group (Inukai et al, 2011) using a scoring system consisting of the following 11 markers: CD4, CD8, CD13, CD33, CD34, HLA-DR, CD2, CD3, CD4, CD10, and CD56. Both definitions were based on flow cytometric analysis. Results: In this analysis, 104 (76%) patients were diagnosed with T-LBL. Sufficient data to evaluate the EGIL classification was available for 40 out of 104 patients. The remaining patients could not be classified due to incomplete immunophenotypic data. There were 1, 9, 21, and 9 cases of Pro-T, pre-T, intermediate T, and mature T, respectively. The 3-year event-free survival (EFS) of pro-T/pre-T and intermediate T/mature T was 80.0 ± 12.7% and 76.7 ± 7.7%, respectively (P = 0.7586). For evaluating the ETP subtype of LBL, sufficient data, obtained by using the scoring system with 11 markers, was available for 40 patients. Eight (20%) and 32 (80%) patients were classified as having ETP and non-ETP subtype, respectively. Bone marrow involvement for patients with ETP and non-ETP subtype was observed in 7 (88%) and 11 (34%) cases, respectively (P = 0.014). Central nervous system involvement in patients with ETP and non-ETP subtype was observed in 2 (25%) and 0 cases, respectively (P = 0.036). Thus, stage IV classification was more frequently observed in patients with ETP subtype than in patients with non-ETP subtype (P = 0.014). The 3-year EFS of patients with ETP and non-ETP subtype were 75.0 ± 15.3% and 71.9 ± 8.0%, respectively. There was no significant difference in EFS between patients with ETP and non-ETP subtype (P = 0.8281). Conclusion: For 40 out of 104 T-LBL patients, sufficient data was available to evaluate the immunophenotype for EGIL classification and ETP subtype. There was no significant difference in EFS according to the immunophenotypic subtype of T-LBL. In contrast to T-ALL, ETP subtype in LBL was not statistically related to EFS in this analysis. Disclosures No relevant conflicts of interest to declare.

Abstract 3092: PTEN mutations correlate with relapse risk in pediatric T-cell lymphoblastic lymphoma patients: Validation of whole exome sequencing results

Abstract Prognosis of T-cell lymphoblastic lymphoma (T-LBL) in children and adolescents is poor in case of relapse, but pathogenetic knowledge of the disease which may lead to the establishment of prognostic parameters is still extremely limited. Recently, it was reported that molecular aberrations like NOTCH1 mutations or loss of heterozygosity at chromosome 6q (LOH6q) significantly correlate with relapse risk and survival in patients with T-LBL treated according to NHL-BFM protocols. PI3-kinase (PI3K) consists of two subunits (PIK3R1 and PIK3CA); its activity is repressed by the tumor suppressor PTEN. Mutations in PIK3R1, PIK3CA and PTEN leading to increased cell proliferation have been reported for different cancer types. Next generation sequencing (NGS) technologies facilitate in-depth genome-wide insight into different types of cancer. We performed NGS of pediatric T-LBL patients and validated results regarding the PI3K pathway in a large cohort of patients with respect to mutational frequencies and prognostic relevance. We analyzed five pediatric T-LBL cases by whole exome sequencing. A total of 107 cases were available for validation of candidate genes. All patients were treated according to NHL-BFM regimen for LBL. A lymphoma-specific aberration in PIK3R1 was identified via whole exome sequencing and verified by Sanger sequencing. Mutation frequencies in selected exons of PIK3R1, PIK3CA and PTEN were investigated in 107 cases. Five patients (5%) showed mutations in PIK3R1, 7 (7%) in PIK3CA, and 16 (15%) in PTEN. In 22% of the cases (24/107), mutations in at least one of the genes could be detected. These aberrations correlated with inferior probability of event-free survival (pEFS) in the analyzed cohort (pEFS at 5 years 0.80±0.05 vs. 0.61±0.10; p&amp;lt;0.02). This depended on mutations in PTEN, as the effect was more prominent when these aberrations were considered separately (pEFS 0.80±0.04 vs. 0.53±0.13; p&amp;lt;0.005). Although PTEN is reported to be transcriptionally repressed by NOTCH1, NOTCH1 mutations seem to set off the negative effect of PTEN mutations on outcome instead of acting synergistically in T-LBL. The pEFS of patients with mutations in both genes was 0.88±0.12 (N=10), whereas patients with mutations in PTEN, but wild-type NOTCH1 (N=6), displayed a significantly inferior pEFS compared to all other patients (0.17±0.15 vs. 0.80±0.04; p&amp;lt;0.0001). Moreover, in a Cox regression model with LOH6q, NOTCH1, PTEN and an interaction term (NOTCH1 WT/PTEN mutated) only the interaction was significant (p=0.001). Thus, we identified mutations in PTEN as another molecular parameter which is significantly associated with prognosis in pediatric T-LBL patients treated according to NHL-BFM protocols. Validation studies on larger series are needed to evaluate the genetic interplay of these alterations and their impact on pediatric T-LBL pathogenesis. Citation Format: Bettina R. Bonn, Andreas Huge, Marius Rohde, Martin Zimmermann, Reinhard Voss, Wilhelm Woessmann, Lorenz Trümper, Claudia Rossig, Heribert Juergens, Jochen Seggewiss, Birgit Burkhardt. PTEN mutations correlate with relapse risk in pediatric T-cell lymphoblastic lymphoma patients: Validation of whole exome sequencing results. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3092. doi:10.1158/1538-7445.AM2014-3092

Incidence and prognostic relevance of genetic variations in T-cell lymphoblastic lymphoma in childhood and adolescence

