Precision Radiotherapy for Refractory Brain Metastases: A Multicenter Study

Conventional image-guided techniques (such as cone-beam CT) have poor soft tissue contrast and unsatisfactory treatment outcomes. MRgART offers high-resolution imaging of brain tissue and, by acquiring daily MR images, successfully achieves real-time image monitoring, displaying tumor position and volume changes during treatment. This may improve local control rates for brain metastases, reduce toxicities, and translate into survival benefits. Our research team has already conducted a phase II prospective study and achieved favorable results, with a 1-year local control rate of 100% for intracranial brain metastases, significantly superior to historical controls of conventional radiotherapy, no severe late toxicities, and real-time individualized precision treatment. Based on the phase II study results, this phase III single-arm prospective study was designed. This study aims to conduct a multicenter prospective study to establish an MR-guided adaptive radiotherapy (MRgART) technical platform, enabling real-time monitoring of tumor position and volume changes and individualized plan adaptation. Through technological innovation, we aim to significantly improve local control rates for large and complexly located brain metastases while reducing severe adverse effects such as radiation brain necrosis, thereby laying the technical foundation for precise and safe treatment. This study will establish a new technical system for adaptive radiotherapy (ART) for brain metastases based on per-fraction MR images acquired during radiotherapy, using adaptive radiotherapy to improve target dose coverage and reduce radiation doses to organs at risk such as normal brain tissue. It is anticipated to validate the phase II findings of high local control, low toxicity, and significantly prolonged survival. Based on the obtained results, combined with multicenter clinical practice and application experience, domestic and international expert symposiums and special sessions will be conduct