title: Prognostic impact of body mass index stratified by smoking status in patients with esophageal squamous cell carcinoma.
abstract: BACKGROUND
  As smoking affects the body mass index (BMI) and causes the risk of esophageal squamous cell carcinoma (ESCC), the prognostic impact of BMI in ESCC could be stratified by smoking status. We investigated the true prognostic effect of BMI and its potential modification by smoking status in ESCC.
  
  
  METHODS
  We retrospectively analyzed 459 patients who underwent curative treatment at a single institution between January 2007 and December 2010. BMI was calculated using the measured height and weight before surgery. Chi-square test was used to evaluate the relationships between smoking status and other clinicopathological variables. The Cox proportional hazard models were used for univariate and multivariate analyses of variables related to overall survival.
  
  
  RESULTS
  BMI <18.5 kg/m2was a significantly independent predictor of poor survival in the overall population and never smokers after adjusting for covariates, but not in ever smokers. Among never smokers, underweight patients (BMI <18.5 kg/m2) had a 2.218 times greater risk of mortality than non-underweight (BMI ≥18.5 kg/m2) patients (P=0.015). Among ever smokers, BMI <18 kg/m2increased the risk of mortality to 1.656 (P=0.019), compared to those having BMI ≥18 kg/m2.
  
  
  CONCLUSIONS
  Our study is likely the first to show that the prognostic effect of BMI was substantial in ESCC, even after stratifying by smoking status. Furthermore, the risk of death due to low BMI would be significantly increased in never smokers. We believe that the prognostic impact of BMI is modified but not eliminated by the smoking status in ESCC.
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Peng
authors: P
authors: Sun
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Fei
authors: F
authors: Zhang
authors: Department of Oncology, the First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, People's Republic of China.
authors: Cui
authors: C
authors: Chen
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Chao
authors: C
authors: Ren
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Xi-Wen
authors: XW
authors: Bi
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Hang
authors: H
authors: Yang
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Xin
authors: X
authors: An
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Feng-Hua
authors: FH
authors: Wang
authors: State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine; Department of Medical Oncology, Sun Yat-Sen University Cancer Center.
authors: Wen-Qi
authors: WQ
authors: Jiang
keywords: BMI; ESCC; body mass index; esophageal squamous cell carcinoma; prognosis; smoking; survival