Current use of donor lymphocyte infusions after allogenic stem cell transplantation in Europe: a survey on behalf of the cellular therapy and immunobiology working party of the EBMT.

Unmanipulated donor lymphocyte infusions (DLI) are crucial for enhancing the graft versus tumor (GVT) effect in post-transplant settings. Practices regarding DLI use vary widely among centers, encompassing differences in indications, prerequisites, and application methods. To explore current DLI policies, we developed a comprehensive survey that garnered responses from 165 EBMT centers across 43 countries. Notably, 97% of respondents reported using DLI in their practices. Indications for DLI included preemptive use for minimal residual disease (MRD) positivity in 86.9% of centers and mixed chimerism in 73.1%; therapeutic use for hematological relapse in 73.1%; and prophylactic use for high-risk disease in 43.8%. Active graft-versus-host disease (GVHD) and active infections were deemed absolute contraindications by 85.6% and 57.5% of centers, respectively. 35% of centers did not consider a prior history of acute (a)GVHD as an exclusion criterion. The majority (71.9%) requested immunosuppression withdrawal before DLI. Most centers (71.3%) collected DLI post-transplant, with 78.1% utilizing unstimulated apheresis. The cell doses applied at the first DLI varied significantly, depending on indication, timing, and donor type. This survey provides the largest overview of current DLI practices, highlighting the need for high-quality data to assess the risks and benefits of different approaches.