ESTRO 2024 - Abstract Book

S1140

Clinical - Haematology

ESTRO 2024

908

Digital Poster

Radiotherapy in Diffuse Large B Cell Lymphoma: Retrospective Analysis Post-R-CHOP Chemotherapy

Jaeha Lee, Sang-wook Lee, Si Yeol Song, Young Seob Shin

Asan Medical Center, Radiation Oncology, Seoul, Korea, Republic of

Purpose/Objective:

This retrospective study aimed to provide a nuanced understanding of the role of salvage radiotherapy in Diffuse Large B Cell Lymphoma (DLBCL) patients following R-CHOP chemotherapy, particularly in scenarios where conventional treatment completion is challenging.

Material/Methods:

In this retrospective study spanning January 2010 to January 2020 at ASAN Medical Center, we analyzed data from 205 DLBCL patients who underwent radiotherapy following R-CHOP chemotherapy. The exclusion of recurrent and palliative cases aimed to focus on treatment-naïve individuals, ensuring a precise evaluation of radiotherapy's impact in newly diagnosed DLBCL. Analyses, stratified by R-CHOP cycles and disease characteristics, along with survival analyses and subgroup assessments, were conducted to identify potential prognostic factors, notably cell of-origin classification.

Results:

Data from 108 treatment-naïve DLBCL patients who underwent salvage radiotherapy post-R-CHOP at ASAN Medical Center between January 2010 and January 2020 were analyzed. Stratification based on the number of R-CHOP cycles revealed that 27 patients received 4 or fewer cycles, while 81 patients received 5 or more cycles. Notably, patients receiving 4 or fewer cycles demonstrated a high prevalence (81%) of head and neck tumors, and 85% had Ann-arbor stage 2 or lower. After R-CHOP, complete responses were achieved in 49% of patients, and partial responses in 43%. Remarkably, regardless of R-CHOP cycle, 85% of patients attained a complete response after salvage radiotherapy. The 5-year overall survival rate stood at 78.7%, with an event-free survival rate of 76.4% for all stages. In-depth analyses of chemotherapy responses revealed a 3-year overall survival rate of 88.2% for complete responders, 79.1% for partial responders, and 22.2% for those with progressive disease. Subgroup analysis based on cell-of-origin classification (GCB vs. non-GCB) unveiled a statistically significant difference in the 5-year survival rates - 91.3% for GCB type and 72.2% for non-GCB type (p=0.036). However, no statistically significant difference in 5-year event-free survival was observed. Further subgroup analysis focusing on 58 patients with AAS stage I-II and IPI 0-2 indicated a robust 5-year overall survival rate of 90.9%, with an accompanying 5-year event-free survival rate of 83.2%. Importantly, the survival difference based on chemotherapy response in this subgroup was not statistically significant — 93.6% in complete