ESTRO 2024 - Abstract Book

S5175

Radiobiology - Immuno-radiobiology

ESTRO 2024

Results:

Significantly increased quantities of proliferating CD8 T cells were evident in all radiation exposure categories within the immunotherapy plus CRT cohort compared to patients treated only with CRT (p=<0.0001, p=0.02, p=<0.0001 for low, intermediate, and high dose respectively). Additionally, higher numbers of activated Tregs were observed in TDLN receiving high-doses. Furthermore, a dose-dependent relationship was noted, with higher radiation dose resulting in increased numbers of activated CD8 T cells and Tregs (INCREASE high dose vs low dose, p=0.0095 for CD8 and p=0.0298 for Tregs, control intermediate dose vs low dose p=0.0322 for CD8). No significant differences in cytotoxic T cell apoptosis between the two cohorts were observed. Spatial transcriptomics profiling using GeoMX demonstrated a marked type-1 cell-mediated immune response in the INCREASE cohort. Furthermore, increased expression of genes related to nucleosome organization, E2F targets, and the extracellular matrix, as well as radiation-induced collagen IV and histone gene upregulation, suggested elevated fibrosis and tissue repair following high-dose radiation.