Radiotherapy Strategies for WHO Grade 1 Meningioma: A Systematic Review and Meta-Analysis Comparing Proton Therapy, Conventional Radiotherapy, and Radiosurgery

Background/Objectives: The optimal radiotherapy modality for World Health Organization (WHO) Grade 1 meningioma remains uncertain. Proton therapy offers dosimetric advantages through reduced radiation exposure to normal brain tissue, but comparative clinical data across contemporary radiotherapy modalities are limited. We performed a systematic review and meta-analysis comparing local control (LC) outcomes among conventionally fractionated proton therapy (CF-PT), conventionally fractionated photon radiotherapy (CF-Photon RT), Linac-based stereotactic radiosurgery/radiotherapy (Linac-based SRS/SRT), and Gamma Knife radiosurgery (GKRS). Methods: A systematic literature search of PubMed (2000–2024) was conducted to identify studies reporting LC for WHO Grade 1 meningioma treated with CF-PT, CF-Photon RT, Linac-based SRS/SRT, or GKRS. Random-effects meta-analyses were performed to estimate pooled 1- to 5-year LC rates. Random-effects meta-regression analyses were conducted using modality, age, sex, and gross tumor volume (GTV) as covariates. Results: Twenty-four studies comprising 4673 patients were included in the meta-analysis. Median GTVs were larger in the CF-PT and CF-Photon RT cohorts than in the Linac-based SRS/SRT and GKRS cohorts. All modalities achieved excellent LC: 5-year LC rates were 95.9% for CF-PT, 93.0% for CF-Photon RT, 95.3% for Linac-based SRS/SRT, and 89.8% for GKRS. Meta-regression showed no significant association between modality or GTV and LC. In the CF-PT cohort, 5-year overall survival was 93.1%. Conclusions: Major radiotherapy modalities achieved excellent and comparable LC. Notably, CF-PT and CF-Photon RT maintained favorable LC despite being used for larger tumors than stereotactic approaches. Future studies are needed to evaluate long-term tumor control and treatment-related toxicity to define optimal treatment strategies.