Progressive intracranial meningioma regression after standalone endovascular embolization: a multicenter study

BACKGROUND: Endovascular embolization of intracranial meningiomas has traditionally served as a preoperative adjunct but has been sporadically described as a standalone treatment. We present the largest multicenter cohort evaluating standalone embolization for intracranial meningiomas. METHODS: We retrospectively analyzed 41 meningiomas in 40 patients treated with standalone embolization across four centers. Radiographic response was assessed using serial volumetric MRI over 12 months. Enhancing tumor volume (ETV) and total tumor volume (TTV) were analyzed longitudinally using mixed-effects models. An early devascularization index (EDI), derived from 24-72-hour postprocedural ETV, was tested as a predictor of subsequent tumor response. The primary clinical endpoint was the modified Rankin Scale (mRS). RESULTS: Mean age was 62.2±13.7 years (82.5% female). Median TTV reduction was 28.6% at 1 month, 57.1% at 6 months, and 81.7% at 12 months (all p≤0.002), with a significant overall time effect (p<0.001). ETV decreased a median of 83.1% within 24-72 hours (p=0.002), consistent with early devascularization, and EDI was positively associated with greater subsequent shrinkage (pooled p=0.002). Neither baseline edema nor tumor location modified the response. mRS was stable or improved in 39 of 40 patients. Complications occurred in 4 of 41 lesions (9.8%), with only one resulting in clinical decrement in mRS from 0 to 1. No patient required subsequent surgery or radiotherapy. CONCLUSIONS: Standalone embolization was successfully used as a standalone treatment, inducing significant progressive tumor regression as early as 1 month and sustained at 12 months. Prospective studies are warranted.