Feasibility and Tumor Dynamics of Daily MRI ‐Guided Online Adaptive Radiotherapy for Brain Glioma

BACKGROUND: Magnetic resonance image (MRI)-guided radiotherapy can optimize the therapeutic outcomes of brain glioma patients, as it adjusts to tumor changes in the course of radiation treatment. This study evaluates the dynamic changes of tumors and the feasibility of implementing MRI-guided online adaptive radiotherapy (MRIgOART) for the treatment of brain glioma. PATIENTS & METHODS: This observational prospective cohort study involved patients with brain glioma treated using 1.5 T MR-Linac from 2021 to 2023. MRIgOART can correct treatment errors and evaluate treatment response through adapt-to-position (ATP) and adapt-to-shape (ATS) strategies. Dice similarity coefficient (DSC), absolute/relative volume (Vrel), and Hausdorff distance (HD) metrics were used to quantify tumor changes. The covariables subjected to evaluation included: surgical resection extent, 1p/19q status, telomerase reverse transcriptase (TERT) mutation status, O6-methylguanine-DNA-methyltransferase (MGMT) methylation status, and isocitrate dehydrogenase (IDH) mutation status. ART and non-ART treatment plans were comparatively analyzed based on target coverage and dose constraints for normal brain tissue. The pattern of failure, as the primary endpoint, was evaluated in this study. Secondary endpoints of the study consisted of overall survival (OS) and progression-free survival (PFS), assessed according to treatment schedules. RESULTS: The cohort comprised 57 patients. The patients with an interval longer than 10 days from simulation to the Fx1 exhibited more significant tumor changes (p < 0.001). The tumor volume showed a gradual reduction during the treatment, whereas the alterations in its location and shape became increasingly evident over time. Multivariate analyses identified associations between prognosis and HD, in addition to a relationship between the extent of surgical resection and DSC. ATS was utilized in 52.6% of patients at least once during treatment, with a higher frequency in TERT wild-type patients (p = 0.013). MRIgOART treatment plans achieved superior target conformality, adequate coverage, and effective sparing of OARs. High-grade glioma (HGG) patients exhibited median PFS of 13 months (95% CI, 10.2-15.8 months) and OS of 28 months (95% CI, 23.3-32.7 months). Failure analysis revealed 58.9% in-field, 17.6% marginal, and 23.5% distant recurrences, with IDH mutation status associated with failure patterns. CONCLUSION: Preliminary findings in patients with HGG suggest a lower incidence of recurrences within the radiation field and indicate promising outcomes associated with MRIgOART. However, these observations require further validation through comparative studies.