ESTRO 2025 - Abstract Book

S919

Clinical - Haematology

ESTRO 2025

Elsayad K et al. Radiotherapy in cutaneous lymphomas: Recommendations from the EORTC cutaneous lymphoma tumour group. EJC 2024. De Sanctis V et al. Primary Cutaneous Lymphoma: Local Control and Survival in Patients Treated with Radiotherapy. Anticancer Reasearch 2007. Piccinno R. et al. Radiotherapy of primary cutaneous anaplastic large cell lymphoma: our experience in 30 cases. International Journal of Dermatology 2020. Neelis KJ et al. LOW-DOSE PALLIATIVE RADIOTHERAPY FOR CUTANEOUS B- AND T-CELL LYMPHOMAS. IJRBOP 2009. Hristov AC et al. Cutaneous T-cell lymphomas: 2023 update on diagnosis, risk stratification and management. Am J Hematol. 2023

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Digital Poster Risk of Neutropenia With or Without Daratumumab in Bortezomib-Based First-Line Chemotherapy and Radiotherapy for Multiple Myeloma: A Pilot Study Mateusz Pajdziński 1 , Jacek Burzyński 2 , Adam Zięba 1 , Nina Jędrzejczak 1 , Jacek Fijuth 1 , Konrad Stawiski 2 1 1. Department of Teleradiotherapy, Regional Cancer Centre, Copernicus Memorial Hospital of Lodz, Lodz, Poland. 2 2. Department of Biostatistics and Translational Medicine, Medical University of Lodz, Lodz, Poland Purpose/Objective: Significant advancements have transformed the standards of first-line systemic treatment for multiple myeloma in recent years. Despite prior reports, the role of concurrent radiotherapy remains controversial due to concerns about the cumulative toxicity associated with modern combination therapies. Notably, severe neutropenia exacerbated by concurrent radiotherapy may lead to interruptions in systemic therapy. This study aims to evaluate the safety of radiotherapy combined with the addition of daratumumab (DVTx) to first-line bortezomib-based chemotherapy (VTx) in the era of advanced radiotherapy techniques. Material/Methods: This retrospective observational study included patients diagnosed with multiple myeloma who received ionizing radiation during first-line bortezomib-based systemic treatment with (Dara-VTD or Dara-VCD) or without (VCD or VTD) daratumumab at our facility between 2022 and 2024. Laboratory values were recorded for up to 90 days after the completion of both treatments. Patients with pre-existing Grade 3 or higher neutropenia, as defined by CTCAE criteria, before the initiation of radiotherapy were excluded. All patients received 20–30 Gy to bone targets using the RapidArc VMAT technique. Results: A total of 27 patients were eligible for analysis, including 14 treated with VTx and 13 with DVTx. A total of 265 complete blood counts were reviewed. The groups did not differ significantly in terms of age, planning target volume (PTV), or baseline neutrophil counts (p > 0.05). Among the 27 patients, 7 experienced Grade 3 or higher neutropenia during the observation period. The addition of daratumumab to bortezomib-based therapy was not significantly associated with Grade 3 neutropenia during the observation period (Fisher's exact test, p = 0.21; crude OR = 3.75; 95% CI: 0.58–24.28). Grade 3 neutropenia was observed in 5/13 patients receiving DVTx compared to 2/14 patients treated with VTx. Conclusion: The findings suggest that the addition of daratumumab to bortezomib-based first-line chemotherapy does not significantly increase the risk of severe neutropenia in patients receiving concurrent radiotherapy. However, the observed trend toward a higher incidence of Grade 3 neutropenia in the DVTx group highlights the importance of