Abstract
Objective: Single fraction radiosurgery has been a well known, safe and effective treatment option for patients with small meningiomas. In case of relatively large tumors, fractionated frameless radiosurgery can be utilised to reduce the dose of radiation to organ at risk and thus preventing development of peritumoral edema. The aim of this retrospective analysis is to present our initial institutional experience of hypofractionated frameless radiosurgery with Gamma Knife Icon in terms of safety and short-term efficacy for the treatment of primary or recurrent meningiomas.
METHODS: This cohort consists 97 patients with intracranial benign meningiomas who underwent fractionated GKRS between May 2017 and April 2019 at the Koc University Hospital Gamma Knife Center. The median age was 52.5 years (range 13-83 years), and 78.2% of the patients were women. None of the patient had undergone prior radiotherapy All patients tolerated mask system without any complaints or complications.
The median tumor volume was 10,9 cm3 (range 0.2-34.0 cm3) for the whole group and 36 (37.5%) patients received 3-fraction treatment. For this patient cohort, the mean tumor volume was 7.5 cm3 and a median margin dose of 6 Gy/fraction (range 5.5-7 Gy) was delivered to the tumor with a median isodose line of 45% (range 40%-50%). For patients who received 5-fraction treatment, the mean tumor volume was 13,7 cm3 and a median margin dose of 4.5 Gy/fraction (range 4-5 Gy) was prescribed with a median isodose line of 45% (range 40%-55%). All patients tolerated mask system without any complaints or complications. All patients received 2 mg of oral dexamethasone during the treatment days.
RESULTS: Follow-up data was available for 75 patients. During a median follow-up of 9.5 months (range 6-20 months), tumor volume remained stable for all patients. Of the 75 patients, 6 presented with additional neurological symptoms or signs (trigeminal neuralgia (one), new-onset epileptic seizures (three) and worsening of gait ataxia (two)). Four of this six patients received additional oral dexamethasone for peritumoral edema.
CONCLUSIONS: Fractionated frameless stereotactic radiosurgery with Gamma Knife Icon provided good short term local tumor control and high preservation of neurological function in patients with intracranial meningiomas. Further studies with larger sample sizes and longer follow-up duration are warranted.
