title: Trends in imaging after diagnosis of thyroid cancer.
abstract: BACKGROUND
  The largest growth noted among differentiated thyroid cancer (DTC) diagnosis is in low-risk cancers. Trends in imaging after the diagnosis of DTC are understudied. Hypothesizing a reduction in imaging use due to rising low-risk disease, the authors evaluated postdiagnosis imaging patterns over time and patient characteristics that are associated with the likelihood of imaging.
  
  
  METHODS
  Using the Surveillance, Epidemiology, and End Results-Medicare database, the authors identified patients diagnosed with localized, regional, or distant DTC between 1991 and 2009. Medicare claims were reviewed for use of neck ultrasound, iodine-131 (I-131) scan, or positron emission tomography (PET) scan within 3 years after diagnosis. Trends in imaging use were evaluated using regression analyses. Multivariable logistic regression was used to estimate the likelihood of imaging based on patient characteristics.
  
  
  RESULTS
  A total of 23,669 patients were included. Compared with patients diagnosed between 1991 and 2000, those diagnosed between 2001 and 2009 were more likely to have localized disease (P<.001) and tumors measuring <1 cm (P<.001). Use of neck ultrasound and I-131 scans increased in patients with localized disease (P ≤.001 and P = .003, respectively), regional disease (P<.001 and P<.001, respectively), and distant metastasis (P = .001 and P = .015, respectively). Patients diagnosed after 2000 were more likely to undergo neck ultrasound (odds ratio, 2.15; 95% confidence interval, 2.02-2.28) and I-131 scan (odds ratio, 1.44; 95% confidence interval, 1.35-1.54). Compared with 1996 through 2004, PET scan use from 2005 to 2009 increased 32.4-fold (P≤.001) in patients with localized disease, 13.1-fold (P<.001) in patients with regional disease, and 33.4-fold (P<.001) in patients with distant DTC.
  
  
  CONCLUSIONS
  Despite an increase in the diagnosis of low-risk disease, the use of postdiagnosis imaging increased among patients with all stages of disease. The largest growth observed was in the use of PET after 2004.
authors.affiliation: Division of Metabolism, Endocrinology, and Diabetes, University of Michigan, Ann Arbor, Michigan.
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Wiebel
authors.forename: Mousumi
authors.initials: M
authors.lastname: Banerjee
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Muenz
authors.forename: Francis P
authors.initials: FP
authors.lastname: Worden
authors.forename: Megan R
authors.initials: MR
authors.lastname: Haymart
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data / Q000639:trends; D018426:SEER Program; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging*
keywords: differentiated thyroid cancer; neck ultrasound; positron emission tomography (PET) scan; radioiodine scan; surveillance imaging