ESTRO 2024 - Abstract Book

S5317

Radiobiology - Tumour biology

ESTRO 2024

Material/Methods:

A549 (epithelial lung carcinoma cells) and MRC5 (normal lung fibroblasts), were treated with fractionated broad beam (BB) and fractionated microbeam (MRT) irradiations. The MRT treatment was performed in two different treatment schemes, one steady MRT irradiation and one MRT irradiation with a 45° rotation of the samples per fraction. All samples were irradiated with one fraction per day for four consecutive days to achieve total doses of 0, 1,2 4, 6, 8 Gy. For both MRT irradiation modalities, the concept of Equivalent Uniform Dose (EUD) was applied. For exact positioning of the cell dishes, a U-shaped plastic stencil was applied to hold the round ibidi μ-Dish in place. The stencil was marked with a pen, indicating positions 0° (1st fraction), 45° (2nd fraction), 90° (3rd fraction and 135° (4th fraction). Cells were analyzed for their survival by the colony formation assay.

Results:

The response of both investigated cell lines differed greatly between the three fractionated irradiation schemes. The cell survival of the lung cancer cell line A549 was significantly reduced at both MRT irradiations modes compared to the conventional BB irradiation (p≤ 0.01). Moreover, the MRT+R irradiation of A549 cells led to a significant lower cell survival BB and MRT without rotation (p≤ 0.01). In the normal tissue cell line MRC, both MRT irradiation modes led to a significantly higher survival rate than in the BB modality. However, MRT without rotation showed the strongest effect when compared to BB (p≤ 0.01).

Conclusion:

Our study clearly demonstrates that the combination of temporal and spatial fractionation has the ability to achieve an increased cell survival in normal tissue cells and at the same time an enhanced cell killing in tumor cells leading to an increased therapeutic index. These results can facilitate the translation of MRT to patients’ treatments by enabling the splitting of the dose into several fractions.

Keywords: MBRT, MRT, tumor growth delay

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Poster Discussion

Effects of minibeam and microbeam radiation therapy on tumor growth delay in human tumor xenografts

Thomas E. Schmid 1,2 , Narayani Subramanian 1 , Jessica Stolz 1 , Aleksandra Colic 2 , Johanna Winter 1 , Mabroor Ahmed 1,2 , Marina Franco 1 , Stefan Bartzsch 2 , Stephanie E. Combs 1,2 1 Klinikum rechts der Isar, Department of Radiooncology, Muenchen, Germany. 2 Helmholtz Zentrum München GmbH, Institute of Radiation Medicine (IRM), Neuherberg, Germany