|In the recent study from the Mayo
Clinic, Gamma Knife results may be superior to surgery (see study.) Also
Pitt reported good results for unbiopsied meningiomas (see study.)
The radiation dose (to the margin) is 11-18Gy (with 14-15Gy as the goal.) The recent Pitt study used 14Gy and the Mayo was 17Gy. Some of the other studies cited: Taiwan (15-16Gy for < 5cc but 12-14 Gy > 10cc) Dallas (15Gy) Czech (12Gy) Japan (> 14Gy) Seattle (17Gy) Karolinska (12-15Gy)
For large tumors ( over 3cm or 13.5cc or close to optic tract by 3mm, consider using fractionated radiosurgery with the CyberKnife (go here)
Pollock. Mayo Clinic. Neurosurgery Quarterly. 2003;13(2):77-86
Lee JY,Prog Neurol Surg. 2007;20:142-9
Department of Neurological Surgery, University of Pittsburg
Between September 1987 and December 2004, 964 patients underwent Gamma Knife radiosurgery at the University of Pittsburgh for the diagnosis of meningioma. The majority of patients had tumors located at the skull base. All imaging and clinical follow-up was reviewed. Results: Overall, Gamma Knife radiosurgery provides 5- and 10-year actuarial tumor control rates of 93% for benign meningiomas. The 5-year actuarial control rate for patients with atypical and malignant meningiomas was 83 +/- 7 and 72 +/- 10%, respectively. The incidence of adverse radiation effect ranged from 5.7 to 16%; however, the incidence was gradually reduced with the advent of magnetic resonance imaging and lower dosing since 1991. Conclusion: Gamma Knife radiosurgery is an attractive option for patients with intracranial meningiomas. It can be used as both primary treatment based on imaging diagnosis alone, or as an adjunct treatment after craniotomy. It provides long-term tumor control with minimal adverse sequelae.
Long-term outcomes after meningioma radiosurgery: physician and patient perspectives.
Kondziolka D, Levy EI, Niranjan A, Flickinger JC, Lunsford LD. J Neurosurg 1999 Jul;91(1):44-50. Department of Neurological Surgery, University of Pittsburgh, Pennsylvania
The authors evaluated 99 consecutive patients who underwent radiosurgery for meningioma between 1987 and 1992. The average tumor margin dose was 16 Gy and the median tumor volume was 4.7 ml (range 0.24-24 ml). Fifty-seven patients (57%) had undergone prior resection, of which 12 procedures were considered "total." Five patients received fractionated radiation therapy before radiosurgery. Eighty-nine patients (89%) had skull base tumors. The clinical tumor control rate (no resection required) was 93%. Sixty-one (63%) of 97 tumors became smaller, 31 (32%) remained unchanged in size, and five (5%) were enlarged. Resection was performed in seven patients (7%), six of whom had undergone prior resection. New neurological deficits developed in five patients (5%) 3 to 31 months after radiosurgery. Twenty-seven (42%) of 65 responding patients were employed at the time of radiosurgery and 20 (74%) of these remained so. Radiosurgery was believed to have been "successful" by 67 of 70 patients who completed an outcomes questionnaire 5 to 10 years later. At least one complication was described by nine patients (14%) and in four patients the complications resolved. CONCLUSIONS: Five to 10 years after radiosurgery, 96% of surveyed patients believed that radiosurgery provided a satisfactory outcome for their meningioma. Overall, 93% of patients required no other tumor surgery. Incidences of morbidity in this early experience were usually transitory and relatively mild. Radiosurgery provided long-term tumor control associated with high rates of neurological function preservation and patient satisfaction.