Eleven‐marker 10‐color flow cytometric assessment of measurable residual disease for T‐cell acute lymphoblastic leukemia using an approach of exclusion

Abstract

Measurable/minimal residual disease (MRD) status has been suggested as a powerful indicator of clinical-outcome in T-cell lymphoblastic leukemia/lymphoma (T-ALL). Multicolor flow cytometric (MFC)-based T-ALL MRD reports are limited and traditionally based on the utilization of markers-of-immaturity like TdT and CD99. Moreover, studies demonstrating the multicolor flow cytometric (MFC) approach for the assessment of T-ALL MRD are sparse. Herein, we describe an 11-marker, 10-color MFC-based T-ALL MRD method using an "approach of exclusion." Methods: The study included 269 childhood T-ALL patients treated with a modified-MCP841 protocol. An 11-marker, 10-color MFC-based MRD was performed in bone marrow (BM) samples at the end-of-induction (EOI) and end-of-consolidation (EOC) time-points using Kaluza-version-1.3 software.Results: We studied EOI-MRD in 269 and EOC-MRD in 105 childhood T-ALL patients. EOI-MRD was detectable in 125 (46.5%) samples (median, 0.3%; range, 0.0007-66.3%), and EOC-MRD was detectable in 34/105 (32.4%) samples (median, 0.055%; range, 0.0008-27.6%). Leukemia-associated immunophenotypes (LAIPs) found useful for MRD assessment were dual-negative CD4/CD8 (40.9%), dualpositive CD4/CD8 (23.3%) and only CD4 or CD8 expression (35.8%); dim/subset/ dim-negative surface-CD3 (39%), dim/subset/dim-negative/negative CD5 (28.3%), dim/dim-negative/negative/heterogeneous CD45 (44.7%) and co-expression of CD5/CD56 (7.5%). EOI-MRD-positive status was found to be the most-relevant independent factor in the prediction of inferior relapse-free and overall survival. Conclusion:We described an 11-marker 10-color MFC-based highly sensitive MRD

Minimal residual disease level determined by flow cytometry provides reliable risk stratification in adults with T‐cell acute lymphoblastic leukaemia

“…It is simpler, faster, less expensive and broader than PCR‐based methods. In our present study, the percentage of detectable FCM‐MRD was 96·9%, consistent with reported rates of 93%, 98% and 100% in patients with T‐ALL 17,21,22 . In addition, it should be noted that our present cohort included some ETP patients and these patients usually lack sensitive PCR markers, 17,23 further emphasising the need for FCM‐MRD monitoring of these patients.…”

“…In addition, they used two‐colour FCM to determine MRD at the time, which was less sensitive and specific than our present six‐ to eight‐colour FCM technology 14 . The relapse rate of our present cohort was higher than that in some previous reports, especially in children 17,22 . Differences in population characteristics and treatment protocols might explain these discrepancies.…”

“…EOI‐MRD was the most powerful predictor of relapse independent of other known risk factors (Table IV). 5,12,17,22,27,28 In our present study, patients who were EOI‐MRD positive had a higher 2‐year CIR than MRD‐negative patients (87·6% vs. 38·8%, P = 0·0020). Although the relapse rate in our present cohort seems high, it was consistent with that previously reported by Krampera et al ., 14 demonstrating that the 2‐year CIR of EOI‐MRD‐positive versus ‐negative patients was 81·5% versus 38·9% in adult patients with T‐ALL.…”

“…EOI‐MRD positivity is the most important independent high‐risk factor for event‐free survival (EFS) and OS in B‐ALL and paediatric T‐ALL (Table IV). 12,22,31 However, in adult T‐ALL, data on the impact of MRD on long‐term outcomes are limited due to its relative rarity 25 . In our present study, adult patients with T‐ALL with EOI‐MRD positivity had inferior RFS and OS compared with MRD‐negative patients (2‐year RFS, 5·4% vs. 61·0%; 2‐year OS, 32·7% vs. 69·7%).…”

“…In our present study, we used 0·01% as a cut‐off value to stratify patients and showed that patients with an EOI‐MRD ≥0·01% had poor clinical outcomes, consistent with published reports that MRD ≥0·01% is clinically significant in predicting the outcome of T‐ALL (Table IV). 12,14,15,17,21,22,25,26,29 These data indicate that FCM is a useful method for MRD assessment and could be adaptable in routine clinical practice for T‐ALL management 7,17,22 …”