expression, but not absence of bi-allelic deletion of TCR gamma chains (ABD), is a predictor of patient outcome in Indian T-acute lymphoblastic leukemia.

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 (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, 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 expression reflected ETP-ALL somewhat poorly and a few ABD and -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 high but not ABD had a higher frequency of minimal residual disease positivity and poor event-free survival. high, not ETP-ALL immunophenotype or ABD, had poorer overall survival. The value of ETP-ALL immunophenotype and status, as indicators of poor treatment response, needs further evaluation for possible incorporation in standard T-ALL management practice.