title: Smoking and survival of breast cancer patients: A meta-analysis of cohort studies.
abstract: OBJECTIVE
  Published articles reported controversial results about the association of breast cancer survival with smoking. Hence, a meta-analysis was performed to investigate this association.
  
  
  METHODS
  A comprehensive search was performed to identify relevant cohort studies (up to May 31st, 2016). In the current smoking and former smoking v. never smoking analyses, the fixed- or random-effect model was selected based on the heterogeneity test among studies. And the heterogeneity was measured using Q test and I2statistic. Publication bias was estimated using Egger's regression asymmetry test.
  
  
  RESULTS
  Thirteen articles with 44 studies were included. Compared with never smokers, current smokers have a higher breast cancer-specific mortality and all-cause mortality, with pooled hazard ratio (HR) (HR = 1.30 95%CI: 1.16-1.45; I2= 52.4%) and (HR = 1.59, 95%CI: 1.41-1.78; I2= 87.1%), respectively. While former smokers tend to have a moderately increased all-cause mortality (HR = 1.10, 95%CI: 1.07-1.12; I2= 0.0%), but there was no significant association between former smoking and breast cancer-specific mortality (HR = 0.95, 95%CI: 0.90-1.02; I2= 0.0%).
  
  
  CONCLUSIONS
  The present evidence indicates that current smoking leads to higher breast cancer-specific mortality and all-cause mortality than never smoking in breast cancer patients. However former smoking just causes a mild increase in all-cause morality, but not breast cancer-specific mortality.
authors.affiliation: Department of Epidemiology and Biostatistics, Shandong University, Jinan 250012, Shandong, PR China.
authors.forename: Wenhou
authors.initials: W
authors.lastname: Duan
authors.affiliation: Department of Epidemiology and Biostatistics, Shandong University, Jinan 250012, Shandong, PR China.
authors.forename: Suyun
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Epidemiology and Biostatistics, Shandong University, Jinan 250012, Shandong, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Meng
authors.affiliation: Department of Epidemiology and Biostatistics, Shandong University, Jinan 250012, Shandong, PR China.
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Epidemiology and Biostatistics, Shandong University, Jinan 250012, Shandong, PR China. Electronic address: jiachongqi@sdu.edu.cn.
authors.forename: Chongqi
authors.initials: C
authors.lastname: Jia
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000401:mortality*; D002423:Cause of Death; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking / Q000401:mortality*; D055815:Young Adult
keywords: Breast cancer; Meta-analysis; Smoking; Survival