Clinical Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation in Children with T Cell Acute Lymphoblastic Leukemia/Lymphoma.

T cell acute lymphoblastic leukemia (T-ALL) and lymphoblastic lymphoma (T-LBL) in pediatric patients remain a high-risk hematologic malignancy with suboptimal outcomes in relapsed or refractory cases. Allogeneic hematopoietic stem cell transplantation (HSCT) is considered a potentially curative option, particularly for children with poor prognostic factors or refractory patients. In this retrospective study, we evaluated transplant outcomes in 135 pediatric patients (128 diagnosed with T-ALL and 7 with T-LBL). Isolated bone marrow involvement was documented in 100 cases, isolated extramedullary disease in 13 cases, and combined bone marrow and extramedullary involvement in another 22 patients. The cohort included recipients of related fully matched, unrelated, and haploidentical transplants, as well as different GVHD prophylaxis strategies (ex vivo T cell depletion and pharmacological prophylaxis). These factors were not considered exclusion criteria, as the primary focus of the present analysis was the assessment of relapse risk and its predictors. The 5-year cumulative incidence of non-relapse mortality was 7.6%, and of relapse or progression was 26%. The 5-year event-free survival (EFS) was 63%, and the 5-year overall survival (OS) was 65%. The principal factor influencing outcomes was active disease at the time of HSCT. In the cohort of patients transplanted in complete remission (CR), OS and EFS rates were 73.3% and 72.8%, respectively.