ESTRO 2022 - Abstract Book

S985

Abstract book

ESTRO 2022

Results Of ten patients, 7 were females. The median age was 7 years (range 3 to 17 years). For almost all dosimetric variables, proton plans showed a statistically significant dosimetric advantage in OAR variables, including to the optic nerves and chiasm, cochleae, pituitary gland, hypothalamus, hippocampi, temporal lobes, brain and brainstem. The mean D0.03cc for brainstem, skin and spinal cord were not statistically significantly different between modalities (Figure 1). The mean integral dose was significantly lower in protons compared to photons (p=0.00) with a median proton to photon integral dose ratio of 0.55 (range-0.41 to 0.74). The mean percentage of the PTV receiving 95% of prescription dose and the mean homogeneity index were not statistically significantly different between proton and photon plans (p=0.11 and p=0.98 respectively, Table 1).

Conclusion This study showed marked dosimetric advantage for protons in OAR sparing and lowered integral doses, while maintaining similar target volume coverage. This is anticipated to reduce the risk of late effects, particularly hearing loss, endocrine dysfunction, neurocognitive effects, and second malignancies, while maintaining the established high rates of local control with photons.

PO-1162 MRI texture analysis of radionecrosis and isodoses levels after radiosurgery in brain metastases

S. Fernandez Alonso 1 , I. Casado Ruiz 2 , S. Guardado Gonzales 1 , G. Pozo 3 , R. D´Ambrosi 1 , P. Adaimi 3 , E. Cabello 3 , M.A. Perez Escutia 1 , J.F. Perez-Regadera 1 1 Hospital Universitario 12 de Octubre, Radiation Oncology, Madrid, Spain; 2 Universidad Politécnica de Madrid, Photonic Technology and Bioengineering, Madrid, Spain; 3 Hospital Universitario 12 de Octubre, Radiophysics, Madrid, Spain Purpose or Objective To quantitatively analyze the relationship between the appearance of radionecrosis (RN) and isodoses levels, comparing textural features between these regions.