ESTRO 2025 - Abstract Book

S908

Clinical - Haematology

ESTRO 2025

Sciences, New Delhi, New Delhi, India. 4 Medical Oncology, All India Institute of Medical Sciences, New Delhi, New Delhi, India

Purpose/Objective: Combined modality treatment comprising Rituximab-based chemoimmunotherapy followed by involved field radiotherapy was the standard of care in patients with limited stage diffuse large B-cell lymphoma (DLBCL) at our center. We assessed the feasibility of involved site radiotherapy (ISRT) after chemo-immunotherapy in patients with early nodal DLBCL in a single-arm phase II trial (CTRI/2018/03/012340). Material/Methods: We screened a total of 38 patients with clinically early-stage aggressive B-cell lymphoma at our institute from 15 February-2018 to 15-February-2021, and the database was locked on 4-November-2023 for analysis. 31 eligible patients aged 18-70 years with stage I-II nodal DLBCL and ECOG performance status 0-3 underwent chemoimmunotherapy with R-CHOP21 regimen followed by response assessment 18F-FDG-PET/CT scan. Patients without bulk or B-symptoms underwent 3 cycles of chemoimmunotherapy, whereas 6 cycles were administered in patients with bulk or B-symptoms. Subsequently, they underwent response-adapted ISRT by image-guided IMRT technique. Patients in complete metabolic response (CMR) received 30.6 Gy/17 fractions/3.5 weeks whereas the ISRT dose was escalated to 36 Gy/20 fractions/ 4 weeks in patients with partial metabolic response (PMR). Acute and late RT toxicities were assessed by RTOG acute and late radiation morbidity scoring criteria. Health-related quality of life (QoL) was assessed by FACT-LYM questionnaire at baseline (Qol1), at completion of chemotherapy (Qol2) and at 3(Qol3) and 6(Qol4) months after completion of ISRT. The co-primary endpoints were treatment-related acute toxicity profile and serial changes in QoL parameters. Results: After chemoimmunotherapy, 86.2% and 13.8% of patients attained CMR and PMR, respectively. Overall, 22 (70.96%) patients had grade 3-4 hematological toxicities. Six patients developed febrile neutropenia. Out of 29 patients completing ISRT, 28 (96.66%) attained CMR and 1 had progressive metabolic disease. The incidence of radiotherapy related grade 1-2 hematological and non-hematological toxicities were 44.8% and 93.1%, respectively. Grade 3-4 acute and late radiotherapy toxicities were observed in 1 patient, each. The median follow-up was 55 months. The 5-year local PFS and OS rates were 92.9% and 90%, respectively (Fig 1). There were significant changes in both trial outcome index and total scores at different time points- an initial slow rise in QoL2 followed by a sharp rise in QoL3 and QoL4 due to tumor response and resolution of acute toxicities (Table 1).