title: Risk of esophageal adenocarcinoma in achalasia patients, a retrospective cohort study in Sweden.
abstract: OBJECTIVE
  Achalasia is a motor disorder of the lower esophageal sphincter, which fails to relax on swallowing. Although a greater risk of esophageal squamous cell carcinoma among achalasia patients is fairly well established, no epidemiological study has evaluated the risk of esophageal adenocarcinoma in these patients.
  
  
  METHODS
  We compiled a cohort of 2,896 patients recorded with a discharge diagnosis of achalasia between 1965 and 2003 in the Swedish Inpatient Register. The cohort was followed through 2003 via record linkages with essentially complete registers of cancer, causes of death, and migration. Standardized incidence ratios (SIRs) were used to estimate the relative risk of esophageal cancer in achalasia patients compared to the age-, sex-, and calendar period-matched Swedish population. We further estimated SIRs for esophageal cancer among patients treated with esophagomyotomy.
  
  
  RESULTS
  After excluding the first year of follow-up, we observed excess risks for both squamous cell carcinoma (SIR 11.0, 95% confidence interval [CI] 6.0-18.4) and adenocarcinoma (SIR 10.4, 95% CI 3.8-22.6) of the esophagus. Notwithstanding similar numbers of men and women in our achalasia cohort, 20 of 22 esophageal cancers developed in men (SIRs for adenocarcinoma and squamous cell carcinoma were 8.4 and 13.1, respectively). Increased SIRs among operated patients pertained mainly to esophageal squamous cell carcinoma. We found no evidence that surgical esophagomyotomy increases the risk of esophageal adenocarcinoma.
  
  
  CONCLUSIONS
  Male achalasia patients have substantially greater risks for both squamous cell carcinoma and adenocarcinoma of the esophagus. Small numbers preclude a firm conclusion about the risk among women.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kazem
authors.initials: K
authors.lastname: Zendehdel
authors.forename: Olof
authors.initials: O
authors.lastname: Nyrén
authors.forename: Annika
authors.initials: A
authors.lastname: Edberg
authors.forename: Weimin
authors.initials: W
authors.lastname: Ye
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology* / Q000473:pathology* / Q000601:surgery; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D015331:Cohort Studies; D016001:Confidence Intervals; D004931:Esophageal Achalasia / Q000453:epidemiology* / Q000473:pathology* / Q000601:surgery; D004938:Esophageal Neoplasms / Q000453:epidemiology* / Q000473:pathology* / Q000601:surgery; D016629:Esophagectomy / Q000379:methods / Q000401:mortality; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011230:Precancerous Conditions / Q000453:epidemiology / Q000473:pathology / Q000601:surgery; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D017678:Sex Distribution; D015996:Survival Rate; D013548:Sweden / Q000453:epidemiology