BackgroundMeasurable residual disease (MRD) assessment using multicolor flow cytometry (MFC) has become the center point of pediatric B‐cell precursor acute lymphoblastic leukemia (BCP‐ALL) risk stratification and therapeutic management. The addition of new markers can improve the accuracy and applicability of MFC‐based MRD assay further. Herein, we evaluated the utility of a new marker, CD304/neuropilin‐1, in the assessment of MFC‐based MRD.MethodsExpression patterns of CD304 were studied in leukemic blasts from BCP‐ALL patients and in normal precursor B cells (NPBC) from uninvolved non‐BCP‐ALL bone marrow samples using 10‐color MFC. MRD was monitored at end‐of‐induction (EOI; Days 35–40) and end‐of‐consolidation (Day 78–80) time points.ResultsWe studied CD304 expression in 300 pediatric BCP‐ALL patients and found it positive in BCP‐ALL blasts in 41.7% of diagnostic samples. It was significantly associated with ETV6‐RUNX1 (p < .001) as well as BCR‐ABL1 (p = .019) and inversely associated with TCF3‐PBX1 fusion gene (p = .0012). It was found clearly negative in NPBC. EOI‐MRD was detectable in 152/300 (50.7%; ≥0.01% in 35.33% and <0.01% in 15.33%) samples, in which CD304 was positive in 72/152 (47.4%) diagnostic and 63/152 (41.4%) MRD samples. It was positive in 45.7% (21/46) of low‐level (<0.01%) MRD samples. In comparison with diagnostic samples, its expression was retained in 68.06% (49/72), lost in 31.94% (23/72), and gained in 14/80 (17.5%) of EOI‐MRD samples.ConclusionsCD304 is commonly expressed in leukemic blasts of BCP‐ALL. It is very useful in distinguishing residual disease from hematogones and is a fairly dependable marker. Hence, it is a valuable addition for enhancing the sensitivity and applicability of MFC‐based MRD assay in BCP‐ALL.

Background: Measurable/minimal residual disease (MRD) status is suggested as a powerful indicator of clinical-outcome in T-cell lymphoblastic leukemia/lymphoma (T-ALL). Contrary to B-cell ALL, reports on TALL MRD are limited and mostly based on molecular methods, mainly from developed countries. Multicolor flow cytometry (MFC)-based TALL studies are very few. Clinically relevant cutoff levels and ideal time-point for MRD assessment are still inconclusive. In view of lack of TALL MRD data from the developing world, we evaluated the prognostic value of MFC-based post-induction (PI)-MRD assessment in TALL in the context of standard practice. Methods: We included 256 childhood-TALL patients (age < 15 years) treated with a modified-MCP841 protocol, which uses high-dose cytarabine during consolidation, as a part of standard hospital practice. MRD was studied using 10-color 11-antibody MFC with any level of detectable disease being considered positive. Post-induction (PI)-MRD was available in all patients, and post-consolidation (PC) MRD was available mostly in PI-MRD-positive patients (n = 88). Results: Three years cumulative-incidence-of-relapse (3years-CIR) in PI-MRD-positive patients was inferior to negative patients (46.3% vs. 18.4%). The median relapse-free-survival (RFS), event-free-survival (EFS) and overall-survival (OS) with hazard ratio (HR) of PI-MRD-positive patients were 21.4 months vs not reached (p < 0.0001, HR-4.7), 21.6 months vs. not-reached (p = 0.0003, HR-2.01) and 37.3 months vs. not reached (p = 0.026, HR-1.64) respectively. RFS, EFS and OS of patients with PI-MRD<0.01% (n = 17) were as inferior as PI-MRD ≥ 0.01% in comparison Tembhare et al. Post-induction MRD & WBC Count in TALL with MRD-negative patients with HR of 4.7 (p < 0.0001), 2.45 (p = 0.0003), and 2.5 (p = 0.029), respectively. Three-years-CIR of patients with hyperleukocytosis (≥100 × 109/L) was also higher (50.5 vs. 27.6%) with inferior RFS, EFS, and OS. Among PI-MRDpositive patients, 3years-CIR, RFS, EFS, and OS of PC-MRD-positive were also inferior to that of negative patients. On multivariate analysis any-level detectable PI-MRD and hyperleukocytosis remained independently associated with inferior RFS, EFS, and OS. A combination of PI-MRD-positive status and hyperleukocytosis identified the patients with the worst clinical outcomes. Conclusion: Detectable PI-MRD using MFC was found to be the strong predictive factor of inferior clinical outcome in TALL patients. The combination of PI-MRD status and hyperleukocytosis provides the most influential tool for the management of TALL in resource constrained settings from developing world.

No abstract