title: Association between smoking at diagnosis and cause-specific survival in patients with rectal cancer: Results from a population-based analysis of 10,794 cases.
abstract: BACKGROUND
  Currently, the 5-year survival rate for rectal cancer remains at <60%. The identification of potentially modifiable prognostic factors would be of considerable public health importance. A few studies have suggested associations between smoking and survival in rectal cancer; however, the evidence is inconsistent, and most of these studies were relatively small. In a large population-based cohort study, we investigated whether smoking at diagnosis is an independent prognostic factor for cancer-specific survival in rectal cancer and whether the association varies by sex, age, or treatment.
  
  
  METHODS
  Rectal cancers (ICD10 C19-20) diagnosed between 1994 and 2012 were abstracted from the National Cancer Registry Ireland and classified by smoking status at diagnosis. Follow-up was for 5 years or until December 31, 2012. Multivariable Cox proportional hazards models were used to compare cancer-specific death rates in current smokers, ex-smokers, and never smokers. Subgroup analyses by age at diagnosis, sex, and treatment were conducted.
  
  
  RESULTS
  A total of 10,794 rectal cancers were diagnosed. At diagnosis, 25% were current smokers, 24% were ex-smokers, and 51% were never smokers. Compared with never smokers, current smokers had a significantly greater rate of death from cancer (multivariable hazard ratio [HR], 1.15; 95% confidence interval [CI], 1.06-1.24), but ex-smokers did not (HR, 1.02; 95% CI, 0.94-1.11). The association was slightly stronger in men (current versus never smokers: HR = 1.13, 95% CI, 1.02-1.24) than females (HR, 1.05; 95% CI, 0.90-1.23), but the test for interaction was not significant (P = .75). The effect of smoking was not modified by age or receipt of tumor-directed surgery, radiotherapy, or chemotherapy.
  
  
  CONCLUSIONS
  Rectal cancer patients who smoke at diagnosis have a statistically significant increased cancer death rate. Elucidation of the underlying mechanisms is urgently required. Cancer 2017;123:2543-50. © 2017 American Cancer Society.
authors.affiliation: Institute of Health & Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Linda
authors.initials: L
authors.lastname: Sharp
authors.affiliation: National Cancer Registry Ireland, Cork, Ireland.
authors.forename: Joseph
authors.initials: J
authors.lastname: McDevitt
authors.affiliation: National Cancer Registry Ireland, Cork, Ireland.
authors.forename: Christopher
authors.initials: C
authors.lastname: Brown
authors.affiliation: ISGlobal, Centre for Research in Environmental Epidemiology, Barcelona, Spain.
authors.forename: Anne-Elie
authors.initials: AE
authors.lastname: Carsin
authors.affiliation: National Cancer Registry Ireland, Cork, Ireland.
authors.forename: Harry
authors.initials: H
authors.lastname: Comber
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use; D002423:Cause of Death; D015331:Cohort Studies; D013505:Digestive System Surgical Procedures; D005260:Female; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D016016:Proportional Hazards Models; D011878:Radiotherapy; D012004:Rectal Neoplasms / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D012007:Rectum / Q000601:surgery; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D015996:Survival Rate
chemical_list: D000970:Antineoplastic Agents
keywords: mortality; rectal cancer; smoking; survival; tobacco