Subsequent Neoplasms After Umbilical Cord Blood Transplantation in the Japanese and European Populations.

[BACKGROUND] Subsequent neoplasms (SN) are serious late complications after umbilical cord blood transplantation (UCBT). However, population-based comparisons of the incidence and outcomes of SN between Japan and Europe are lacking.

[OBJECTIVES] To compare the incidence, types, and outcomes of subsequent neoplasms after unrelated UCBT between Japan and Europe.

[METHODS] We conducted a retrospective registry-based study using data from the Japanese Society for Transplantation and Cellular Therapy/Japanese Data Center for Hematopoietic Cell Transplantation and Eurocord/European Society for Blood and Marrow Transplantation. Patients who underwent unrelated UCBT between 1998 and 2018 and later developed SN were included in this study. Patients with Fanconi anemia, Diamond-Blackfan anemia, solid tumors as the primary disease, or those who received combined grafts were excluded. Overall survival (OS) was assessed using the Kaplan-Meier method.

[RESULTS] Among 16,241 (Japan) and 10,358 (Europe) UCBT recipients, 527 (3.2%) and 232 (2.2%) developed SN. The incidence of donor-derived acute leukemia/myelodysplastic syndrome (AL/MDS) was higher in Japan (58%) than in Europe (13%). Solid tumor types differed, with upper gastrointestinal cancers being more frequently observed in Japan (20% versus 5%), while skin (14% versus 8%), thyroid (14% versus 4%), and soft tissue tumors (9% versus 1%) were more common in Europe. Five-year OS after post-transplant lymphoproliferative disorder was significantly higher in Japan than in Europe (48% versus 23%, P < .001), whereas after solid tumors and AL/MDS, it was comparable between the two groups.

[CONCLUSIONS] Marked regional differences exist in SN type and prognosis after UCBT. The observed variations in donor-derived leukemia and solid tumor types underscore the importance of tailored region-specific surveillance strategies for long-term post-transplant care.