Meningioma metastases: incidence and proposed screening paradigm.

OBJECTIVE: Extracranial meningioma metastases are uncommon, occurring in less than 1% of patients diagnosed with meningioma. Due to the rarity of meningioma metastases, patients are not routinely screened for distant disease. In this series, we report their experience with meningioma metastases and results of screening for metastases in select patients with recurrent meningiomas. METHODS: All patients undergoing resection or stereotactic radiosurgery for primary or recurrent meningioma from 2009 to 2017 at a single center were retrospectively reviewed to identify patients who were diagnosed with or underwent imaging to evaluate for systemic metastases. Imaging to evaluate for metastases was performed with CT scanning of the chest, abdomen, and pelvis or whole-body PET/CT using either FDG or 68Ga-DOTA-octreotate (DOTATATE) tracers in 28 patients. Indications for imaging were symptomatic lesions concerning for metastasis or asymptomatic screening in patients with greater than 2 recurrences being evaluated for additional treatment. RESULTS: Of 1193 patients treated for meningioma, 922 (77.3%) patients had confirmed or presumed WHO grade I tumors, 236 (19.8%) had grade II tumors, and 35 (2.9%) had grade III tumors. Mean follow-up was 4.3 years. A total of 207 patients experienced recurrences (17.4%), with a mean of 1.8 recurrences. Imaging for metastases was performed in 28 patients; 1 metastasis was grade I (3.6%), 16 were grade II (57.1%), and 11 were grade III (39.3%). Five patients (17.9%) underwent imaging because of symptomatic lesions. Of the 28 patients screened, 27 patients had prior recurrent meningioma (96.4%), with a median of 3 recurrences. On imaging, 10 patients had extracranial lesions suspicious for metastasis (35.7%). At biopsy, 8 were meningioma metastases, 1 was a nonmeningioma malignancy, and 1 patient was lost to follow-up prior to biopsy. Biopsy-confirmed metastases occurred in the liver (5), lung (3), mediastinum (1), and bone (1). The observed incidence of metastases was 0.67% (n = 8). Incidence increased to 2% of WHO grade II and 8.6% of grade III meningiomas. Using the proposed indications for screening, the number needed to screen to identify one patient with biopsy-confirmed malignancy was 3.83. CONCLUSIONS: Systemic imaging of patients with multiply recurrent meningioma or symptoms concerning for metastasis may identify extracranial metastases in a significant proportion of patients and can inform decision making for additional treatments.