ESTRO 2025 - Abstract Book

S907

Clinical - Haematology

ESTRO 2025

Kim, Ha, et. al. (2024). Skin-directed radiotherapy for primary cutaneous T-cell lymphomas. Radiation Oncology Journal. 42. 228-236. 10.3857/roj.2024.00444. 3766 Mini-Oral 5-5-5 ABRT (Adaptive Bridging Radiation Therapy) – Artificial Intelligence Enters the CAR (-T) in Rel/Ref Large B-Cell Lymphoma (Trial: NCT06004167) Chirayu G Patel 1 , Hazim S. Ababneh 1 , Andrea K. Ng 2 , Joshua Wan 1 , Tyler Walburn 1 , Lin Zhu 1 , Mislav Bobic 1 , P. Connor Johnson 1 , Jeremy Bredtfeld 2 , Jacob Soumerai 1 , Jeremy Abramson 1 , Jeffrey Barnes 1 , Ronald Takvorian 1 , Matthew J. Frigault 1 , Jennifer Pursley 1 1 Radiation Oncology, Massachusetts General Hospital, Boston, USA. 2 Radiation Oncology, Brigham and Women's Hospital, Boston, USA Purpose/Objective: Bridging radiation therapy (BRT) is effective for local control in patients with relapsed or refractory large B-cell lymphoma (LBCL) who are undergoing CAR T-cell therapy. We hypothesized that adaptive bridging RT (ABRT), which can be used to personalize the radiation dose, fractionation, and volume based on real-time lymphoma target volume, is feasible, safe, and effective for local control. Material/Methods: We conducted a pilot study to investigate, once weekly, CT-based adaptive RT (Varian Ethos) at a dose of 5 Gy per fraction for up to 5 fractions over 5 weeks (‘5-5-5’) in patients referred for BRT (NCT06004167). Results: Ten patients were enrolled. Twelve sites were irradiated for palliative purposes, achieving an overall symptomatic response rate of 100%. Of the 40 total ABRT sessions, 26 fractions were delivered (65%). For 8 of the 11 target volumes treated, ABRT was held after the first one or two fractions. The in-field responses during ABRT pre-CAR T were: CR (n=3, 30%), PR (n=6, 60%), and in-field progression (n=1, 10%). Following CAR T-cell infusion, the best overall response rate (ORR) was 70% (n = 7), all of whom achieved CR. Among all 10 patients, three experienced in field recurrence following start date of BRT. Grade 3 immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 50% (n = 3). No grade 3 or higher cytokine release syndrome (CRS) events were reported. At the time of the last follow-up, 9 patients (90%) were still alive, and 1 patient (10%) died due to disease progression. Conclusion: We demonstrate the safety and feasibility of the ‘5-5-5 ABRT’ approach in this highly relapsed/refractory population, even in patients with high-volume disease, with the vast majority responding to 1 to 2 fractions of 5 Gy. All patients achieved symptomatic relief and were able to proceed to CAR-T cell infusion.

Keywords: radiation, CAR T-cell therapy; bridging therapy

3920

Digital Poster Clinical outcome and health-related quality of life after chemo-immunotherapy and ISRT in early nodal DLBCL- long-term results of a phase II trial Ahitagni Biswas 1 , Swarnaditya Roy 1 , Ashish Binjola 1 , Madhavi Tripathi 2 , Rajeev Kumar Malhotra 3 , Sameer Bakhshi 4 , Ranjit Sahoo 4 , Ajay Gogia 4 , Atul Sharma 4 , Chandrasekhar Bal 2 , Suman Bhasker 1 1 Radiation Oncology, All India Institute of Medical Sciences, New Delhi, New Delhi, India. 2 Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, New Delhi, India. 3 Delhi Cancer Registry, All India Institute of Medical