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2844 Dissecting the Role of Acquired Regions of Homozygosity Detected By Microarray Along the Genome of a Large Cohort of Adult Patients with B-Cell Precursor Acute Lymphoblastic Leukemia

Program: Oral and Poster Abstracts
Session: 614. Acute Lymphoblastic Leukemias: Biomarkers, Molecular Markers, and Minimal Residual Disease in Diagnosis and Prognosis: Poster II
Hematology Disease Topics & Pathways:
Lymphoid Leukemias, ALL, Research, Genomics, Clinical Research, Diseases, Lymphoid Malignancies, Biological Processes, Technology and Procedures, Omics technologies
Sunday, December 8, 2024, 6:00 PM-8:00 PM

Gianfranco Lapietra1*, Jordi Ribera2*, Mireia Morgades2*, Neus Ruiz Xiville, PhD2*, Anna Torrent, MD3*, Mar Mallo4*, Jesus Maria Hernandez Rivas, MD5, Alberto Hernández Sánchez, MD6*, Alberto Orfao, MD, PhD7*, Isabel Granada, MD8*, Jose Tomas Navarro, MD, PhD9*, Ilaria Del Giudice10*, Maurizio Martelli, MD11*, Sabina Chiaretti, MD, PhD12 and Josep-Maria Ribera, MD, PhD13,14

1Josep Carreras Leukemia Research Institute, Badalona (ES)/ Hematology, Department of Translational and Precision Medicine, Sapienza, University of Rome (IT), Badalona, Spain
2ICO-Hospital Germans Trias i Pujol, Institut de Recerca contra la Leucèmia Josep Carreras (IJC), Universitat Autònoma de Barcelona, Badalona, Spain
3Hematology department, Institut Català D'oncologia-Hospital Germans Trias I Pujol. Josep Carrera, Badalona, Spain
4Myelodysplastic Syndromes Research Group, Josep Carreras Leukaemia Research Institute, ICO-Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Barcelona, Spain
5University of Salamanca, IBSAL, IBMCC, CSIC, Cancer Research Center, Salamanca, Spain
6Translational and Clinical Research Program, Cancer Research Center (IBMCC, CSIC – University of Salamanca); Cytometry Service, NUCLEUS; Department of Medicine, University of Salamanca (Universidad de Salamanca), Salamanca, Spain. IBSAL (Salamanca, Spain), Salamanca, Spain
7Cancer Research Center (IBMCC-CSIC/USAL-IBSAL), Cytometry Service (NUCLEUS) and Department of Medicine, University of Salamanca, Salamanca, Spain
8Haematology Department, Hospital Germans Trias i Pujol-Catalan Institute of Oncology., Badalona, Spain
9Hematology Department, ICO Badalona, Germans Trias i Pujol University Hospital. Universitat Autònoma de Barcelona. Josep Carreras Leukemia Research Institute, Badalona, Spain
10Hematology, Department of Translational and Precision Medicine, Sapienza University, Roma, Italy
11Hematology, Department of Translational and Precision Medicine, Sapienza University of Rome, Rome, Italy
12Department of Translational and Precision Medicine, Division of Hematology, Sapienza University, Rome, Italy
13Ico-Hospital Universitari Germans Trias Y Pujol, Badalona, Barcelona, ESP
14Josep Carreras Leukemia Research Institute, Badalona, Barcelona, Spain., Badalona, Spain

INTRODUCTION

Acquired regions of homozygosity (aROHs) detected along the human genome are due to mitotic recombination between homologous chromosomes. This mechanism may contribute to the growth of a neoplastic clone if the involved region embraces tumor suppressor or onco-genes harbouring a mutation, with subsequent loss of the wild-type allele and duplication of the aberrant one. Cytogenetic diagnostic tools based on allelic load assay have allowed identification of aROHs also in B-cell acute lymphoblastic leukemia (B-ALL). However, real-life data about contribution of these aberrations to leukemogenesis are scarce and controversial. Therefore, we investigated aROHs detected in a large and uniform longitudinal cohort of adult B-ALL patients (pts).

METHODS

The study was carried out at the Cytogenetic Unit of Catalan Institute of Oncology-Josep Carreras Leukemia Research Institute (Badalona, ES). Pts enrolled in clinical trial NCT04179929 (LAL-19) with available single nucleotide polymorphisms (SNP)-array analysis performed at baseline for genetic risk-stratification as per protocol were considered evaluable. For each patient, DNA extracted from infiltrated bone marrow (BM) and amplified by PCR was hybridized to Cytoscan 750 K array (Affymetrix, Santa Clara, CA, US). Hybridization to each probe was assessed using a GeneChip Scanner (Affymetrix) and results scored using CHAS v4.5 software (Affymetrix). For the aim of the study, we first selected ROHs with size≥3 Mb and mapping in regions covered with≥20 consecutive probes. In order to identify only acquired non-polymorphic forms, we excluded ROHs overlapping ≥50% of their length with regions included in public databases of healthy controls and with variant of allele frequency (VAF)>BM infiltration. Finally, eligible calls were cross-referenced with pts' biological and clinical data for statistical analysis.

RESULTS

From December 2019 to March 2024, 371 pts were included in LAL-19 trial. Two hundred and seventy seven cases (75%) were eligible for our study. Median age was 40 years (range 18-60). The male/female ratio was 1:1. Overall, 332 aROHs were detected in 156 pts (56%). The median number of aROHs per pt was one (range 1-9); the median size was 6.7 Mb (range 3-27.5). Ninety-four % of aROHs were segmental. aROHs were distributed across the whole genome, 5q31.1 and 7q11.23 being the most frequently involved regions, without affecting any gene clearly involved in the leukemogenesis. No difference was observed between pts with and without aROHs in terms of age, sex and clinical features at the onset. However, the presence of aROHs was associated with the absence of hypodiploidy (<44 chromosomes) and absence of mutations in the survival regulatory pathways detected by NGS standard panel (p=0.029 and p=0.043, respectively). Based on follow-up (FU) data, survival analysis was possible in 192/277 pts (69%). After a median FU of one year, the presence of aROHs had no impact on either overall survival (OS) (p=0.594) or cumulative incidence of relapse (CIR) (p=0.893). Within the population with aROHs, no difference emerged in terms of OS and CIR stratifying by number (1 versus ˃1) and size of lesions (<20 Mb versus >20 Mb, being 20 Mb the most employed cut-off in literature).

CONCLUSIONS

Our study confirms recurrence of non-polymorphic aROHs along the genome of adult B-ALL pts, without affecting key-genes for leukemogenesis. These aberrations do not impact the prognosis. On the contrary, a protective role for the genome could be hypothesized, due to their association with a low rate of mutation and with preserved diploidy.

Disclosures: Torrent: Amgen: Honoraria; Pfizer: Honoraria; Kite: Honoraria; Incyte: Honoraria. Hernandez Rivas: Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GlaxoSmithKline: Consultancy, Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Del Giudice: Takeda: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jansenn: Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Other: educational and editorial projects; Roche: Other: educational and editorial projects. Chiaretti: Abbvie: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees. Ribera: Incyte: Consultancy; Pfizer: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Amgen: Research Funding.

*signifies non-member of ASH