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The UNITED trial was a single-center phase 2 study testing MRI-guided adaptive radiotherapy for high-grade glioma using a 1.5T MR-Linac. Ninety-eight patients received standard chemoradiation, but with weekly MRI scans used to adjust radiation plans in real time. This allowed doctors to tighten treatment margins around the tumor while still accounting for microscopic spread.
The key concern with this approach had always been whether smaller margins would lead to more “missed” tumor at the edges. In this study, that did not happen. The rate of marginal failure was low (4%), meeting the study’s non-inferiority goal compared with historical outcomes. Treatment was generally well tolerated, with lymphopenia as the most common significant side effect. Overall, these results provide reassuring evidence that MRI-guided adaptive radiotherapy can safely reduce radiation margins in glioma, and support further testing in randomized trials.