Re-irradiation for recurrent intracranial meningiomas: Analysis of clinical outcomes and prognostic factors

•Re-irradiation (re-RT) of intracranial recurrent meningiomas is still matter of debate and limited by radiation tolerance of the surrounding tissue and the increased risk of side effects.•Re-RT is increasingly considered in current clinical practice, but its efficacy and safety for brain tumors are still under investigation. The optimal choice of patient selection, RT modalities and dose for re-irradiation are not well established yet.•This retrospective analysis aims at providing data about clinical outcomes, toxicities and prognostic factors in a cohort of 181 intracranial recurrent meningioma patients treated in 8 different Italian centers with different RT modalities. Re-irradiation (re-RT) for recurrent intracranial meningiomas is hindered by the limited radiation tolerance of surrounding tissue and the risk of side effects. This study aimed at assessing outcomes, toxicities and prognostic factors in a cohort of patients with recurrent meningiomas re-treated with different RT modalities. A multi-institutional database from 8 Italian centers including intracranial recurrent meningioma (RM) patients who underwent re-RT with different modalities (SRS, SRT, PT, EBRT) was collected. Biologically Equivalent Dose in 2 Gy-fractions (EQD2) and Biological Effective Dose (BED) for normal tissue and tumor were estimated for each RT course (α/β = 2 for brain tissue and α/β = 4 for meningioma). Primary outcome was second progression-free survival (s-PFS). Secondary outcomes were overall survival (OS) and treatment-related toxicity. Kaplan–Meier curves and Cox regression models were used for analysis. Between 2003 and 2021 181 patients (pts) were included. Median age at re-irradiation was 62 (range 20–89) and median Karnofsky Performance Status (KPS) was 90 (range 60–100). 78 pts were identified with WHO grade 1 disease, 65 pts had grade 2 disease and 10 pts had grade 3 disease. 28 pts who had no histologic sampling were grouped with grade 1 patients for further analysis. Seventy-five (41.4 %) patients received SRS, 63 (34.8 %) patients SRT, 31 (17.1 %) PT and 12 (6.7 %) EBRT. With a median follow-up of 4.6 years (interquartile range 1.7–6.8), 3-year s-PFS was 51.6 % and 3-year OS 72.5 %. At univariate analysis, SRT (HR 0.32, 95 % CI 0.19–0.55, p 5