Volumetric changes in gray matter after radiotherapy detected with longitudinal magnetic resonance imaging in glioma patients

Background and purpose: We evaluated volumetric changes in the gray matter (GM) after radiotherapy (RT) and identified factors that were strongly associated with GM volume reduction.Materials and methods: A total of 461 magnetic resonance imagings (MRI) from 105 glioma patients trea-ted with postoperative RT was retrospectively analyzed. Study patients' MRIs were collected at five time points: before RT and 1 month, 6 months, 1 year, and 2 years after RT. Using the 'FastSurfer' platform, a deep learning-based neuroimaging pipeline, 73 regions were automatically segmented from longitudinal MRIs and their volumetric changes were calculated. Regions were grouped into 10 functional fields. A multivariable linear mixed-effects model was established to identify the potential predictors of signifi-cant volume reduction.Results: The median age was 50 years (range, 16-86 years). Forty-seven (44.8 %) patients were female and 68 (64.8 %) had glioblastoma. Postoperative RT was delivered at 54-60 Gy with or without concur-rent chemotherapy. At 2 years after RT, the median volumetric changes in the overall, ipsilateral, and con-tralateral GM were-3.5%,-4.5%, and-2.4%, respectively. The functional fields of cognition and execution of movement showed the greatest volume reductions. In the multivariable linear mixed model, female sex (normalized coefficient =-0.14, P < 0.001) and the interaction between age at RT and days after RT (normalized coefficient =-6.48e-6, P < 0.001) were significantly associated with GM reduction. The older patients received RT, the greater volume reduction was seen over time. However, in patients with relatively younger age (e.g., 45, 50, and 60 years for hippocampus, Broca area, and Wernicke area, respectively), the volume was not significantly reduced.Conclusions: GM volume reduction was identified after RT that could lead to long-term treatment seque-lae. Particularly for susceptible patients, individualized treatment and prevention strategies are needed.(c) 2022 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 176 (2022) 157-164