ESTRO 2024 - Abstract Book

S5237

Radiobiology - Normal tissue radiobiology

ESTRO 2024

512

Proffered Paper

Proton minibeam radiation therapy: elucidating in vivo mechanisms with infrared microspectroscopy

Roberto González-Vegas 1 , Ibraheem Yousef 2 , Olivier Seksek 3 , Ramon Ortiz 4 , Annaïg Bertho 4 , Marjorie Juchaux 4 , Catherine Nauraye 5 , Ludovic De Marzi 5 , Annalisa Patriarca 6 , Yolanda Prezado 4 , Immaculada Martínez-Rovira 1 1 Autonomous University of Barcelona, Ionising Radiation Research Unit, Physics Department, Cerdanyola del Vallès (Barcelona), Spain. 2 ALBA-CELLS Synchrotron, BL01 - MIRAS Beamline, Cerdanyola del Vallès (Barcelona), Spain. 3 Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France. 4 Institut Curie, Signalisation Radiobiologie et Cancer, Orsay, France. 5 Institut Curie, Université Paris-Saclay, Radiation Oncology, Orsay, France. 6 Centre de Protonthérapie d’Orsay, Radiation Oncology, Orsay, France

Purpose/Objective:

Proton minibeam radiation therapy (pMBRT) is a novel oncological treatment modality that encompasses the use of proton beams with a spatial fractionation of the dose, resulting in arrays of submillimetric beamlets. pMBRT was proposed to address current limitations of conventional radiotherapy (RT). Preclinical studies proved that this type of fractionation permits using high doses while preserving healthy tissues and maintaining tumour control [1, 2]. Nevertheless, the biochemical processes involved in pMBRT are not yet fully understood. In this context, one way to examine the possible biochemical mechanisms involved in this therapeutic modality is through the use of Fourier transform infrared microspectroscopy (FTIRM). This non-destructive technique is based on the light absorbance due to the vibration of the molecular bonds [3]. By allowing an infrared (IR) radiation beam to pass through a set of biological samples, their corresponding absorbance spectra can be measured and compared; hence, details about the biochemical content and structure of the main biomolecules and their possible conformational modifications can be unveiled. FTIRM has already proven useful in determining the response of cells and tissues to various treatment modalities, including RT [4]. Therefore, the present study aims to report biochemical insights for in vivo pMBRT irradiations using FTIRM for the first time. RT irradiations were performed at the Institut Curie Proton Therapy Center (Orsay, France). Both healthy and glioma-bearing (F98 cell line) Fischer 344 rats were subjected to conventional broad beam (BB) and spatially fractionated proton RT. Whole brain irradiations (excluding the olfactory bulb and cerebellum) were performed, with a prescribed mean dose of 30 Gy; for pMBRT, the previous value refers to the mean dose of the lateral profile of the minibeams, with peak and valley doses of 59 ± 2 Gy and 14.5 ± 1.0 Gy, respectively. Brain tissue sections were fixed at 2 hours and at 24 hours post-RT for healthy rats, and at 24 hours post-RT for tumour-bearing rats. FTIRM measurements were then conducted at the MIRAS beamline of ALBA-CELLS Synchrotron, where IR raster scanning maps of the whole rat brain sections were collected for each sample and irradiation conditions (2 controls, 2 BB-irradiated, and 2 pMBRT-irradiated). Data analysis was performed using Quasar [5], and included the generation of hyperspectral images and the probability density assessment of various spectral ratios, used as markers of biochemical modifications [4]. Material/Methods:

Results:

Hyperspectral imaging revealed the distribution of the analysed spectral markers according to the brain region and irradiation configurations. Important differences were found between control and irradiated healthy animals