AbstractProbability of event-free survival (pEFS) in pediatric T-cell lymphoblastic lymphoma is about 80%, whereas survival in relapsed patients is very poor. No stratification criteria have been established so far. Recently, activating NOTCH1 mutations were reported to be associated with favorable prognosis, and loss of heterozygosity at chromosome 6q (LOH6q) was reported to be associated with increased relapse risk. The current project was intended to evaluate the prognostic effect of these markers. Mutations in hot spots of NOTCH1 and FBXW7 were analyzed in 116 patients. Concerning LOH6q status, 118 patients were investigated, using microsatellite marker analysis, in addition to an earlier reported cohort of 99 available patients. Ninety-two cases were evaluable for both analyses. All patients were treated with T-cell lymphoblastic lymphoma-Berlin-Frankfurt-Münster group (BFM)-type treatment. LOH6q was observed in 12% of patients (25/217) and associated with unfavorable prognosis (pEFS 27% ± 9% vs 86% ± 3%; P < .0001). In 60% (70/116) of the patients, NOTCH1 mutations were detected and associated with favorable prognosis (pEFS 84% ± 5% vs 66% ± 7%; P = .021). Interestingly, NOTCH1 mutations were rarely observed in patients with LOH in 6q16. Both prognostic markers will be used as stratification criteria in coming Non-Hodgkin Lymphoma-BFM trials.

Frequency and clinical relevance of DNA microsatellite alterations of the CDKN2A/B, ATM and p53 gene loci: a comparison between pediatric precursor T-cell lymphoblastic lymphoma and T-cell lymphoblastic leukemia

Although deletions of cell cycle regulatory gene loci have long been reported in various malignancies, little is known regarding their relevance in pediatric T-cell lymphoblastic lymphoma (T-LBL) and T-cell lymphoblastic leukemia (TALL). The current study focused on loss of heterozygosity (LOH) analyses of the CDKN2A/B (chromosome 9p), ATM (chromosome 11q) and p53 (chromosome 17p) gene loci. Frequencies of LOH were compared in 113 pediatric T-LBL and 125 T-ALL who were treated uniformly according to ALL-BFM strategies. Furthermore, LOH findings were correlated with clinical characteristics and tested for their prognostic relevance. LOH at 9p was detected in 47% of T-LBL and 51% of T-ALL, and was associated with male gender in both. In T-ALL, LOH at 9p was associated with favorable initial treatment response. A tendency for favorable event-free-survival was observed in LOH 9p positive T-LBL. The frequency of LOH at chromosomes 11q and 17p was 5% or less for both diseases.

Pediatric T-Cell Lymphoblastic Leukemia and T-Cell Lymphoblastic Lymphoma: Differences in the Common Deleted Region and the Prognostic Impact of Chromosome 6q Deletions.

Background/Objectives: Deletions of chromosome 6q have been reported in a variety of hematological malignancies. Regarding their prognostic impact, however, the data are inconclusive, as most of the published studies included different subtypes, different immunophenotypes and/or differently treated patients (pts).Therefore our analyses focused on 109 pediatric pts with T-cell lymphoblastic-lymphoma (T-LBL) compared with 127 pediatric pts with T-cell lymphoblastic leukemia (T-ALL). Both groups were treated uniformly according to the BFM-ALL-type treatment strategy.Design/Methods: Deletions of chromosome 6q were examined by loss-of-heterozygosity (LOH) analysis of 25 microsatellite-markers located on chromosome 6q14-q24. DNA samples were amplified by PCR, followed by fragment-length analysis on a genetic analyzer.Results: Between 03/95-06/04 a total of 217 pediatric T-LBL pts were registered at the NHL-BFM study center and treated uniformly with ALL-type treatment strategy. 109 T-LBL pts were evaluable for LOH analysis, including 21 out of 27 pts who suffered relapse. In the 109 pts a total of 1,688 markers were analyzed successfully. Patterns of LOH were detectable in 22 pts. Analysis of the putative deleted regions revealed LOH of all informative markers in 5 pts and interstitial deletions in 17 cases. A common deleted region of 13 cases was flanked by markers D6S1682 and D6S1716 at band 6q16. There were no statistically significant differences in LOH-positive versus LOH-negative T-LBL pts with respect to age, sex ratio, stage, BM or CNS involvement. However, detection of LOH at 6q14-24 was associated with poor outcome: Probability of disease-free-survival (DFS) was 91±3% for LOH-negative versus 38±11% for LOH-positive pts (p<0.0001).In comparison, a total of 186 T-ALL pts were consecutively registered in the trial ALL-BFM 2000 between 08/99-06/02. Of these, 127 pts were evaluable for LOH analysis, including 22 out of 27 pts with relapse. In the 127 pts a total of 3,109 markers were analyzed successfully. Patterns of LOH were detected in 16 pts with proximal interstitial deletions in 15 out of the 16 cases. The 4.3 Mb common deleted region was flanked by markers D6S1627 and D6S1644. There were no significant differences between LOH-positive versus LOH-negative pts neither in clinical characteristics nor in treatment response or outcome.Conclusions: The pattern of 6q-deletions as well as the prognostic impact differ between pediatric T-LBL and T-ALL. LOH at 6q is detectable in 20% of pediatric T-LBL compared with 13% of pediatric T-ALL. In T-ALL the common deleted region is localized in chromosomal band 6q14. LOH is not associated with clinical parameters or outcome. In T-LBL the most frequently deleted marker is localized in band 6q16 and detectable LOH is associated with poor outcome. A prospective analysis of a larger series of pts is necessary to confirm the prognostic value of 6q deletions in T-LBL.