Reirradiation of recurrent brain tumors: a review by the ESTRO CNS Focus Group.

Purpose: Reirradiation has become an area of increasing clinical and scientific interest, particularly in neuro-oncology. This non-systematic review on central nervous system (CNS) tumors by the CNS focus group of the European Society for Radiotherapy and Oncology provides a pragmatic synthesis of the available evidence, excluding gliomas. We address key questions related to patient selection, fractionation, technical considerations, and treatment safety. Methods: Relevant studies on the use of reirradiation for meningiomas, ependymomas, brain metastases, and pituitary neuroendocrine tumors, as well as on the management of radiation necrosis, have been reviewed and summarized. Results: Reirradiation has been used with varying success in primary and secondary brain tumors. The appropriate use of reirradiation requires consideration of numerous factors, including, but not limited to, prior treatment courses, fractionation, dose to organs at risk, imaging findings, the volume of the recurrent tumor, and the interval since prior treatments. The vast majority of available studies are limited by their retrospective design, lack of standardization in reporting, and overall heterogeneity across cohorts and treatments. Conclusion: Several reirradiation studies across different tumor entities suggest potential efficacy and safety in carefully selected patients. However, important limitations remain, underscoring the need for well-designed prospective studies with rigorous reporting in both primary and secondary brain tumors.