title: Radiation-induced intratumoral necrosis and peritumoral edema after gamma knife radiosurgery for intracranial meningiomas.
abstract: OBJECTIVE
  To study the clinical significance and relevant factors of radiation-induced intratumoral necrosis (RIN) and peritumoral edema (PTE) after Gamma knife radiosurgery (GKRS) for intracranial meningiomas.
  
  
  METHODS
  We retrospectively analyzed the data of 64 patients who underwent GKRS for intracranial meningioma. The mean lesion volume was 4.9 cc (range, 0.3-20), and the mean prescription dose of 13.4 Gy (range, 11-18) was delivered to the mean 49.9% (range, 45-50) isodose line. RIN was defined as newly developed or enlarged intratumoral necrosis after GKRS.
  
  
  RESULTS
  RIN and new development or aggravation of PTE were observed in 21 (32.8%) and 18 (28.1%) cases of meningioma, respectively during the median follow-up duration of 19.9±1.0 months. Among various factors, maximum dose (>25 Gy) and target volume (>4.5 cc) were significantly related to RIN, and RIN and maximum dose (>24 Gy) were significantly related to the development or aggravation of PTE. In 21 meningiomas with development of RIN after GKRS, there was no significant change of the tumor volume itself between the times of GKRS and RIN. However, the PTE volume increased significantly compared to that at the time of GKRS (p=0.013). The median interval to RIN after GKRS was 6.5±0.4 months and the median interval to new or aggravated PTE was 7.0±0.7 months.
  
  
  CONCLUSIONS
  A close observation is required for meningiomas treated with a maximum dose >24 Gy and showing RIN after GKRS, since following or accompanying PTE may deteriorate neurological conditions especially when the location involves adjacent critical structures.
authors.affiliation: Department of Neurosurgery, Ajou University School of Medicine, Suwon, Korea. ; Department of Physics, Yeungnam University, Gyeongsan, Korea.
authors.forename: Sang Ryul
authors.initials: SR
authors.lastname: Lee
authors.forename: Kyung Ah
authors.initials: KA
authors.lastname: Yang
authors.forename: Sung Kyu
authors.initials: SK
authors.lastname: Kim
authors.forename: Se-Hyuk
authors.initials: SH
authors.lastname: Kim
keywords: Gamma knife radiosurgery; Intracranial meningioma; Peritumoral edema; Radiation necrosis