DP010 | POST-TRANSPLANT LYMPHOPROLIFERATIVE DISORDERS: MULTICENTER OBSERVATIONAL RETROSPECTIVE COHORT STUDY OF THE ITALIAN LYMPHOMA FOUNDATION

Background and Aims. Post-transplant lymphoproliferative disorders (PTLDs) are rare complications occurring either after solid organ (SOT) or hematopoietic stem cell (HSCT) transplantation, with an overall incidence of about 1% at 10 years. The Fondazione Italiana Linfomi (FIL) has designed the multicenter observational retrospective cohort study “FIL_PTLD” with the aim to evaluate incidence and management of PTLDs at some Italian hematology centers. Aims include the analysis of clinical characteristics and outcome of patients with PTLD, and the identification of potential variables that may significantly affect disease progression and survival. Results. This retrospective cohort will include patients diagnosed with PTLD from January 2011 to December 2021. Data collection started in October 2024. As of April 2025, 121 patients have been enrolled at 9 active sites. The study will be open at 13 additional Centers in the next few months. The median time from transplant (either SOT or HSCT) to PTLD diagnosis was 7 years. Twenty-three patients had early (diagnosis within 1 year from transplant) PTLD and 98 late (diagnosis after 1-year post-transplant) PTLD. The majority were diagnosed after SOT (95%): after liver (41.7%), renal (36.5%) and heart (16.5%) transplants respectively. Only 4.4% were combined transplants and 6 cases followed a previous HSCT. Most common PTLD subtype was monomorphic PTLD (93.4%): diffuse large B cell lymphoma in 76.9%, Burkitt lymphoma in 5.8%, lymphoplasmacytic lymphoma in 6.6%, marginal cell lymphoma in 1.7% and classical Hodgkin lymphoma in 1.7%. More than 60% of patients presented in advanced stage (Ann Arbor): 18.8% (13 patients) in stage I, 8.7% (6) in stage II, 15.9% (11) in stage III, 46.6% (32) in stage IV. Data on EBER positivity was evaluable in 60 patients: 35.3% (24 patients) showed EBV+ PTLDs; 41.6% in early and 58.3% in late PTLDs. PTLD involved extra-nodal organs in 80.3% of cases. Treatment consisted in reduction of the immunosuppression in 44 (36.4%) patients, with rituximab monotherapy in 60 (49.6%) patients. Data on response and survival will be presented at the meeting. Conclusions. The FIL_PTLD study is the first Italian multicenter retrospective study on PTLDs that will help to improve our knowledge of this rare hematological disorder. New insights may help to improve early diagnosis and timely effective treatment strategies. KEYWORDS: post-transplant lymphoproliferative disorder, EBV.