Radiation-Induced Meningiomas: Systematic Review with Pooled Case Analysis and Case Series of Long Latency,...

Objective: Radiation-induced meningiomas (RIMs) are a rare but clinically relevant late complication of cranial irradiation, characterized by long latency and potentially aggressive behavior. This study aimed to systematically analyze the relationships between radiation dose, age at irradiation, latency period, histological grade, tumor multiplicity, and recurrence in RIMs. Methods: A systematic review and pooled case analysis of published cases of RIMs was performed, supplemented by a case series of four institutional patients. Data were extracted on primary tumor type, radiation dose, age at irradiation, latency period, World Health Organization (WHO) grade, tumor multiplicity, and recurrence. Radiation dose was categorized as low (<20 gray (Gy)), intermediate (20-40 Gy), or high (>40 Gy). Statistical analyses included χ² tests, Mann-Whitney U tests, Kruskal-Wallis tests, and Spearman correlation analyses. Results: A total of 1809 patients were included. A higher radiation dose was significantly associated with shorter latency (p < 0.001), a higher WHO grade (p < 0.001), and increased tumor multiplicity (p < 0.001). High-grade RIMs occurred predominantly after high-dose irradiation. Tumor recurrence was significantly more frequent in high-grade than low-grade meningiomas (51.5% vs. 18.3%, p < 0.001), but it was not associated with radiation dose. Older age at irradiation correlated with longer latency (Spearman's ρ = 0.405, p < 0.001). No association was observed between primary tumor category and WHO grade. Conclusions: RIMs demonstrate dose- and age-dependent biological behavior, with higher radiation doses and younger age at irradiation predisposing to earlier onset and increased aggressiveness. These findings suggest that long-term, dose-adapted radiological surveillance may warrant consideration in irradiated patients.