S527
Clinical - Haemotology
ESTRO 2026
University of Perugia,adiation Oncology Section,Perugia University Hospital,, Perugia, Italy. 6 Department of Medicine and Surgery,, Radiation Oncology Section, University of perugia,, Perugia, Italy Purpose/Objective: Hepatic veno-occlusive disease (VOD) is a rare but serious complication following allogeneic hematopoietic stem cell transplantation (HSCT). Conditioning regimens including total body irradiation (TBI) have been linked to increased hepatic toxicity. Total Marrow and Lymphoid Irradiation (TMLI) provides a more targeted approach, reducing radiation exposure to organs at risk (OARs) such as the liver. This study aimed to evaluate the relationship between liver dosimetric parameters and the occurrence of VOD in patients undergoing TMLI-based conditioning, to identify clinically relevant dose thresholds. Material/Methods: Between August 2015 and April 2024, 90 patients who received TMLI prior to HSCT were retrospectively analyzed. The median age was 56 years (range 21–70). Underlying diseases included acute myeloid leukemia (76%), acute lymphoblastic leukemia (13%), and myelodysplastic syndrome (11%). TMLI was delivered using helical tomotherapy over 4.5 days in nine fractions, prescribing 13.5 Gy to skeletal bones and 11.5 Gy to lymphoid tissues. Liver dosimetric parameters (volume, D ₂ %, D ₉₈ %, Dmean) were extracted using MIM© software (Cleveland, OH). Clinical data on VOD and other acute toxicitieswere collected from patient charts and follow-up visits. Statistical analyses included Spearman’s rank correlation, Mann–Whitney U tests, and ROC curve analysis to identify predictive thresholds for VOD. Results: VOD occurred in 5.6% (5/90) of patients. Those who developed VOD had significantly higher mean liver doses than those without VOD (7.75 Gy vs. 7.18 Gy; p = 0.048). ROC analysis identified a Dmean threshold of 7.57 Gy as predictive of VOD (AUC = 0.665; sensitivity = 80%; specificity = 71.2%). Among 18 transplant-related deaths (20%), two were attributed to VOD. Conclusion: A higher mean liver dose during TMLI conditioning correlates with an increased risk of hepatic VOD. Maintaining the liver Dmean below approximately 7.2 Gy may help prevent this complication and improve post-transplant outcomes. Optimizing liver dose constraints is therefore essential in TMLI planning to minimize radiation-induced hepatic injury and reduce transplant-related mortality. Keywords: TMLI; VOD;Liver dosimetry
and 2025. Patients received either a four-drug regimen (DaraVCD: daratumumab, bortezomib, cyclophosphamide, dexamethasone) or a three-drug regimen (VCD). In total, over 1,500 complete blood count (CBC) records collected during treatment were evaluated to assess hematologic dynamics. Variability in peripheral blood parameters, including white blood cell (WBC), neutrophil, hemoglobin, and platelet counts, was analyzed longitudinally in relation to the start of radiochemotherapy, with special attention to nadir and recovery values. The primary endpoint was the occurrence of grade ≥ 3 neutropenia, while the secondary endpoint was the effect of radiotherapy on stem cell mobilization and the course of autologous hematopoietic stem cell transplantation (auto-HSCT). Results: Patients treated with the four-drug regimen (DaraVCD) showed a distinct dynamic in neutrophil count changes and a significantly higher incidence of grade 3 neutropenia (p = 0.045). Radiotherapy itself did not adversely affect the mobilization process or outcomes of autoHSC (p = 0.456). Conclusion: Concurrent radiotherapy and modern combination chemotherapy may increase the risk of severe neutropenia in MM patients; however, RT does not appear to impair stem cell mobilization or transplantation outcomes. Further multicenter, prospective studies are warranted to validate these findings and to integrate radiomic features into predictive modeling of hematologic toxicity. Keywords: Auto-HSCT, multiple myeloma, treratment efficacy Optimizing Liver Dose Constraints in Total Marrow and Lymphoid Irradiation (TMLI) to Reduce the Risk of Veno-Occlusive Disease Simonetta Saldi 1 , Federico Camilli 2 , Christian Paolo Luca Fulcheri 3 , Claudio Zucchetti 3 , Rebecca Sambenico 4 , Francesco Zorutti 5 , Anna Giulia Becchetti 1 , Loredana Ruggeri 4 , Antonio Pierini 5 , Maria Paola Martelli 4 , Gianluca Ingrosso 6 , Cynthia Aristei 6 1 Department of Medicine and Surgery,, Radiation Digital Poster Highlight 5117 Oncology Section,Perugia University Hospital,, Perugia, Italy. 2 Department of Medicine and Surgery,, Radiation Oncology Section, University of Perugia,, Perugia, Italy. 3 Department of Medicine and Surgery,, Section of Medical Physics,, Perugia, Italy. 4 Department of Medicine and Surgery,, Institute of Hematology and Center for Hemato-Oncological Research (CREO), University of Perugiaation Oncology Section,Perugia University Hospital,, Perugia, Italy. 5 Department of Medicine and Surgery,, Institute of Hematology and Center for Hemato-Oncological Research (CREO),
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