Allogeneic hematopoietic cell transplantation in patients with myeloid/lymphoid neoplasm with FGFR1-rearrangement: a study of the Chronic Malignancies Working Party of EBMT.

Allogeneic hematopoietic cell transplantation (allo-HCT) is the only curative treatment for patients with myeloid/lymphoid neoplasm (MLN) with FGFR1 rearrangement, but data on overall results are limited. We report on the largest series of patients (n = 22) with FGFR1-rearranged MLN undergoing allo-HCT. Distribution according to cytogenetic subtype was: t(8;13) in 11 cases, t(8;22) in 7 cases, t(6;8) in 2 cases, and other (n = 2). Over a third of patients displayed a chronic myeloproliferative (MPN) phenotype, another third showed MPN features with concomitant lymphoma or acute leukemia, and the remaining ones presented as acute leukemia. After a median follow-up of 4.1 years from transplant, the estimated 5-year survival rate, progression-free survival, non-relapse mortality and relapse incidence was 74%, 63%, 14% and 23%, respectively. Causes of death were relapse/progression (n = 4), graft-versus-host disease (n = 2) and organ toxicity (n = 1). Six patients experienced disease relapse at a median of 6.1 months (range: 2.3-119.6). Two of them achieved complete remission with ponatinib or pemigatinib and were alive at 34.5 and 37 months from relapse, respectively. These data highlight the significant curative potential of allo-HCT in this aggressive disease. Maintenance with tyrosine kinase inhibitors may be a promising approach, at least in cases with detectable residual disease after transplant.