ESTRO 2024 - Abstract Book

S5302

Radiobiology - Normal tissue radiobiology

ESTRO 2024

Material/Methods:

Blood samples of patients were collected at Ghent University Hospital before and between 2 to 6 weeks after RT. PBMCs were isolated and cryopreserved until analysis with the G0 cytokinesis-block micronucleus (CBMN) assay. Micronuclei are small nuclear fragments that lag behind during cell division and are a suitable biomarker of radiation induced DNA damage. To assess the chromosomal radiosensitivity before and after RT, PBMCs were also in vitroirradiated with an X-ray dose of 1Gy and further analyzed by the CBMN assay.

Results:

The spontaneous micronucleus (MN) yields present in the majority of the breast cancer patients before radiotherapy fell within the range of spontaneous MN yield observed in healthy individuals. However, there was an increase in spontaneous MN yields observed in most samples collected after radiotherapy, suggesting patient specific chromosomal instability post-treatment. The in vitro radiation response of the patients before radiotherapy was comparable with those of healthy individuals.

Conclusion:

The results showed no differences in the in vitro radiation response of the patients before and after radiotherapy, pointing to the suitability of the CBMN assay as biomarker for individual’s radiosensitivity.

Keywords: Radiosensitivity, Breast cancer, radiotherapy

2833

Digital Poster

Experimental verification of the biological effect of proton minibeam Radiotherapy (pMBRT)

Fardous Reaz 1,2 , Line Kristensen 1,2 , Erik Traneus 3 , Brita Singers Sørensen 2,4 , Niels Bassler 1,2

1 Aarhus University, Dept. of Clinical Medicine, Aarhus, Denmark. 2 Aarhus University Hospital, Danish Centre for Particle Therapy, Aarhus, Denmark. 3 RaySearch Laboratories AB, Dept. of Research, Stockholm, Sweden. 4 Aarhus University Hospital, Dept. of Experimental Clinical Oncology, Aarhus, Denmark

Purpose/Objective:

Spatially Fractionated Radiotherapy (SFRT) offers a novel approach to enhance the efficacy of external beam radiation therapy. Rather than a broad and laterally uniform radiation field, SFRT uses multiple beamlets with a suitable spacing to produce sharp lateral dose gradients. Based on beam size and inter-beam spacing, SFRT can be classified mainly into four groups: GRID radiotherapy, LATTICE radiotherapy, Minibeam radiotherapy~(MBRT), and Microbeam radiotherapy~(MRT) 1 . Proton minibeam radiotherapy (pMBRT), utilizing sub-millimeter beamlets, has emerged as a specialized form of SFRT which possibly might further optimize proton therapy by increasing the therapeutic index [2].The possible advantages of pMBRT to supplement conventional proton therapy have been highlighted in several previous studies 1–5 . However, before considering pMBRT for routine clinical applications, it is crucial to establish its efficacy through pre-clinical studies and to define a set of reference