Ah Moy Tan

Minimal Residual Disease–Guided Treatment Deintensification for Children With Acute Lymphoblastic Leukemia: Results From the Malaysia-Singapore Acute Lymphoblastic Leukemia 2003 Study

PURPOSEnTo improve treatment outcome for childhood acute lymphoblastic leukemia (ALL), we designed the Malaysia-Singapore ALL 2003 study with treatment stratification based on presenting clinical and genetic features and minimal residual disease (MRD) levels measured by polymerase chain reaction targeting a single antigen-receptor gene rearrangement.nnnPATIENTS AND METHODSnFive hundred fifty-six patients received risk-adapted therapy with a modified Berlin-Frankfurt-Münster-ALL treatment. High-risk ALL was defined by MRD ≥ 1 × 10(-3) at week 12 and/or poor prednisolone response, BCR-ABL1, MLL gene rearrangements, hypodiploid less than 45 chromosomes, or induction failure; standard-risk ALL was defined by MRD ≤ 1 × 10(-4) at weeks 5 and 12 and no extramedullary involvement or high-risk features. Intermediate-risk ALL included all remaining patients.nnnRESULTSnPatients who lacked high-risk presenting features (85.7%) received remission induction therapy with dexamethasone, vincristine, and asparaginase, without anthracyclines. Six-year event-free survival (EFS) was 80.6% ± 3.5%; overall survival was 88.4% ± 3.1%. Standard-risk patients (n = 172; 31%) received significantly deintensified subsequent therapy without compromising EFS (93.2% ± 4.1%). High-risk patients (n = 101; 18%) had the worst EFS (51.8% ± 10%); EFS was 83.6% ± 4.9% in intermediate-risk patients (n = 283; 51%).nnnCONCLUSIONnOur results demonstrate significant progress over previous trials in the region. Three-drug remission-induction therapy combined with MRD-based risk stratification to identify poor responders is an effective strategy for childhood ALL.

Allogeneic stem cell transplantation for children with acquired severe aplastic anaemia: a retrospective study by the Viva-Asia Blood and Marrow Transplantation Group

We retrospectively analysed the outcomes of 127 children with acquired severe aplastic anaemia (SAA) who had received haematopoietic stem cell transplantation (HSCT) between 2000 and 2011 in one of the 10 Asia Pacific institutions. Fifty‐three were matched sibling donor (MSD) and 74 were alternative donor (AD), including 22 matched unrelated donor, 32 mismatched unrelated donor and 20 mismatched related donor. With a median follow up 45·5 months (13–139) and when compared to the MSD group, AD recipients had more grade II‐IV acute graft‐versus‐host disease (aGVHD; 14·3% vs. 32·8%, P = 0·029), but similar grade III‐IV aGVHD (10·2% vs. 12·5%, P = 0·774), graft failure (GF) (15·1% vs. 15·5%, P = 0·658) and 5‐year overall survival (90·6% vs. 83·7%, P = 0·251). As a source of stem cell, peripheral blood stem cells (PBSC) resulted in less GF (18% vs. 9·1% P = 0·013), similar grade II‐IV aGVHD (28·1% vs. 17·4%, P = 0·258), chronic GVHD (25·8% vs. 29·3%, P = 0·822) and similar outcomes (89·7% vs. 82·4%, P =0 ·665) when compared to bone marrow (BM). In univariate analysis, GF (P < 0·001) and grade II‐IV aGVHD (P = 0·009) were predictors of poor survival. In multivariate analysis, only GF was associated with poor survival (P = 0·012). The outcome of AD and PBSC HSCT were comparable to that of MSD and BM HSCT in the Asia Pacific region.

Whole-transcriptome sequencing identifies a distinct subtype of acute lymphoblastic leukemia with predominant genomic abnormalities of EP300 and CREBBP

Chromosomal translocations are a genomic hallmark of many hematologic malignancies. Often as initiating events, these structural abnormalities result in fusion proteins involving transcription factors important for hematopoietic differentiation and/or signaling molecules regulating cell proliferation and cell cycle. In contrast, epigenetic regulator genes are more frequently targeted by somatic sequence mutations, possibly as secondary events to further potentiate leukemogenesis. Through comprehensive whole-transcriptome sequencing of 231 children with acute lymphoblastic leukemia (ALL), we identified 58 putative functional and predominant fusion genes in 54.1% of patients (n = 125), 31 of which have not been reported previously. In particular, we described a distinct ALL subtype with a characteristic gene expression signature predominantly driven by chromosomal rearrangements of the ZNF384 gene with histone acetyltransferases EP300 and CREBBP ZNF384-rearranged ALL showed significant up-regulation of CLCF1 and BTLA expression, and ZNF384 fusion proteins consistently showed higher activity to promote transcription of these target genes relative to wild-type ZNF384 in vitro. Ectopic expression of EP300-ZNF384 and CREBBP-ZNF384 fusion altered differentiation of mouse hematopoietic stem and progenitor cells and also potentiated oncogenic transformation in vitro. EP300- and CREBBP-ZNF384 fusions resulted in loss of histone lysine acetyltransferase activity in a dominant-negative fashion, with concomitant global reduction of histone acetylation and increased sensitivity of leukemia cells to histone deacetylase inhibitors. In conclusion, our results indicate that gene fusion is a common class of genomic abnormalities in childhood ALL and that recurrent translocations involving EP300 and CREBBP may cause epigenetic deregulation with potential for therapeutic targeting.

