Assessment of the Quality of Radiation Treatment Planning for Patients with Glioblastoma During the Transition to a Hypo Fractionation Regime.

Purpose: To evaluate the quality of radiation treatment plans and dose loads on critical structures of patients with glioblastoma during the transition from a standard RT regimen to hypofractionation. Мaterial and methods: The study included 93 patients with glioblastoma who underwent radiation treatment at the electron accelerator Clinac iX from 2014 to 2022 using intensity-modulated radiation therapy (IMRT) or three-dimensional conformal radiotherapy (3D-CRT). The calculation of irradiation plans was carried out on Eclipse planning systems using dose-volume histograms. Depending on the fractionation regimen, patients were divided into two groups. Forty-three patients received treatment using the standard fractionation regimen, and 50 patients received hyperfractionation. In the standard fractionation group, 40 patients received the classical regimen with RD = 2 Gy and 30 fractions, as well as modified regimens: 2 Gy × 26 ( 52 Gy), 2 Gy × 18 ( 36 Gy), and 2 Gy × 17 ( 34 Gy), which is associated with an individualized approach to dosing. A total of 132 courses of radiation therapy were administered, which is explained by the presence of multi-stage treatment in some patients. Dose restrictions for critical structures are based on the data of the international protocols QUANTEC, RTOG, and the recommendations of R. Timmerman Results: Homogeneity indices (HI) and conformity indices (CI) were calculated. An analysis of dose loads on critical structures revealed that safe doses to the chiasm and optic nerves are achieved using single-stage hyperfractionation approaches. The lowest doses are also observed for the crystalline lens (left and right). Based on the results of the analysis of the homogeneity and conformity indices and the dose loads on critical structures, it can be said that the best fractionation mode is single-stage hypofractionation, which provides an optimal balance between homogeneity, conformity and safety for the critical structures of the visual organs.