Trends in imaging after diagnosis of thyroid cancer

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.