Radiosurgery of benign intracranial meningiomas: factors associated with successful treatment

Scott Stafford1, Michael Link1, Yolanda Garces2, Robert Foote2, Bruce Pollock2

1Rochester, United States 2Mayo Clinic Rochester, Rochester, USA

Keywords: meningioma, outcome, gamma knife, radiosurgery, skull base

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     Radiosurgery of benign intracranial meningiomas is an accepted management option. 
     Proper patient selection is essential to ensure good patient outcomes.
     The majority of tumors (n=337, 81%) involved the skull base/tentorium. The mean tumor volume was 9.2 cm3 (range, 0.3-48.6); the mean tumor margin dose was 15.9Gy (range, 12-20). The mean follow-up was 74 months (range, 6-234).
     Restrospective analysis of the prospectively acquired Mayo Gamma Knife data base of 417 patients (305 women/112 men) having single-fraction SRS for imaging defined (n=251) or confirmed WHO Grade I (n=166) meningiomas from 1990-2008, using the Leksell Gamma Unit. Excluded were patients with radiation-induced tumors, meningiomatosis, or Neurofibromatosis.  
     Tumor growth of the irradiated tumor was noted in 11 patients (2.6%) and adjacent to the irradiated tumor (marginal failure) in 13 patients (3.1%). The 5-year and 10-year actuarial local control (LC) rate was 96% and 89%, respectively. Prior tumor resection was associated with a higher treatment failure rate (HR=8.3, 95% CI 2.5-27.8, P<0.001). The 1-year and 5-year actuarial complication rate was 6% and 11%, respectively. Increasing tumor volume (HR=1.06, 95% CI 1.03-1.09, P<0.001) and tumors of the falx/convexity (HR=3.0, 95% CI 1.6-5.6, P=0.004) were associated with permanent treatment-related complications. A grading system was tested based on three factors tumor location (skull base/tentorium=0, falx/convexity=1) + prior resection (no=0, yes=1) + tumor volume (<4.0 cm3=1, 4.0-10.0 cm3=2, >10.0 cm3=3), yielding a score from 1-5. The percentage of patients with LC without treatment-related complications correlated with the calculated meningioma score: 1 point (n=70, 94%), 2 points (n=120, 92%), 3 points (n=116, 85%), 4 points (n=94, 76%), 5 points (n=17, 35%).
     This was a retrospective study.
     Single-fraction SRS at the studied dose range provided a high rate of tumor control for patients with benign intracranial meningiomas.  
     Patients with small volume, un-operated skull base or tentorial meningiomas had the best outcomes after single-fraction SRS.


Project Roles:

S. Stafford (), M. Link (), Y. Garces (), R. Foote (), B. Pollock ()