Radiotherapy represents an effective treatment approach during therapy for a meningeoma, a brain tumor that arises from the minenges membrane layers. This therapy is particularly preferred in the case of inoperable patients. In the case of hard-to-reach tumors, biopsies are frequently avoided due to the potential risks posed by an operation: the lack of tumor material removes the possibility of a radiation treatment planning adapted to the tumor’s aggressiveness. The project aims to establish so-called exosomes, molecules circulating freely in the bloodstream, as potential biomarkers in the sense of a liquid biopsy for marking the response to therapy and toward the early detection of relapses. The molecular profile of the exosomes will be additionally studied. This is intended to enable a conclusion to be drawn regarding the tumor biology and aggressiveness of the meningeoma. These factors can then be taken into consideration within therapeutic management (e.g. aftercare intervals).