T-ALL Minimal Residual Disease Using a Simplified Gating Strategy and Its Clinico-hematologic Correlation: A Single Center Experience from North India

The presence of minimal residual disease (MRD) is one of the strong predictors of disease outcome in various hematological malignancies including B-ALL and T-ALL, independent of pre-therapeutic risk factors. There is scant Indian data on MRD by flowcytometry in T-ALL including gating strategies, clinical correlation etc. The primary aim of this retrospective observational study was to define the clinico-hematologic characteristics and prognostic significance of patients with ETP/near-ETP versus non-ETP immunophenotype, especially in terms of minimal residual disease at different time points as well as event-free survival (1 year). Baseline hematologic characteristics along with post-induction (Day-35) and post-consolidation (Day-78) MRD in bone marrow samples from newly diagnosed T-ALL patients were studied. 14.3% patients had ETP-ALL immunophenotype, 11.4% were near-ETP ALL patients and the remaining 74.5% were of non-ETP subtype. The ETP/near ETP patients was significantly associated with higher risk of MRD positivity ( > 0.01%) at the end of induction in comparison to the non-ETP patients ( p  = 0.033). Also, these patients showed a trend towards proclivity to anemia ( p  = 0.06) and higher rates of induction failure ( p  = 0.07) However, no difference was observed between the two subgroups in terms of age, high TLC, thrombocytopenia, adverse cytogenetics, steroid responsiveness on Day + 8 of induction, MRD-positivity > 0.01% at the end of consolidation and EFS-1 year. Through this preliminary study, it can be stated clearly that ETP status is associated with MRD > 0.01% post-induction but has no significant impact on long-term survival of these patients.