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

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.

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

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.

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.

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.