Trends in Imaging After Diagnosis of Thyroid Cancer

BACKGROUNDThe 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. METHODSUsing 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. RESULTSA 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. CONCLUSIONSDespite 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. Cancer 2015;121:1387-1394. (c) 2015 American Cancer Society. Using the Surveillance, Epidemiology, and End Results-Medicare database, the authors report that despite a rise in low-risk differentiated thyroid cancer, there has been a significant increase in the use of postdiagnosis imaging studies over the past 20 years. This is true for the 3 major imaging modalities used (neck ultrasound, radioiodine scan, and positron emission tomography), with the most dramatic increase noted in the use of positron emission tomography after 2004.