Evaluation of Anatomical and Dosimetric Changes in the Tumor and Organs at Risk During Radiotherapy with a Tomotherapy Device for Brain Tumors and Investigation of the Necessity of Adaptive Radiation Therapy

Abstract

Background: There are different opinions about anatomical and dosimetric changes during radiotherapy of brain tumors. The aim of this study was to evaluate anatomical and dosimetric changes of the tumor and organs at risk (OARs) during radiotherapy and to assess the necessity of adaptive radiotion therapy (ART). Methods: This cross-sectional descriptive-analytic study was conducted on 44 patients with brain tumors treated with helical tomotherapy. Differences in planning target volume (PTV) and OARs’ volume and dose were obtained at the treatment planning stage, the first and last treatment fractions. The difference between the actual cumulative doses at the last fraction and the initial planned doses was used to evaluate ART necessity. Findings: Up to 9.09 of all patients with brain tumors received an overdose to some of their OARs (brainstem) due to anatomical changes during radiotherapy and required ART. About 20.45 of all patients received a dose above the tissue tolerance level due to the proximity of their OARs to the tumor at the treatment planning stage, and the volume and dose changes during radiotherapy did not cause this overdose. Conclusion: Considering how much anatomical changes lead to each organ receiving a dose that exceeds its tolerance, a small percentage of patients needed ART. On the other hand, reducing the time interval between simulation and the first treatment session could play a more significant role in reducing differences during radiotherapy stages. © 2025, Isfahan University of Medical SciencesIUMS. All rights reserved.