ESTRO 2025 - Abstract Book

S4005

Radiobiology - Tumour radiobiology

ESTRO 2025

Conclusion: While FLASH and CONV-RT are isoeffective against a murine TNBC model, bulk RNA-sequencing data and histology shows that FLASH-RT triggers a higher immune response than CONV-RT. On the contrary, in FLASH irradiated lungs, a decrease in transcription of pro-inflammatory genes was found at early timepoints. These results suggest that FLASH-RT could better stimulate the antitumoral immune response in TNBC without inducing a deleterious inflammatory response in the lungs.

Keywords: Breast Cancer, FLASH

2744

Digital Poster Inhibition of polymerase theta overcomes replication-associated radioresistance in triple-negative breast cancer cell lines Marie Vogt, Sandra Classen, Kerstin Borgmann Department of Radiotherapy & Radiation Oncology, Hubertus Wald Tumor Center-University Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany Purpose/Objective: Despite an initially good response, triple-negative breast cancer (TNBC) tumors develop resistance during therapy. This is attributed to activity of complex DNA repair mechanisms that protect DNA replication. In addition to classical error-free DNA repair processes, numerous error-prone backup mechanisms are responsible for this. The aim of this study was to target DNA replication stress-associated repair processes to further develop new radiotherapeutic interventions and overcome TNBC cell resistance.