title: Radiation-induced necrosis deteriorating neurological symptoms and mimicking progression of brain metastasis after stereotactic-guided radiotherapy.
abstract: OBJECTIVE
  Although radiation-induced necrosis (RIN) is not a tumor in itself, the lesion progressively enlarges with mass effects and diffuse peritumoral edema in a way that resembles neoplasm. To identify the RIN that mimics progression of brain metastasis, we performed surgical resections of symptomatic RIN lesions.
  
  
  METHODS
  From June 2003 to December 2005, 7 patients received stereotactic-guided radiotherapy (SRT) for metastatic brain tumor, and they later underwent craniotomy and tumor resection due to the progressive mass effects and the peritumoral edema that caused focal neurological deficit. On MR imaging, a ring-like enhanced single lesion with massive peritumoral edema could not be distinguished from progression of brain metastasis.
  
  
  RESULTS
  Four patients had non-small cell lung cancer, 2 patients had colorectal cancer and 1 patient had renal cell carcinoma. The mean tumor volume was 8.7 ml (range: 3.0 approximately 20.7 ml). The prescribed dose of SRT was 30 Gy with 4 fractions for one patient, 18 Gy for two patients and 20 Gy for the other four patients. The four patients who received SRT with a dose of 20 Gy had RIN with or without microscopic residual tumor cells.
  
  
  CONCLUSIONS
  Early detection of recurrent disease after radiotherapy and identifying radiation-induced tissue damage are important for delivering adequate treatment. Therefore, specific diagnostic tools that can distinguish RIN from progression of metastatic brain tumor need to be developed.
authors.affiliation: Neuro-Oncology Clinic, Research Institute and Hospital, National Cancer Center, Goyang, Korea.
authors.forename: Young Zoon
authors.initials: YZ
authors.lastname: Kim
authors.forename: Dae Yong
authors.initials: DY
authors.lastname: Kim
authors.forename: Heon
authors.initials: H
authors.lastname: Yoo
authors.forename: Hee Seok
authors.initials: HS
authors.lastname: Yang
authors.forename: Sang Hoon
authors.initials: SH
authors.lastname: Shin
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Hong
authors.forename: Kwan Ho
authors.initials: KH
authors.lastname: Cho
authors.forename: Seung Hoon
authors.initials: SH
authors.lastname: Lee