Allogeneic hematopoietic stem cell transplantation with liposomal mitoxantrone conditioning for extramedullary...

Leukemia relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the leading death cause, with extramedullary disease history as an independent relapse risk factor in acute leukemia. We analyzed 10 patients with extramedullary disease history who received allo-HSCT with mitoxantrone liposome (Lipo-MIT)-containing conditioning at our center (Dec 2022-Jan 2025). Median age was 39.5 (14-63), 7 had acute myeloid leukemia (AML, including myeloid sarcoma), 2 T lymphoblastic lymphoma/leukemia, and 1 B-cell acute lymphoblastic leukemia. Pre-transplant, 4 were in complete remission (CR) (1 with minimal residual disease [MRD] positivity) and 6 had residual lesions (2 with BM blasts ≥ 5%, 2 with MRD positivity). The conditioning regimen was Lipo-MIT + total body irradiation/busulfan + cyclophosphamide ± cytarabine, with a median Lipo-MIT dose of 26.1 (18.5-28.9) mg/m². Mucosal injury showed a high incidence (9/10) after conditioning, but most were transient and controllable with supportive care. Engraftment succeeded in 9 patients, with a median neutrophil recovery time of 16 (11-21) days and platelet recovery time of 20 (11-39) days. Only 1 patient developed grade 2 skin acute graft-versus-host disease (aGVHD). All 9 engrafted patients achieved complete remission (CR) post-transplantation; one had MRD positivity at + 177 days, which turned negative after chemotherapy combined with donor lymphocyte infusion. One patient relapsed at + 234 days and died at + 272 days. The patient with engraftment failure died at + 346 days due to disease progression, with a history of polycythemia vera complicated by myelofibrosis. Lipo-MIT conditioning shows promising efficacy/safety for allo-HSCT in extramedullary disease patients. Randomized trials are needed.