Host genetic variants of ABCB1 and IL15 influence treatment outcome in paediatric acute lymphoblastic leukaemia

Background:Host germline variations and their potential prognostic importance is an emerging area of interest in paediatric ALL.Methods:We investigated the associations between 20 germline variations and various clinical end points in 463 children with ALL.Results:After adjusting for known prognostic factors, variants in two genes were found to be independently associated with poorer EFS: ABCB1 T/T at either 2677 (rs2032582) or 3435 (rs1045642) position (P=0.003) and IL15 67276493G/G (rs17015014; P=0.022). These variants showed a strong additive effect affecting outcome (P<0.001), whereby patients with both risk genotypes had the worst EFS (P=0.001), even after adjusting for MRD levels at the end of remission induction. The adverse effect of ABCB1 T/T genotypes was most pronounced in patients with favourable cytogenetics (P=0.011) while the IL15 67276493G/G genotype mainly affected patients without common chromosomal abnormalities (P=0.022). In both cytogenetic subgroups, increasing number of such risk genotypes still predicted worsening outcome (P<0.001 and=0.009, respectively).Conclusion:These results point to the prognostic importance of host genetic variants, although the specific mechanisms remain unclarified. Inclusion of ABCB1 and IL15 variants may help improve risk assignment strategies in paediatric ALL.

Intensifying Treatment of Childhood B-Lymphoblastic Leukemia With IKZF1 Deletion Reduces Relapse and Improves Overall Survival: Results of Malaysia-Singapore ALL 2010 Study

Purpose Although IKZF1 deletion ( IKZF1del) confers a higher risk of relapse in childhood B-cell acute lymphoblastic leukemia (B-ALL), it is uncertain whether treatment intensification will reverse this risk and improve outcomes. The Malaysia-Singapore ALL 2010 study (MS2010) prospectively upgraded the risk assignment of patients with IKZF1del to the next highest level and added imatinib to the treatment of all patients with BCR- ABL1 fusion. Patients and Methods In total, 823 patients with B-ALL treated in the Malyasia-Singapore ALL 2003 study (MS2003; n = 507) and MS2010 (n = 316) were screened for IKZF1del using the multiplex ligation-dependent probe amplification assay. The impact of IKZF1del on the 5-year cumulative incidence of relapse (CIR) was compared between the two studies. Results Patient characteristics were similar in both cohorts, including IKZF1del frequencies (59 of 410 [14.4%] v 50 of 275 [18.2%]; P = .2). In MS2003, where IKZF1del was not used in risk assignment, IKZF1del conferred a significantly higher 5-year CIR (30.4% v 8.1%; P = 8.7 × 10-7), particularly in the intermediate-risk group who lacked high-risk features (25.0% v 7.5%; P = .01). For patients with BCR-ABL1-negative disease, IKZF1del conferred a higher 5-year CIR (20.5% v 8.0%; P = .01). In MS2010, the 5-year CIR of patients with IKZF1del significantly decreased to 13.5% ( P = .05) and no longer showed a significant difference in patients with BCR-ABL1-negative disease (11.4% v 4.4%; P = .09). The 5-year overall survival for patients with IKZF1del improved from 69.6% in MS2003 to 91.6% in MS2010 ( P = .007). Conclusion Intensifying therapy for childhood B-ALL with IKZF1del significantly reduced the risk of relapse and improved overall survival. Incorporating IKZF1del screening significantly improved treatment outcomes in contemporary ALL therapy.

Effective Response Metric: a novel tool to predict relapse in childhood acute lymphoblastic leukaemia using time-series gene expression profiling

Accurate risk assignment in childhood acute lymphoblastic leukaemia is essential to avoid under‐ or over‐treatment. We hypothesized that time‐series gene expression profiles (GEPs) of bone marrow samples during remission‐induction therapy can measure the response and be used for relapse prediction. We computed the time‐series changes from diagnosis to Day 8 of remission‐induction, termed Effective Response Metric (ERM‐D8) and tested its ability to predict relapse against contemporary risk assignment methods, including National Cancer Institutes (NCI) criteria, genetics and minimal residual disease (MRD). ERM‐D8 was trained on a set of 131 patients and validated on an independent set of 79 patients. In the independent blinded test set, unfavourable ERM‐D8 patients had >3‐fold increased risk of relapse compared to favourable ERM‐D8 (5‐year cumulative incidence of relapse 38·1% vs. 10·6%; P = 2·5 × 10−3). ERM‐D8 remained predictive of relapse [P = 0·05; Hazard ratio 4·09, 95% confidence interval (CI) 1·03–16·23] after adjusting for NCI criteria, genetics, Day 8 peripheral response and Day 33 MRD. ERM‐D8 improved risk stratification in favourable genetics subgroups (P = 0·01) and Day 33 MRD positive patients (P = 1·7 × 10−3). We conclude that our novel metric – ERM‐D8 – based on time‐series GEP after 8 days of remission‐induction therapy can independently predict relapse even after adjusting for NCI risk, genetics, Day 8 peripheral blood response and MRD.