title: Multiple gamma knife radiosurgery for multiple metachronous brain metastases associated with lung cancer : survival time.
abstract: OBJECTIVE
  We compared the survival time between patients with multiple gamma knife radiosurgery (GKRS) and patients with a single GKRS plus whole brain radiation therapy (WBRT), in patients with multiple metachronous brain metastases from lung cancer.
  
  
  METHODS
  From May 2006 to July 2010, we analyzed 31 patients out of 112 patients who showed multiple metachronous brain metastases. 20 out of 31 patients underwent multiple GKRS (group A) and 11 patients underwent a single GKRS plus WBRT (group B). We compared the survival time between group A and B. Kaplan-Meier method and Cox proportional hazards were used to analyze relationship between survival and 1) the number of lesions in each patient, 2) the average volume of lesions in each patient, 3) the number of repeated GKRS, and 4) the interval of development of new lesions, respectively.
  
  
  RESULTS
  Median survival time was 18 months (range 6-50 months) in group A and 6 months (range 3-18 months) in group B. Only the average volume of individual lesion (over 10 cc) was negatively related with survival time according to Kaplan-Meier method. Cox-proportional hazard ratio of each variable was 1.1559 for the number of lesions, 1.0005 for the average volume of lesions, 0.0894 for the numbers of repeated GKRS, and 0.5970 for the interval of development of new lesions.
  
  
  CONCLUSIONS
  This study showed extended survival time in group A compared with group B. Our result supports that multiple GKRS is of value in extending the survival time in patients with multiple metachronous brain metastases, and that the number of the lesions and the frequency of development of new lesions are not an obstacle in treating patients with GKRS.
authors.affiliation: Department of Neurosurgery, Research Institute of Clinical Medicine, Chonbuk National University Hospital-Chonbuk National University School of Medicine, Jeonju, Korea.
authors.forename: Hyung-Seok
authors.initials: HS
authors.lastname: Kim
authors.forename: Eun-Jeong
authors.initials: EJ
authors.lastname: Koh
authors.forename: Ha-Young
authors.initials: HY
authors.lastname: Choi
keywords: Gamma knife radiosurgery; Lung cancer; Metastases; Survival time; Whole brain radiation therapy