Allogeneic Stem Cell Transplantation in Mantle Cell Lymphoma; Insights into Its Potential Role in the Era of New Immunotherapeutic and Targeted Therapies: The GETH/GELTAMO Experience

SIMPLE SUMMARY: We present the long-term results of patients receiving allogeneic stem cell transplantation (allo-SCT) for relapsed/refractory mantle cell lymphoma (R/R MCL) in the last 25 years in Spain. We conclude that allo-SCT may be a curative option in R/R MCL with a low cumulative incidence (CI) of relapse, although non-relapse mortality (NRM) is still high, which is mainly secondary to acute graft-versus-host disease (aGVHD). Results are better for fit patients, using HLA-identical (related or unrelated) or haploidentical related donors and without previous ASCT. However, the arrival of new highly effective and low toxic immunotherapeutic or targeted therapies inevitably will relegate allo-SCT to those fit patients who fail these therapies, being administered far away from the optimal timing. ABSTRACT: Allo-SCT is a curative option for selected patients with relapsed/refractory (R/R) MCL, but with significant NRM. We present the long-term results of patients receiving allo-SCT in Spain from March 1995 to February 2020. The primary endpoints were EFS, OS, and cumulative incidence (CI) of NRM, relapse, and GVHD. We included 135 patients, most (85%) receiving RIC. After a median follow-up of 68 months, 5-year EFS and OS were 47 and 50%, respectively. Overall and CR rates were 86 and 80%. The CI of relapse at 1 and 3 years were 7 and 12%. NRM at day 100 and 1 year were 17 and 32%. Previous ASCT and Grade 3–4 aGVHD were associated with a higher NRM. Grade 3–4 aGVHD, donor type (mismatch non-related), and the time-period 2006–2020 were independently related to worse EFS. Patients from 1995–2005 were younger, most from HLA-identical sibling donors, and were pretreated less. Our data confirmed that allo-SCT may be a curative option in R/R MCL with low a CI of relapse, although NRM is still high, being mainly secondary to aGVHD. The arrival of new, highly effective and low toxic immunotherapeutic or targeted therapies inevitably will relegate allo-SCT to those fit patients who fail these therapies, far away from the optimal timing of treatment.