Clinical features of immature leukemias in children.

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL), mixed phenotypic acute leukemia (MPAL), and acute myeloid leukemia with minimal differentiation (AML-M0) all originate from immature hematopoietic progenitor cells and have a poor prognosis. We investigated the clinical characteristics of these immature leukemias in 17 children (ETP-ALL: 8, MPAL: 5, AML-M0: 4) at seven institutions. Clinical and laboratory findings were comparable across disease types. Eleven and six patients received ALL- and AML-oriented induction chemotherapy, with six and four achieving complete remission (CR), respectively. Five additional patients achieved CR after salvage with the other type of chemotherapy. Eight patients received hematopoietic cell transplantation (HCT) in first CR, and six survived without relapse. However, six of seven patients who did not receive HCT during first CR relapsed; all underwent HCT later, and only three survived. The 5-year event-free survival (EFS) and overall survival (OS) rate were 37% and 69%, respectively. Patients who achieved CR after induction chemotherapy and received HCT in first CR had favorable EFS and OS. Notably, all patients who received HCT in first CR survived 5 years after diagnosis. Appropriate induction chemotherapy and HCT in first CR could improve the outcome of immature leukemias.