Emerging evidence suggests existence of three prognostically relevant molecular entities among immature T-ALL-early thymic precursor ALL (ETP-ALL), T-ALL with the absence of biallelic deletion of TCRγ chains (ABD) and MEF2C (Myocyte Enhancer Factor 2C) high T-ALL. However, the usefulness of ETP-ALL immunophenotype and assessment of ABD for this purpose has been questioned and, MEF2C has not been studied in much detail. In this prospective analysis of 143 T-ALL patients, we evaluated the mutual association of these three entities and also determined how immunophenotypically-defined poor prognosis immature T-ALL relates to these entities. We found that all three of them, especially ABD, nearly completely characterized the immature group. High MEF2C expression reflected ETP-ALL somewhat poorly and a few ABD and MEF2C-high patients had non-immature immunophenotype-findings, that though in accord with published literature, call for exploration per T-cell receptor (TCR) classification scheme. ETP-ALL and MEF2C high but not ABD had a higher frequency of minimal residual disease positivity and poor event-free survival. MEF2C high, not ETP-ALL immunophenotype or ABD, had poorer overall survival. The value of ETP-ALL immunophenotype and MEF2C status, as indicators of poor treatment response, needs further evaluation for possible incorporation in standard T-ALL management practice.
Keywords: ABD; ETP-ALL; MEF2C; T-ALL.
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