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4208 Philadelphia-like B-Cell Acute Lymphoblastic Leukemia in a Largely Hispanic Population: Disease Features and Outcomes in the Era of Immunotherapy a Single Institutional Study

Program: Oral and Poster Abstracts
Session: 612. Acute Lymphoblastic Leukemias: Clinical and Epidemiological: Poster III
Hematology Disease Topics & Pathways:
ALL, Research, Lymphoid Leukemias, Clinical Research, health disparities research, Diseases, real-world evidence, Lymphoid Malignancies
Monday, December 11, 2023, 6:00 PM-8:00 PM

Karam Ashouri, MD1, Brian Hom1*, Yekta Rahimi, MD2*, Karen Resnick, MD1*, Vinay Nittur, MD1*, Jennifer Hwang, MD1*, Blake Adnani, MD2*, Mollee Chu, MD1*, Anush Aram Ginosyan, MD1*, Robert Ireland, MD1*, Eljie Isaak Bragasin1*, Shirley Ye, MD2, Lakshmi Savitala-Damerla3*, Kimberly Schiff3*, Preet M. Chaudhary, MD, PhD3, Imran Siddiqi, MD, PhD3*, Abdullah Ladha, MD3*, Amir Ali, PharmD, BCOP3, Karrune Woan, MD, PhD3*, Eric Tam, MD3* and George Yaghmour, MD3

1Keck School of Medicine, University of Southern California, Los Angeles, CA
2Keck School of Medicine, University of Southern California, Los Angeles
3Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA


Philadelphia (Ph)-like B-cell acute lymphoblastic leukemia (ALL) is a high-risk subgroup of B- cell ALL with distinct genotypes, unified by a gene expression profile similar to Ph-positive ALL but lacking the BCR: ABL1 fusion. Previous studies have noted the increased prevalence of Ph-like B-cell ALL in Hispanic patients. Our study evaluates Ph-like B- cell ALL clinical/genomic features and outcomes in a predominantly Hispanic population.

Methods: This is a retrospective chart review of ALL patients that underwent treatment for B-cell ALL at Norris Comprehensive Cancer Center (NCCC) between 2011 and 2023. Identification of fusions associated with Ph-like B-cell ALL was performed using cumulative results from RNA-seq, conventional cytogenetics, and fluorescence in situ hybridization (FISH) with reflex gene fusion transcript analysis. Additionally, we used the Anchored Multiplex PCR™-based multi-gene NGS assay designed to detect known and novel fusions and elevated gene expression levels using a proprietary algorithm in ALL.

Cumulative incidence of relapse (CIR) was evaluated using competing risk regression (Fine-Gray method), with death as a competing outcome. Overall survival (OS) and event-free survival (EFS) were analyzed using Cox proportional hazards model. Events of interest for EFS were relapse, treatment failure, and death. Ph-negative B-cell ALL patients were set as the reference for survival analysis.

Results: 253 patients were included with a median age at diagnosis of 42 years (range: 18-80). ALL subtypes included 64(25.3%) Ph-like, 77(30.4%) Ph-positive, and 112(44.3%) Ph-negative. Most were Hispanic (N = 186, 73.5%), and the median follow-up time was 27 months. The 3-year OS, EFS, and CIR were 81.3% (95% CI 75.7-87.4%), 49.1% (95% CI 42.7-56.5%), and 39.9% (95% CI 33.0-46.7%).

CRLF2 related mutations constituted 44(68.8%) of Ph-like patients, with 9(14.0%) CRLF2-P2RY8, 24(37.5%) CRLF2-IGH, and 11(17.2%) CRLF2-other gene rearrangements. 19 Ph-like patients had non-CRLF2 mutations consisting of 13(20.3%) IGH, 3(4.7%) ABL1/2, 3(4.7%) JAK2, and 1(1.6%) EPOR rearrangements.

Compared to Ph-negative, Ph-like patients were more likely to have a refractory disease (20.6% vs. 6.2% P=0.006) and require Blinatumomab (67.2% vs. 39.3% P<0.001), with a non-significant trend towards lower rates of CR (84.1% vs 90.9% P=0.21). Ph-like patients had significantly worse EFS (HR = 1.63; 95% CI 1.09-2.45; P=0.018), but similar OS (HR = 0.88; 95% CI 0.39-1.99; P=0.75) and CIR (HR = 1.06; 95% CI 0.65-1.70; P = 0.83). Ph-positive patients displayed improved EFS relative to Ph-negative (HR = 0.56; 95% CI 0.35-0.91; P = 0.018), similar OS (HR = 0.73; 95% CI 0.35-1.50; P = 0.39), and a trend towards improved CIR (HR = 0.67; 95% CI 0.40-1.10; P=0.11). When controlling for age, sex, and treatment type, EFS was worse in Ph-like (HR = 1.57; 95% CI 1.03-2.41; P = 0.037) and improved in Ph-positive (HR = 0.56; 95% CI 0.33-0.93; P = 0.026).

Our incidences of CRLF2 mutations in Ph-like patients aged>40 compared to age ≤40 was (73.3% vs 64.7%, P=0.591). On subgroup analysis of Ph-like patients, univariate regression revealed CRLF2-related Ph-like patients had a worse CIR (HR = 5.68; 95% CI 1.91-16.9; P = 0.002) but similar OS(P=0.99) and EFS(P=0.18). PAX5 expression was also a predictor of poor OS (HR = 8.89; 95% CI 1.06-74.7; P = 0.044) and EFS (HR = 2.51; 95% CI 1.09-5.77; P = 0.031), with a trend towards increased CIR (HR = 2.30; 95% CI 0.92 -5.78; P = 0.075). Compared to non-CRLF2 mutations, CRLF2-Ph-like had worse CIR (HR = 5.68; 95% CI 1.91 -16.9; P = 0.002). Relative to Ph-like patients who achieved MRD negativity during induction, patients who remained MRD positive had worse CIR(HR = 2.92; 95% CI 1.23 -6.94; P = 0.015) and EFS (HR = 4.32; 95% CI 1.890-9.84; P < 0.001). However, after controlling for Blinatumomab administration, the effect diminished (CIR: P=0.73, EFS P=0.28). There were no differences in EFS(P=0.34), CIR(P=0.69), and OS(P=0.36) between Ph-like patients who were transplanted vs not.


Ph-like B- Cell ALL represents a high-risk disease subtype of adult B-ALL, with poor EFS and frequent treatment failure. CRLF2 translocation confers worse CIR and EFS within Ph-like patients and requires novel treatment approaches.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH