Autologous and allogeneic stem‐cell transplantation for transformed Waldenström macroglobulinemia

Introduction: The prognosis of histological transformation (HT) in Waldenström macroglobulinemia (WM) is unfavourable despite the use of diffuse large B-cell lymphoma-directed chemo-immunotherapy. The aim of this study was to evaluate the outcomes after autologous stem-cell transplantation (autoSCT) or allogeneic stem-cell transplantation (alloSCT) in patients with transformed WM. Methods: Patients who received autoSCT or alloSCT between January 1996 and December 2021 were identified in an international multicenter database of 285 patients with transformed WM. The primary end-point was overall survival (OS), calculated from the date of SCT to death from any cause. Secondary end-points were progression-free survival (PFS), incidence of relapse/progression and non-relapse mortality (NRM). Univariate and multivariate analyses were performed using the Cox proportional hazards model for OS and PFS only for the autoSCT cohort, due to the small sample size of the alloSCT cohort. Results: Fifty-six patients were included, 46 had received autoSCT and 10 alloSCT. The median time from HT diagnosis to SCT was 8 months (range, 2–76 months) for autoSCT and 7 months (range, 3–49 months) for alloSCT. The patients received a median of 2 lines of treatment for HT before SCT (range, 1 to 6 for autoSCT and 1 to 3 for alloSCT), and 89% (complete response (CR): 59%) and 80% (CR: 50%) of the patients had chemosensitive disease at the time of autoSCT and alloSCT, respectively. For autoSCT, the conditioning regimen was BEAM in 76% of the patients, and for alloSCT, reduced-intensity conditioning was used in 70% of the cases. The median follow-up time for the surviving patients was 5.5 years (95% CI, 2.8–7.1 years) from autoSCT and 12.6 years (95% CI, 2.7–14.4 years) from alloSCT. The 3-year estimates of OS, PFS and cumulative incidences of relapse and NRM were 57%, 44%, 54%, and 2% for autoSCT and 50%, 50%, 30%, and 20% for alloSCT, respectively. In the autoSCT cohort, CR at SCT was found to be associated with superior OS and PFS (3-year OS, 81% for CR vs. 23% for less than CR, P = 0.001 and 3-year PFS, 62% vs. 21%, P < 0.001) and less than 2 lines of therapy for HT with superior OS (3-year OS, 75% for 1 line vs. 36% for >1 line, P = 0.01). Keywords: Aggressive B-cell non-Hodgkin lymphoma, Stem Cell Transplant No conflicts of interests pertinent to the abstract.