Donor lymphocyte infusions as pre-emptive and therapeutic strategy for post-transplant acute lymphoblastic leukemia relapse: A retrospective single-center analysis on 16 consecutive patients

Despite the rapidly evolving landscape, allogeneic transplant still plays a role in acute lymphoblastic leukemia. Relapse post-transplant is not uncommon, leading to dismal prognosis. Donor lymphocyte infusions efficacy in this setting remains controversial. In this retrospective study, we report the use of DLIs in a cohort of 43 ALL (30 B- 13 T-) patients, treated at our Center between 2012 and 2024. 2y-OS, EFS and GRFS were 69.7% (57–85), 44.2% (31–63) and 34.9% (23–52). DLIs were administered in 16 patients. Indication were molecular relapse (44%), hematological relapse (37%) and mixed chimerism (19%). Patients received a median of 4 infusions (1–12), with the first being at a median of 218d (50-1076) post-transplant; median dose was 5.20 × 10 6 CD3+/kg (0.5–50). After DLIs, 2y-OS, EFS and GRFS were 68.8% (49–96), 41.2% (23–75) and 31.2% (15–65), respectively. 2y cumulative incidence of relapse post-DLI was 56.2%. Reasons for not administering DLI in other relapsed patients ( n = 9) were prior GvHD, logistical issues and rapid progression. Outcome was dismal for these patients with 2y-OS of 29.6% (10–87). Overall, our findings suggest that DLIs may retain a role in ALL, particularly when administered in the context of minimal disease burden and when integrated with emerging therapeutic approaches.