The advantages of Gamma Knife radiosurgery compared with other treatments for conditions in the brain, head and neck .
Michael Torrens MPhil ChM FRCS
Director, Gamma Knife Department
Hygeia Hospital, Athens
Gamma Knife radiosurgery  is the ablation of a chosen target by a (usually) single large dose of focused photon radiation. The mechanical accuracy of this treatment is <0.3mm.
EQUALLY EFFECTIVE AS SURGERY: Total control by radiosurgery is achieved in over 92% of most benign conditions .
NON-INVASIVE: The ability to effectively treat these conditions with similar surgical precision and results through the intact skull eliminates many of the risks and discomfort of open surgery and general anesthesia. Gamma Knife radiosurgery requires no incisions, is performed under local anesthesia and is performed with minimal discomfort.
FEWER COMPLICATIONS: Radiosurgery has fewer complications and a better outcome than surgery  and is particularly useful in patients with co-existent illnesses where conventional surgery would pose an unacceptable risk. It also causes fewer cognitive changes than radiotherapy .
MORE COST EFFECTIVE: As a one-day outpatient procedure, the cost effectiveness of Gamma Knife treatment usually exceeds that of open surgery and radiotherapy [5,6].
CAN BE USED AFTER OTHER TREATMENTS FAIL: Recurrence after surgery, radiotherapy and drug treatment is not a contraindication to Gamma Knife treatment.
MORE ACCURATE: The mechanical accuracy is up to ten times more accurate than linear accelerator based radiosurgery [7,8].
PATIENT ACCEPTABILITY: The safety, simplicity and improved quality of life make Gamma knife treatment the preferred choice of informed patients. Hospitalization is only required in exceptional circumstances and most patients are able to return to their normal activities within 24 hours of the procedure.
For all these reasons the method is recommended after appropriate review by multidisciplinary teams (MDT) by entities such as the UK National Health service .
WHO CAN BENEFIT FROM THIS TREATMENT?
The technique, indications and results have been reviewed  but include:
Benign brain tumors such as meningiomas, acoustic neuromas, pituitary adenomas and craniopharyngiomas
Brain metastases such as from melanoma or lung, breast, colon or kidney cancer
Head and neck tumors such as nasopharyngeal carcinomas and ocular melanomas
Primary or recurrent malignant brain tumors such as astrocytomas, oligodendrogliomas, glioblastoma multiforme and ependymomas
Lesions that are causing intracranial hypertension or serious symptoms of pressure on the brain.
Lesions larger than about 4cm diameter or volume 20cc.
Multiple lesions such as metastases if more than 10-15, depending on volume.
Lesions where the diagnosis is not well substantiated or other, better treatment exists.
The incidence of primary intracranial tumours is 50 per million in the UK  and the incidence of secondary metastatic tumours is much higher at perhaps 450 per million . AVM incidence is 10 per million and prevalence of trigeminal neuralgia 155 per million .
If Gamma Knife radiosurgery were to be appropriate for only 20% of such cases (and it is likely to be more frequently useful) then a machine would be necessary for every 5 million population, because each machine can treat 2-3 cases per working day.
Pellet W, Regis J, Roche PH, Delsanti C. Relative indications for radiosurgery and microsurgery for acoustic schwannoma. Adv Tech Stand Neurosurg. 2003;28:227-82.
Noudel R, Gomis P, Duntze J, Marnet D, Bazin A, Roche PH. Hearing preservation and facial nerve function after microsurgery for intracanalicular vestibular schwannomas: comparison of middle fossa and retrosigmoid approaches. Acta Neurochir (Wien). 2009;151(8):935-44.
Chang EL, Wefel JS, Hess KR, Allen PK, Lang FF, Kornguth DG, Arbuckle RB, Swint JM, Shiu AS, Maor MH, Meyers CA. Neurocognition in patients with brain metastases treated with radiosurgery or radiosurgery plus whole-brain irradiation: a randomised controlled trial. Lancet Oncol. 2009;10(11):1037-44.
Rutigliano MJ,Lunsford LD, Kondziolka D, Strauss M, Khanna V, Green M. The Cost Effectiveness of Stereotactic Radiosurgery versus Surgical Resection in the Treatment of Solitary Metastatic Brain Tumors. Neurosurgery 1995; 37(3): 445–455
Lee WY, Cho DY, Lee HC, Chuang HC, Chen CC, Liu JL, Yang SN, Liang JA, Ho LH. Outcomes and cost-effectiveness of gamma knife radiosurgery and whole brain radiotherapy for multiple metastatic brain tumors. J Clin Neurosci. 2009;16(5):630-4.
Heck B, Jess-Hempen A, Kreiner HJ, Schöpgens H, Mack A. Accuracy and stability of positioning in radiosurgery: long-term results of the Gamma Knife system. Med Phys. 2007 Apr;34(4):1487-95.