Allogeneic HSCT for consolidation in pediatric refractory or relapsed ALK-positive anaplastic large cell lymphoma

Allogeneic hematopoietic stem cell transplantation (HSCT) is used for consolidation in children and adolescents with refractory or early relapsed ALK (anaplastic lymphoma kinase)-positive anaplastic large cell lymphoma (ALCL). The immune system plays a major role in sustained disease control. We retrospectively analyzed whether conditioning, donor type, and in vivo T-cell depletion correlate with outcome in a population-based cohort of 57 children with central nervous system (CNS)-negative ALCL relapse who received HSCT between 2005 and 2022. Progression-free survival (PFS) and overall survival from transplantation were 84% ± 10% and 91% ± 8% at 3 years, respectively. Conditioning was based on total body irradiation (TBI) in 30 patients and on chemotherapy in 27 patients, mainly with reduced-toxicity conditioning (treosulfan, fludarabine, and thiotepa). PFS and graft-versus-host disease (GVHD)-free and event-free survival (GEFS) were comparable between TBI and chemotherapy, 87% ± 6% vs 81% ± 8% (P = .62) and 67% ± 9% vs 74% ± 8% (P = .63), respectively. Patients with transplantation from unrelated donors with rabbit anti-human T lymphocyte globulin (ATLG) had superior PFS and GEFS than those receiving grafts from matched siblings without ATLG: 94% ± 7% vs 67% ± 22% (P = .0007) and 82% ± 13% vs 44% ± 24% (P = .011), respectively. Progression during frontline chemotherapy, minimal residual disease, and remission status at HSCT were not associated with outcome. Nonrelapse mortality was 5.6% for all 65 patients, and cumulative incidence of grade 2 to 4 acute GVHD was 25%. Our data supports the use of TBI-free conditioning and suggest improved outcomes with unrelated donors receiving ATLG prophylaxis.