Allogeneic stem cell transplantation for major T-cell lymphoma entities: an analysis of the EBMT-lymphoma working party

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (allo-SCT) is an established treatment for peripheral T-cell lymphoma (PTCL), particularly for patients with relapsed/refractory (r/r) disease. We aimed to retrieve novel information on the role of histology, disease status prior to transplantation, and donor choice for patients with PTCL not otherwise specified (NOS), angioimmunoblastic T-cell lymphoma (AITL), and anaplastic lymphoma kinase (ALK)-negative ALCL. We compared imaging by computed tomography (CT) or positron emission tomography (PET) for defining disease status prior to allo-SCT. METHODS: Eligible were adult patients with PTCL-NOS, AITL, and ALK-negative ALCL undergoing allo-SCT between 2010 and 2022 and reported to EBMT. RESULTS: 1958 patients underwent allo-SCT. Of patients with known number of prior lines of therapies (n = 1310), 301 (23%), 431 (32.9%) and 578 (44.1%) patients received allo-SCT after one (1L), two (2L) or three or more therapy lines (3L +), respective. Three-year GvHD-free, relapse-free survival (GRFS), progression-free survival (PFS) and overall survival (OS) were 35.8%, 50.9% and 56.8%, respectively. Three-year relapse incidence (RI) and non-relapse mortality were 25.1% and 24.1%, respectively. In multivariate analysis, histology other than AITL, no complete response (CR) at transplantation, having a haploidentical donor and higher age at allo-SCT resulted in significantly lower PFS and/or OS. Prior autologous SCT had no impact on the results of allo-SCT and major outcomes did not significantly change when the analyses were restricted to the patients with PET-based response at allo-SCT. Patients allografted in partial response (PR) or SD/PD still achieved long-term survival with a 3-year PFS/OS of 46%/53.7% and 39.6%/43.6%, respectively. CONCLUSION: Allo-SCT is a valid treatment option in relapsed/refractory PTCL where targeted therapies still play a limited role. Patients with AITL survived significantly better than patients with PTCL NOS or ALK-negative ALCL following a significantly lower RI, also when comparing CR/complete metabolic response (CMR) and PR patients separately. Higher age and non-CR at allo-SCT are associated with worse outcomes.