Donor lymphocyte infusion-based therapy for relapsed adult T-cell leukemia/lymphoma after HLA-haploidentical hematopoietic stem cell transplantation.

Donor lymphocyte infusion (DLI) combined with chemotherapy is an effective therapy for relapsed adult T-cell leukemia/lymphoma (ATL) after allogeneic hematopoietic stem cell transplantation from a human leukocyte antigen (HLA)-matched related donor or matched unrelated donor. The 1-year incidence of ATL relapse is 28 % after HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) with post-transplant cyclophosphamide. However, the efficacy of DLI for relapsed ATL after haplo-HSCT remains unclear. Here, we present the case of a 61-year-old woman diagnosed with ATL who underwent haplo-HSCT from an HLA-haploidentical relative donor. On day +164 after transplantation, the patient experienced ATL relapse. Tacrolimus was tapered and discontinued on day +216; however, ATL progressed. Since the patient did not develop graft-versus-host disease (GVHD) after the discontinuation of tacrolimus, DLI following chemotherapy was performed for relapsed ATL. The patient achieved complete remission without severe GVHD after the 6th DLI treatment. This remission has been sustained for over 15 months with 13 DLI treatments. These results suggest the potential of DLI combined with chemotherapy as a treatment option for patients with relapsed ATL after haplo-HSCT.