CD38 is expressed on T-ALL and ETP T-ALL blasts with stable expression following induction chemotherapy and at relapse. (A) Averages of MFI measured by flow cytometry of 21 patients with T-ALL enrolled on the Combination Chemotherapy With or Without Bortezomib in Treating Younger Patients With Newly Diagnosed T-Cell Acute Lymphoblastic Leukemia or Stage II-IV T-Cell Lymphoblastic Lymphoma (AALL1231) study. The gating strategy is described in the supplemental Methods. Gating is on the blast population and therefore represents patients with residual, detectable ALL. (B) MFI of CD38 from 10 T-ALL patients previously enrolled on the Combination Chemotherapy in Treating Young Patients With Newly Diagnosed T-Cell Acute Lymphoblastic Leukemia or T-cell Lymphoblastic Lymphoma (AALL0434) study from initial diagnosis and at first relapse. MFI, median fluorescence intensity.