title: Evaluation of the duplication of staging CT scans for localized colon cancer in a Medicare population.
abstract: BACKGROUND
  To quantify and characterize duplicated tests performed during the staging of localized colon cancer in the Medicare population.
  
  
  METHODS
  We used the SEER-Medicare linked database to select patients diagnosed with localized colon cancer between the years 1996 and 2009. We considered a patient as adequately staged after having received a colonoscopy, an abdominal computed tomography (CT) scan, and a pelvic CT scan. Abdominal and pelvic CT scans performed between complete staging and first cancer-directed treatment, if not ordered due to an acute condition, were considered duplicates. We characterized the institutions providing the tests and evaluated the association with survival using a weighted pooled logistic regression adjusted by baseline and time-varying confounders.
  
  
  RESULTS
  Of 36,291 patients with a complete staging, 2680 (7.4%) had at least 1 duplicated test. Patients receiving a duplicate had a higher comorbidity score, were more symptomatic, and had more visits to the emergency department and clinical evaluations. They also were treated with surgery less frequently and had worse survival (hazard ratio 1.22, 95% confidence interval, 1.16-1.28). The type of institution involved in the staging (nonprofit/government centers, proprietary centers, free-standing facilities) was not associated with receiving duplicated tests.
  
  
  CONCLUSIONS
  We found a low frequency of duplicated abdominal or pelvic CT scans in the staging of colon cancer in the Medicare population.
authors.affiliation: *Department of Epidemiology, Harvard School of Public Health †Dana Farber Cancer Institute ‡Department of Biostatistics, Harvard School of Public Health §Harvard-MIT Division of Health Sciences and Technology, Boston, MA.
authors.forename: Xabier
authors.initials: X
authors.lastname: García-Albéniz
authors.forename: Roger W
authors.initials: RW
authors.lastname: Logan
authors.forename: Deborah
authors.initials: D
authors.lastname: Schrag
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Hernán
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D009367:Neoplasm Staging / Q000379:methods / Q000706:statistics & numerical data*; D018426:SEER Program; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D014481:United States / Q000453:epidemiology; D019564:Unnecessary Procedures / Q000706:statistics & numerical data*