ESTRO 2024 - Abstract Book

S5245 ESTRO 2024 Yolanda Prezado 1 , Charlorte Lamirault 1 , Cristele Gilbert 1 , Julie Espenon 1 , Annaig Bertho 1 , Lorea Iturri 1 , Gabriel Ramasay 1 , Ludovic De Marzi 1 , Nils Warfving 2 , Klaus Weber 2 , Frederic Pouzoulet 1 , Marjorie Juchaux 1 Radiobiology - Normal tissue radiobiology

1 Institut Curie, Translational research, Orsay, France. 2 Anapath, Anapath, Bern, Switzerland

Purpose/Objective:

The reirradiation number increased due to systemic therapies and patient survival. Few guidelines regarding acceptable cumulative doses to organs at risk (OARs) and appropriate dose accumulation tools need, made reirradiation challenging. One of the main concerns is patients’ safety. Along this line, some innovative radiotherapy approaches might offer a promising alternative for re-irradiations. Proton minibeam radiation therapy (pMBRT) [1] is a novel technique based on a highly spatially modulated dose distributions which activates distinct biological mechanisms. As a result, pMBRT has demonstrated in several preclinical experiments to lead to a superior tumor control compared to conventional proton therapy while remarkably sparing normal tissues [2-5]. In this study we wanted to test the hypothesis that pMBRT would also spare normal tissues in the context of re-irradiations.

Material/Methods:

Thirty-two male 7 weeks old Fischer rats were including in the study. Four groups of 8 animals were considered: i) a control group; ii) a group receiving whole brain irradiation (excepting olfactory bulb) with conventional radiotherapy (20 Gy); iii) a third group who received a second conventional irradiation 2 months after the first one (20 Gy); iv) a fourth group in which the second irradiation was performed with pMBRT (20 Gy average). The animals were followed up for six months. Behavioural tests were performed at 3 and 6 months after irradiation. Anatomopathological evaluation were also carried out.

Results:

Behavioural tests showed significant impact on memory when the second irradiation was a conventional one, contrary to pMBRT. pMBRT also prevented anxiety. The anatomopathological evaluations revealed extensive brain damage, including radio necrosis, when the re-irradiation was a conventional in contrast to pMBRT re-irradiation.

Conclusion:

The reduced side effects observed after pMBRT re-irradiation compared to conventional one suggests that pMBRT is a promising alternative for re-irradiations.

Keywords: re-irradiation, brain, proton minibeam radiation

References:

1. Prezado, Y. and G.R. Fois, Proton-minibeam radiation therapy: a proof of concept. Med Phys, 2013. 40(3): p. 031712.

2. Prezado, Y., et al., Proton minibeam radiation therapy spares normal rat brain: Long-Term Clinical, Radiological and Histopathological Analysis. Sci Rep, 2017. 7(1): p. 14403.