ESTRO 2025 - Abstract Book

S903

Clinical - Haematology

ESTRO 2025

Patients were selected for either pathway A (bridging single-modality RT) or B (systemic therapy bridging and cRT). Pathway A was selected if RT was feasible to cover all or most disease sites (using 2-dose levels 20-40Gy for high-risk and 4Gy for other sites), whereas pathway B was for rapidly progressing and wide-spread extranodal disease. Indications for cRT were high-risk lesions on baseline PET-CT (≥5cm and/or SUVmax ≥15) which showed a Deauville score 3-4 or 5 (partial response) on 1-month PET-CT. cRT was planned 6-8 weeks post CAR-T using CAR-T-sparing techniques. These included: 1) contouring and dose-optimisation of blood vessels and blood-rich OARs to reduce doses to blood, and 2) measures to reduce beam-on time (hypofractionation, limited beam angles, flattening filter free beams). Results: 50 patients received RT, 28 in pathway A and 22 in pathway B. Median age was 56 years (range 20-79). 52% had stage III-IV (32% pathway A, 77% pathway B), 37% bulky disease, 16% ≥2 extranodal sites, and 12% high LDH. The median RT dose was 30Gy in both pathways (20-36Gy/10-15# and 25-37.5Gy/5-15# in A&B, respectively). One patient in pathway A did not receive CAR-T due to PD (overall protocol completion 98%). Median needle-to needle time was 36 days (43 and 35 for pathway A&B, respectively). Overall response rate at 1 month was 89.4% (51.1% DS 1-3) and 75.7% at 6 months. With a median follow-up of 12.1 months, 9 patients progressed (4 pathway A and 5 pathway B) and 5 died, all due to PD. Overall 1-year PFS (intention-to-treat analysis) was 63% (95%CI 49-76) and OS was 85% (95%CI 75-95) (Figures 1,2). Significant toxicity included 5 grade-3 ICANS but no CRS grade≥ 3. No grade≥3 toxicity was reported after cRT.