ESTRO 2023 - Abstract Book

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ESTRO 2023

Photon Quality

Cell Line Alpha

Beta

A/B

RBE2Gy/0.1SF

225 kVp (180 kVp for HCT116) HeLa

0.3±0.06 0.055 ± 0.01 4.89± 1.0 1

PC3 0.4±0.04 0.05± 0.006 6.7± 0.9 1 HCT116 0.4±0.06 0.07± 0.01 5.1±1.7 1

HeLa

50 kVp

0.4±0.04 0.05±0.006 7.17±0.9 1.17/1.09

PC3 0.5±0.04 0.05±0.006 9.0±2.1 1.2/1.1 HCT116 0.7±0.04 0.05±0.006 14.2±2.7 1.7/1.3

HeLa

6 MV

0.3±0.06 0.04±0.009 7.46±2.0 0.99/0.95 0.2±0.03 0.06±0.005 3.3±0.6 0.72/0.81 0.2±0.09 0.06±0.02 4.13±2.0 0.95/0.97

PC3

HeLa

192-Ir

PC3 0.2±0.03 0.06±0.004 3.4 ±0.4 0.75/0.84 HCT116 0.4±0.04 0.04±0.005 12.2±2.0 1.08/0.98

Conclusion Clinically, all photons are considered to have an RBE of 1.0. However, in this study we showed that RBE changes for equal absorbed doses delivered with a range of photon energies. RBE increased with decreasing photon energy across all cell lines. Our results show that MV x-rays have lower RBE than 50 kVp x-rays. The cell lines’ intrinsic capacity to repair DNA damage is seen to also play a role in RBE measurements since the 3 cell lines behaved differently for irradiations with identical setups. Further experiments include DNA repair kinetics modeling to better understand the discrepancies seen in RBE values. Additional experiments are underway to study the RBE of 2 additional HNSCC cell lines, with an HPV + or - status, on the qualities mentioned above. High LET alpha particle irradiations will also be performed on all the cell lines.

PO-2226 Transcriptome profiling of tumour samples could predict radioresistance in glioblastoma patients

S. Serrano 1 , G. Antelo 1 , J. Balart 2 , S. Comas 3 , C. Ansón 4 , C. Balañà 5 , A.M. Soto Cambres 2 , I. Valduvieco 1 , S. Villà 3 , M. Mollà 1 , C. Gomà 1 1 Hospital Clínic de Barcelona, Radiation Oncology, Barcelona, Spain; 2 Hospital de la Santa Creu i Sant Pau de Barcelona, Radiation Oncology, Barcelona, Spain; 3 Institut Català d’Oncologia, Radiation Oncology, Badalona, Spain; 4 Hospital de la Santa Creu i Sant Pau de Barcelona, Medical Physics and Radiation Protection, Barcelona, Spain; 5 Institut Català d’Oncologia, Medical Oncology, Badalona, Spain Purpose or Objective Glioblastoma (GB) is the most frequent and aggressive primary brain tumour in adults. Glioblastoma molecular subtypes, Classical (CL), Mesenchymal (MES) and Proneural (PN), have been correlated with prognosis. In the preclinical setting, CL