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E. Angelova et al.
has been reported in 10-13% of childhood T-ALL and in 5-17% of adults.5,6 Jain et al. reported significantly poorer outcomes in patients with ETP-ALL, with lower com- plete remission and 5-year overall survival rates, com- pared with other T-ALL patients.6 In the present study, patients with ETP-ALL represented 20% of the T-ALL cohort. We postulate that this high rate of ETP-ALL is likely due, in part, to higher detection rates and to a referral bias to our institution in view of the higher relapse rates of patients with this subtype. Only limited data, using different stratification approaches, are avail- able from other studies on the correlation between CD123 expression and immunophenotype in T-ALL. Lhermitte et al. stratified patients with T-ALL on the basis of a cytoplasmic T-cell receptor β-negative pheno- type and patterns of TRD, TRG and TRB configurations,31 as opposed to commonly used multicolor/multiparame-
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ter flow cytometry immunophenotyping criteria accord- ing to the World Health Organization classification. These authors found that CD123 expression was more common in “immature” T-ALL, being detectable in 68% of adults and 36% of children; in contrast, they identified CD123 expression in 5% of “non-immature” T-ALL cases. Du et al. classified T-ALL patients into “early T- precursor” (CD7+), “T-precursor” (CD2+ and/or CD5+ and/or CD8+), and “mature” (CD3+),30 according to the European Group for the Immunological Characterization of Leukemias (EGIL) criteria. In their study, 83% of cases with an “early T-precursor” immunophenotype were positive for CD123. In keeping with those previous observations, our ETP-ALL group – as well as early-non- ETP – showed the highest frequency of CD123 expres- sion compared with the thymic and mature immunophe- notypes.
B
C
Figure 2. In vitro potency of IMGN632 on leukemic blasts cells and lymphocytes from patients with B-acute lymphoblastic leukemia/lymphoma. (A) The leukemic blast population, but not lymphocyte population, proliferates in culture. (B) IMGN632 is cytotoxic to leukemic blasts from five of eight patients with B-acute lym- phoblastic leukemia/lymphoma (B-ALL), while sparing lymphocytes. (C) IMGN632 eliminates blasts, but not lymphocytes in a specimen (sample H) from a patient with relapsed-refractory B-ALL.
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haematologica | 2019; 104(4)