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212 The Clinical Outcomes and Genomic Landscapes of Acute Lymphoblastic Leukemia Patients with E2A-PBX1: A 10-Year Retrospective StudyClinically Relevant Abstract

Program: Oral and Poster Abstracts
Type: Oral
Session: 612. Acute Lymphoblastic Leukemias: Clinical and Epidemiological: Clinical, genetic and societal risk factors impacting ALL outcomes
Hematology Disease Topics & Pathways:
Lymphoid Leukemias, ALL, Diseases, Lymphoid Malignancies
Saturday, December 11, 2021: 2:15 PM

Biqi Zhou1,2*, Xinran Chu, M.D.3*, Hong Tian, M.D.1*, Tianhui Liu, PhD1,2*, Hong Liu, M.D.1*, Wei Gao, M.D.3*, Suning Chen2,4*, Shaoyan Hu, MD, PhD3, Depei Wu, MD, PhD2,5 and Yang Xu, MD, PhD1,2*

1Jiangsu Institute of Hematology, National Clinical Research Center for Hematologic Diseases, The First Affiliated Hospital of Soochow University, Suzhou, China
2Institute of Blood and Marrow Transplantation, Collaborative Innovation Center of Hematology, Soochow University, Suzhou, China
3Department of Hematology, Children's Hospital of Soochow University, Suzhou, China
4The First Affiliated Hospital of Soochow University, Suzhou, China
5Jiangsu Institute of Hematology, National Clinical Research Center for Hematologic Diseases, NHC Key Laboratory of Thrombosis and Hemostasis, The First Affiliated Hospital of Soochow University, Suzhou, China

Introduction

Patients with E2A-PBX1 fusion are expected to have an aggressive disease course. Because of the rarity of this genotype (nearly 5% of pediatric and 3% of adult B-cell acute lymphoblastic leukemia (B-ALL) cases), a consensus on the clinical and prognostic characteristics of adult E2A-PBX1-positive B-ALL patients, especially in adult patients, has not yet been reached.

Patients and Methods

We retrospectively summarized our clinical findings from 137 B-ALL patients diagnosed with E2A-PBX at our centers from 2009 to 2019, including 56 adolescents/adults (≥15 years old) and 81 children (<15 years old). Genomic investigated analysis was performed on sufficient bone marrow at diagnosis, relapse and remission as well as matched hair follicle cells using somatic copy number variation detection (n=25), whole-exome sequencing (n=29), the next-generation sequencing pane (tumor only, n=14) and RNA sequencing (n=22).

Results

The proportions of E2A-PBX1-positive B-ALL in our centers were 5.3% (81/1526) in children, 4.6% (43/925) in AYA and 2.1% (15/713) in older adults. The complete remission rate among all E2A-PBX1-positive B-ALL patients in this study was 94.9% (129/136) after one course of induction chemotherapy. The 5-year overall survival (OS) and disease-free survival (DFS) rates of the whole cohort were 68.6% and 61.0%, respectively.

Allo-HSCT at CR1 in adolescents/adults could dramatically improve the 5-year prognoses (OS: 80.8% vs. 25.7%, P<0.001; DFS: 73.3% vs. 15.5%, P<0.001; cumulative incidence of relapse (CIR): 20.0% vs. 80.5%, P<0.001) (Figure 1A). Haploidentical-HSCT decreased the CIR compared with HLA-matched-HSCT in adolescents/adults (12.5% vs 58.3%, P=0.017) (Figure 1B).

A total of 12 patients received CD19-targeted CAR-T cell therapy for disease progression (Figure 1C), and 91.7% (11/12) of patients achieved remission. Two patients died of relapse, and 3 patients died of complications (One died of grade 4 CRS, one died of cerebral hemorrhage after transfusion, and the other one died of infection after 14 months). Three patients received CAR-T bridging to allo-HSCT, and all of them remained in remission within the follow-up period.

Univariate and multivariate analysis showed that t(1;19)(q23;p13) only (OS: P=0.020, HR=0.387, 95% CI: 0.174-0.862; DFS: P=0.004, HR= 0.375, 95% CI: 0.193-0.729; CIR: P=0.009, HR= 0.400, 95% CI: 0.200-0.799), Age (DFS: P=0.037, HR=1.009, 95% CI: 1.001-1.018; CIR: P=0.005, HR=1.025, 95% CI: 1.008-1.044) and the level of minimal residual disease (MRD) after induction chemotherapy (OS: P=0.020, HR=2.971, 95% CI: 1.185-7.452; DFS: P=0.002, HR= 3.218, 95% CI: 1.510-6.861; CIR: P=0.006, HR= 3.190, 95% CI: 1.406-7.246) were independent risk factors in E2A-PBX1-positive B-ALL (Figure 1D).

In the diagnosis samples, mutations in PBX1, PAX5, CTCF and SETD2, amplification of AKT3, and deletion of CDKN2A/B were common in the total cohort, while transcriptome differences were found in the cell cycle, NGF signaling pathway and transcriptional regulation by TP53 between adolescents/adults and children (Figure 2A,B). More DNA repair gene mutations were detected in the relapse samples (7.9% vs. 57.1%, P<0.001). The median number of subclones in E2A-PBX1-positive B-ALL at diagnosis was 2 (range 1-4). Patients with multiple subclones at diagnosis tended to have unfavorable 3-year prognoses (DFS: P=0.010; CIR: P=0.021). Leukemia clones with DNA repair gene mutations showed aggressive and treatment-refractory phenotypes in this subtype of ALL (Figure 2C).

Conclusions

Our study indicated that age, the level of MRD and DNA repair gene mutations were associated with E2A-PBX1-positive B-ALL outcomes. Allo-HSCT, especially haploidentical-HSCT, could improve the prognosis of adolescent/adult patients.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH