ESTRO 2025 - Abstract Book

S914

Clinical - Haematology

ESTRO 2025

Radiation Oncology, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain

Purpose/Objective: To analyze the effect of different combinations of radiotherapy and chimeric antigen receptor T (CAR-Tcell) therapy in lymphomas. Material/Methods: We performed a retrospective observational study of 53 patients treated with CAR-Tcell therapy between 2020 and 2023 at our institution. From this group we select those patients who received radiotherapy at any point of the disease. An analysis of the different combinations, patterns of failure, and outcomes were carried out. Results: A total of 11 patients were eligible for the study. Five patients received salvage radiotherapy (radiotherapy after relapse or refractory to CAR-T cell therapy), 2 patients had bridging radiotherapy, 3 both (bridging and salvage) and 1 palliative treatment. The median age was 48 (20-71), patient’s characteristics are described in table1. Median time from apheresis to infusion was 32 days. The two patients that received exclusive bridging radiotherapy to bulky sites had complete response with a median follow up of 25 months. Patients with salvage radiotherapy: 2 had complete response and 3 progressions outside the field with a median time to progression of 12.53 months. From the group of both: 2 had progression outside the field, are dead from disease with a median follow up of 3 months. From the total group 5 patients progressed all outside the field of radiotherapy, 4 are alive without disease, 4 alive with disease, 3 dead from disease. A Measurement of the total metabolic tumor volume (TMTV) in 18F-FDG PET/CT scans pre CAR-T cell were obtained, from the 5 patients that had progression 3 had the highest TMTV of our cohort, but couldn’t correlate with progression free survival and OS.