Stereotactic Radiosurgery of Central Skull Base Meningiomas-Volumetric Evaluation and Long-Term Outcomes.

BACKGROUND AND OBJECTIVE: Complete resection of a central skull base meningioma (CSM) is possible, but it is often associated with high morbidity. Stereotactic radiosurgery (SRS) plays an appreciable role in the management of skull base meningiomas. This study aims to apply volumetric methods to assess the CSM response after SRS and correlate it with clinical outcomes.

MATERIALS AND METHODS: The cohort consisted of 219 patients, of whom 73.9% were female (n = 162), with a median age of 55 years (19-88). SRS was the primary treatment for 45.7% (n = 100), while 37.9% (n = 83) underwent treatment for residual tumors, 14.2% (n = 31) for recurrence, and in 5 with others reasons. The median tumor volume was 4.9 cm3 (0.3-105 cm3 ) to a median margin dose of 14 Gy (5-35 Gy). Volumetric analysis of CSM was performed on the SRS scan and each available magnetic resonance image thereafter.

RESULTS: The median clinical and imaging follow-ups of the cohort were 72 (24-298) and 66 (18-298) months, respectively. The overall tumor control rate was 83.4% (n = 183) at last follow-up with tumor regression 72.1% (n = 158). Neurologic symptoms were improved after SRS in 6.8% (n = 15), stable in 72.6% (n = 159), and worsened in 20.5% (n = 45). The clinical deterioration usually occurred in the patients with tumor progression (P < 0.001). Following SRS, the volumetric analysis confirmed that tumor response at 3 years reliably projected volumetric change and tumor control at 5 years (R2  = 0.694) with P < 0.001 and 10 years (R2  = 0.571) with P = 0.001.

CONCLUSION: SRS affords effective tumor volumetric control and neurologic stability or improvement in the majority of patients with CSMs. The radiologic response of CSM as determined by volumetry at 3 years post-SRS is predictive of long-term tumor response at 5 and 10 years following SRS.