Recurrence pattern analysis after [68Ga]-DOTATATE-PET/CT-planned radiotherapy of high-grade meningiomas

Background: The aim of the present study was to evaluate the influence of the applied safety margins of modern intensity-modulated radiotherapy (IMRT) in patients with high-grade meningiomas on local control and recurrence patterns. Methods: Twenty patients with a neuropathological diagnosis of a high-grade meningioma (WHO degrees II or degrees III) treated with adjuvant or definitive radiotherapy between 2010 and 2015 were included in the present retrospective analysis. All patients were planned PET-based. Recurrence patterns were assessed by means of MRI and/or DOTATATE-PET/computertomography (CT). Results: The median follow-up was 31.0 months [95% confidence interval (CI): 20.1-42.0] and the progressionfree survival (PFS) after 24 months was 87.5%. Overall, four patients had a local recurrence of their meningioma. Of these, three were located in field according to the prior radiotherapy treatment region, while only one patient had a distant relapse. There were no independent factors influencing progression-free or overall survival (OS). Conclusion: After radiotherapy (RT), patients with atypical or anaplastic meningiomas still have a defined risk of tumor recurrence. The aim of the present study was to examine mono-institutional data concerning target volume definition and recurrence patterns after radiotherapy of high-grade meningiomas as there are limited data available. Our data suggest that extended safety margins are necessary to achieve a favorable local control for high-grade meningiomas.