Evaluation of particle radiotherapy for the re-irradiation of recurrent intracranial meningioma

BACKGROUND: With the advance of modern irradiation techniques, the role of radiotherapy (RT) for intracranial meningioma has increased significantly throughout the past years. Despite that tumor’s generally favorable outcome with local control rates of up to 90% after ten years, progression after RT does occur. In those cases, re-irradiation is often difficult due to the limited radiation tolerance of the surrounding tissue. The aim of this analysis is to determine the value of particle therapy with its better dose conformity and higher biological efficacy for re-irradiating recurrent intracranial meningioma. It was performed within the framework of the “clinical research group heavy ion therapy” and funded by the German Research Council (DFG, KFO 214). METHODS: Forty-two patients treated with particle RT (protons (n = 8) or carbon ions (n = 34)) for recurrent intracranial meningioma were included in this analysis. Location of the primary lesion varied, including skull base (n = 31), convexity (n = 5) and falx (n = 6). 74% of the patients were categorized high-risk according to histology with a WHO grading of II (n = 25) or III (n = 6), in the remaining cases histology was either WHO grade I (n = 10) or unknown (n = 1). Median follow-up was 49,7 months. RESULTS: In all patients, re-irradiation could be performed safely without interruptions due to side effects. No grade IV or V toxicities according to CTCAE v4.0 were observed. Particle RT offered good overall local control rates with 71% progression-free survival (PFS) after 12 months, 56,5% after 24 months and a median PFS of 34,3 months (95% CI 11,7–56,9). Histology had a significant impact on PFS yielding a median PFS of 25,7 months (95% CI 5,8–45,5) for high-risk histology (WHO grades II and III) while median PFS was not reached for low-risk tumors (WHO grade I) (p = 0,03). Median time to local progression was 15,3 months (Q1-Q3 8,08–34,6). Overall survival (OS) after re-irradiation was 89,6% after 12 months and 71,4% after 24 months with a median OS of 61,0 months (95% CI 34,2–87,7). Again, WHO grading had an effect, as median OS for low-risk patients was not reached whereas for high-risk patients it was 45,5 months (95% CI 35,6–55,3). CONCLUSION: Re-irradiation using particle therapy is an effective method for the treatment of recurrent meningiomas. Interdisciplinary decision making is necessary to guarantee best treatment for every patient.