title: A systematic review of risk factors for brain metastases and value of prophylactic cranial irradiation in non-small cell lung cancer.
abstract: BACKGROUND
  The incidence of brain metastases (BM) varies in patients with non-small cell lung cancer (NSCLC), calls into question the value of prophylactic cranial irradiation (PCI). It is possible that clinicopathologic characteristics are associated with the development of BM, but these have yet to be identified in detail. Thus, we conducted the present meta-analysis on risk factors for BM and the value of PCI in patients with NSCLC.
  
  
  METHODS
  Eligible data were extracted and the risk factors for BM and the value of PCI in patients with NSCLC were analyzed by calculating the pooled odds ratio (OR). Heterogeneity was detected using Q and I-squared statistics, and publication bias was tested by funnel plots and Egger's test.
  
  
  RESULTS
  Six randomized controlled trials with a focus on the value of PCI and 13 eligible studies with a focus on risk factors for BM were included. PCI significantly reduced the incidence of BM in patients with NSCLC (p=0.000, pooled OR=0.34, 95% confidence interval = 0.37-0.59). Compared with non-squamous cell carcinoma, squamous cell carcinoma was associated with a low incidence of BM in patients with NSCLC (p=0.000, pooled OR=0.47, 95% confidence interval =0.34- 0.65). The funnel plot and Egger's test suggested that there was no publication bias in the current meta-analysis.
  
  
  CONCLUSIONS
  This meta-analysis provides statistical evidence that compared with non-squamous cell carcinoma, squamous cell carcinoma can be used as a predictor for BM in patients with NSCLC, and PCI might reduce the incidence of BM in patients with NSCLC, but does not provide a survival benefit.
authors.affiliation: Cancer Center, the Second Hospital of Shandong University, Jinan, China E-mail : sdshsduniversity@163.com.
authors.forename: Dian-Shui
authors.initials: DS
authors.lastname: Sun
authors.forename: Li-Kuan
authors.initials: LK
authors.lastname: Hu
authors.forename: Ying
authors.initials: Y
authors.lastname: Cai
authors.forename: Xiao-Mei
authors.initials: XM
authors.lastname: Li
authors.forename: Lan
authors.initials: L
authors.lastname: Ye
authors.forename: Hua-Ying
authors.initials: HY
authors.lastname: Hou
authors.forename: Cui-Hong
authors.initials: CH
authors.lastname: Wang
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Jiang
mesh_terms: D001932:Brain Neoplasms / Q000453:epidemiology / Q000517:prevention & control* / Q000532:radiotherapy / Q000556:secondary*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000473:pathology; D016371:Cranial Irradiation; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology; D012307:Risk Factors