ESTRO 2022 - Abstract Book

S972

Abstract book

ESTRO 2022

Conclusion IORT for completely resected BM is associated with a promising high local control and low risk of RN, reaching the pre- specified criteria to proceed to the second stage and warranting further studies.

PO-1146 Moderated hypofractionation in brain metastases and cerebral edema

C.F. Carmen 1 , V.B. Victoria 2 , G.D.D. María 2 , B.P. Beatriz 2 , S.S. Paula 2 , R.K. Yesika 2 , Q.R. Juan 2 , R.C. Francisca 2 , M.G. Julia Luisa 2 1 Universitary Hospital Badajoz, Radiation Oncoloy, Badajoz, Spain; 2 Universitary Hospital Badajoz, Radiation Oncology, Badajoz, Spain Purpose or Objective Brain metastases are the most frequent tumors in the central nervous system. Radiotherapy treatment (stereotactic radiotherapy) in a single fraction or in 2-10 fractions (hypofractionated radiotherapy) achieve good results in local control and moderate side effects. The most frequent side effects are edema worsening and radionecrosis (RN). The pathophysiology of brain edema after radiotherapy remains unclear, although many factors could be linked as disruption of the blood-brain barrier, damage to microglia and astrocytes. In general, factors as the PTV volume, irradiation dose and the volume of brain receiving a specific dose are the main risk factors of RN. To evaluate overall survival (OS), progression free survival (PFS) and relationship between the volume edema, volume PTVandtoxicity associated during the hypo fraction treatment and their evolution after treatment, a retrospective study was designed. Materials and Methods Between 2019 and 2021 a total of 12 patients with 17 supratentorial metastases were reviewed. The 50% received radiotherapy to surgical bed, these were treated with total dose of 30 Gy in five fractions every other day and one of them 40Gy in 10 fractions due to the extense volume of treatment. Previous WBRT or radiosurgery were exclusion criteria. To study the relationship between brain volume irradiated and the edema post radiotherapy, the edema volume in both MRI was contoured. In the diagnosis MRI and in the first control (3 months since the end of the treatment). The image fusion was done in the planning system (Pinnacle) using the CT planning with the T2/FLAIR sequence in both MRI. (Fig. 1)