title: Gamma Knife surgery for low-grade astrocytomas: evaluation of long-term outcome based on a 10-year experience.
abstract: OBJECTIVE
  The authors report the long-term treatment results of Gamma Knife surgery (GKS) for patients with low-grade astrocytomas who underwent surgery at a single institution.
  
  
  METHODS
  A series of 21 patients (median age 20 years) with 25 intracranial low-grade astrocytomas (World Health Organization Grades I and II) were treated with GKS between 1993 and 2003. Among them, four underwent GKS as a primary treatment. Two underwent GKS as a treatment boost after radiotherapy. In the other 15 patients, GKS was performed as an adjuvant or salvage treatment for residual/recurrent tumors after the patients had undergone craniotomy. Tumor volumes ranged from 0.2 to 13.3 ml (median 2.4 ml). Prescription margin doses ranged from 8 to 18 Gy (median 14.5 Gy). Radiation volumes were 1.3 to 21.6 ml (median 3.6 ml). Patients underwent regular follow up, with neurological evaluation and magnetic resonance imaging studies obtained at 6-month intervals. One patient was lost to follow-up. The clinical follow-up time was 5 to 144 months (median 67 months). Complete tumor remission was seen in three patients. The 10-year progression-free patient survival rate after GKS was 65%. Tumor progression was found in six patients of whom five received further salvage treatment. All the tumor progression occurred within the GKS-treated volumes. Mild-to-moderate adverse radiation effects (AREs) were found in eight patients. Both of the patients who had undergone GKS as a treatment boost after radiotherapy developed AREs, but with good shrinkage of tumors.
  
  
  CONCLUSIONS
  Gamma Knife surgery provides durable long-term local tumor control with acceptable toxicity for some patients with highly selected low-grade astrocytomas.
authors.affiliation: Cancer Center, Taipei Veterans General Hospital, Taiwan, Republic of China. lwwang@vghtpe.gov.tw
authors.forename: Ling-Wei
authors.initials: LW
authors.lastname: Wang
authors.forename: Cheng-Ying
authors.initials: CY
authors.lastname: Shiau
authors.forename: Wen-Yuh
authors.initials: WY
authors.lastname: Chung
authors.forename: Hsiu-Mei
authors.initials: HM
authors.lastname: Wu
authors.forename: Wan-Yuo
authors.initials: WY
authors.lastname: Guo
authors.forename: Kang-Du
authors.initials: KD
authors.lastname: Liu
authors.forename: Donald Ming-Tak
authors.initials: DM
authors.lastname: Ho
authors.forename: Tai-Tong
authors.initials: TT
authors.lastname: Wong
authors.forename: David Hung-Chi
authors.initials: DH
authors.lastname: Pan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001254:Astrocytoma / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D001932:Brain Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D002648:Child; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult