Background: Gamma knife stereotactic radiosurgery (SRS) has become an important management strategy for patients with meningiomas. Although prior reports have studied early tumor control, neurological response, and associated morbidity, our purpose was to use clinical and imaging studies to determine whether long-term outcomes remain stable over time.
Materials and Methods: We studied 290 consecutive patients (92 men and 198 women) who underwent gamma knife SRS for a meningioma between 1987 and 1997. The median tumor margin dose was 15 Gy and the median tumor volume was 5.5 mL. Target definition was performed using contrast enhanced computed tomography in 72 patients and magnetic resonance imaging in 218 patients. The median patient age at radiosurgery was 61 years. Twenty patients had a history of fractionated radiation therapy, 136 patients had undergone a subtotal resection, and 22 patients had recurrences after initial gross total resection.
Results: The overall tumor control rate was 91%. Twenty-six patients (9%) had evidence of delayed local tumor growth and 44 (15%) had regional tumor progression, which occurred at a median of 38 months. The 10- and 20-year actuarial rates of freedom from tumor progression of the targeted tumor were 87.7%±2.5% and 87.2%±4.2%. Of 234 patients who had symptoms before SRS (n=62, 26%) improved, 126 (54%) had no change in symptoms and 46 (20%) gradually worsened. Thirty-two of 34 (94%) asymptomatic patients remained asymptomatic. We found no difference in long-term tumor control rates between patients who had undergone craniotomy before radiosurgery (89%) and patients who underwent primary radiosurgery (93.1%). Adverse radiation effects were detected in 3.1% of patients. Factors associated with worse progression-free survival included prior radiation therapy (P<0.0001) and higher grade meningioma (P<0.0001). At a median of 8.7 years after SRS, 137 patients were dead at a median age of 77 years.
Conclusions: We found that gamma knife SRS provided durable tumor control with low morbidity in meningioma patients.