Relevance of flow cytometry categorization and end-of-induction measurable residual disease assessment in pediatric and adult T-lymphoblastic leukemia patients
Karthik Bommannan1, Jhansi Rani Arumugam1, Venkatraman Radhakrishnan2, Jayachandran Perumal Kalaiyarasi2, Parathan Karunakaran2, Nikita Mehra2, Tenali Gnana Sagar2, Shirley Sundersingh1
1 Departments of Oncopathology and 2Medical Oncology, Cancer Institute (W.I.A.), Adyar, India
Correspondence to: Karthik Bommannan
Department of Oncopathology, Cancer Institute (W.I.A.) Adyar, Chennai, India 600020
E-mail: bkkb87@gmail.com
Published online: July 27, 2022.
© The Korean Journal of Hematology. All rights reserved.

Abstract
Background: T-lymphoblastic leukemia (T-ALL) patients expressing myeloid/stem cell antigens are classified as early T-cell precursor lymphoblastic leukemia (ETP-ALL) or near-ETP-ALL.
Methods: Clinico-laboratory profiles, flow cytometry end-of-induction measurable residual disease (EOI-MRD), and survival of treatment naïve T-ALL patients were analyzed according to their immunophenotypic subtypes.
Results: Among 81 consecutive T-ALL patients diagnosed, 21% (N=17) were ETP-ALL and 19% (N=15) were near-ETP-ALL. EOI-MRD was detectable in 39% of the 59 samples tested (31.6% of pediatric samples and 52.4% of adult samples). The frequency of EOI-MRD positivity was significantly higher among ETP-ALL (75%, P=0.001) and near-ETP-ALL (71%, P=0.009) patients compared to that in conventional-T-ALL (con-T-ALL) patients (22.5%). CD8 (P=0.046) and CD38 (P=0.046) expressions were significantly upregulated in the EOI blasts of con-T-ALL and ETP-ALL samples, respectively. The 2-year rates of overall (OS), relapse-free (RFS), and event-free survival (EFS) among the T-ALL patients (pediatric vs. adult) was 79.5% vs. 39.8% (P<0.001), 84.3% vs. 60.4% (P=0.026), and 80.3% vs. 38% (P<0.001), respectively. Univariate analysis revealed that 2-year EFS and RFS of pediatric T-ALL patients was independent of T-ALL subtype and was influenced only by EOI-MRD status. However, 2-year OS, RFS, and EFS among adult T-ALL patients were EOIMRD independent and influenced only by the near-ETP-ALL phenotype.
Conclusion: Two-year survival among pediatric and adult T-ALL patients is attributed to EOI-MRD status and near-ETP-ALL phenotype, respectively.
Keywords: Measurable residual disease, Flow cytometry, T-lineage acute lymphoblastic leukemia, ETP-ALL, Near-ETP-ALL


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