Radiation-induced intratumoral necrosis and peritumoral edema after Gamma knife radiosurgery for intracranial meningiomas

Lee SangRyul1, KyungAh Yang2, SeHyuk Kim2

1Suwon, Korea, Republic Of 2Department of Neurosurgery, Ajou University Hospital, Suwon, Korea

Keywords: meningioma, gamma knife, complications, radiation injury, outcome

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     . Meningioma radiosurgery can be associated with complications and radiation injury.
     Our purpose was to study the incidence and clinical significance of radiation-induced intratumoral necrosis (RIN) and peritumoral edema after Gamma knife radiosurgery (GKRS) for intracranial meningiomas, and to investigate relevant factors
     We retrospectively analyzed the data of sixty-seven patients with 74 intracranial meningiomas who underwent GKRS between August 2008 and January 2011. The mean age at the time of GKRS was 59.6 years (range, 29-90). The mean lesion volume was 4.6 cc (range, 0.3-20), and the mean prescription dose of 13.2 Gy (range, 11-18) was delivered to the mean 50.6 % (range, 45-70) isodose line.
      RIN was defined as newly developed intratumoral necrosis or enlargement of pre-existing necrosis after GKRS.
     RIN occurred in 22 (29.7 %) of 74 lesions during the median follow-up duration of 19.9 ± 1.0 months (range, 3.7–35.1). The median interval to RIN was 6.5 ± 0.4 months (range, 3.7–17.0). Among the 22 lesions, peritumoral edema was present in 8 (36.4%) at the time of GKRS. There was no significant change of tumor volume itself between the time of GKRS and RIN (mean; 7.0 vs. 7.8 cc). However, 14 (63.6 %) lesions showed peritumoral edema at the time of RIN and the peritumoral edema volume increased significantly (p=0.013, Wilcoxon signed ranks test). Ten out of 22 lesions were symptomatic and decompressive surgery was required in 1 patient because of severe peritumoral edema. Target volume >4.5 cc (p=0.002) was a significant factor related to RIN, and development of RIN (p=0.001) and maximum dose >24 Gy (p=0.017) were significantly related to development or aggravation of peritumoral edema.
     This was a retrospective review.
     According to our results, we suggest that close observation is required for meningiomas of >4.5 cc showing RIN after GKRS .
     Larger volumes can be associated with accompanying peritumoral edema which may worsen the  neurological condition when they are located adjacent to critical structures or the cerebrospinal fluid pathway


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L. SangRyul (), K. Yang (), S. Kim ()