Outcomes of subsequent neoplasms after umbilical cord blood transplantation in Europe.

Subsequent neoplasms (SNs) compromise long-term survivors after hematopoietic cell transplantion. We performed a retrospective analysis of SNs in a cohort of 10358 recipients of umbilical cord blood transplantation (UCBT) reported to Eurocord/EBMT registries from 1988 to 2018. A total of 233 patients developed SNs. Median age at UCBT was 31 years (y) (0.3-69), and 84 were pediatric patients. Indications for UCBT were malignant hematological diseases in 199 patients (85%). Three groups of SNs were observed. Post-transplant lymphoproliferative disorders (PTLD) were reported in 145 patients in a median of 4 months after UCBT. Of these, 9/145 patients died from relapse, 83/145 from PTLD, and 24/145 from transplant-related causes. At last follow-up, 29/145 were alive; 5y-overall survival (OS) after PTLD diagnosis was 21±3%. Acute leukemia / myelodysplasia (AL/MDS) was diagnosed in 23 patients in a median of 28 months after UCBT and included 3 donor-cell AL. Four of 23 patients died from relapse of primary disease, 8/23 from progression of SNs, and 4/23 from TRM. Seven patients were alive at last follow-up; 5y-OS after AL/MDS diagnosis was 36±10%. Solid tumors (ST) were reported in 65 patients in a median of 54 months after UCBT. Most common tumor sites were lung, thyroid, bone and soft tissue. A total of 33/65 patients died (26 due to ST, 6 to relapse of primary disease, 1 cause missing). At last follow-up, 32/65 patients were alive; 5y-OS after the diagnosis of ST was 51±6%. In conclusion, despite their poor outcomes, SNs that occur after UCBT are extremely rare. Identification of associated risk factors and early detection may help to improve OS.