Rationale and Objectives
There is limited research on the prevalence of incidental thyroid nodules (ITNs) in the United States screening population and on the appropriate evaluation of computed tomography (CT)-detected ITNs. The purpose of this study is to determine the prevalence of ITNs in the National Lung Screening Trial (NLST) and develop a workup strategy for ITNs.
Materials and Methods
CT images were obtained for subjects with documented thyroid abnormalities in the CT screening arm of the NLST, subjects diagnosed with thyroid malignancies, and control subjects. Several size thresholds were compared to determine how many nodules would be further evaluated and how many thyroid malignancies would be missed had each threshold been applied at the time of workup.
Results
Thyroid nodules were reported in 0.7% (117 of 17,309 subjects). In 663 control subjects without reported thyroid nodules, thyroid nodules were identified in 78 (11.8%). Reported nodules were larger than unreported nodules (21.3 vs 16.9 mm, P = .03). Thyroid malignancies were diagnosed in 0.1% (22 of 17,309). If a 20-mm rather than a 10-mm cutoff were used to determine which nodules should be further evaluated, all malignancies would be detected, but 24 rather than 62 patients would require workup, for a workup reduction rate of 48.7% (38 of 78).
Conclusions
Less than 1% of subjects in the NLST had reported ITNs. The true prevalence of ITNs was estimated to be 11.8%, which provides a better approximation of the number of patients who could potentially receive workup. A 20-mm rather than a 10-mm cutoff would reduce the workup rate by almost 50% while still capturing all malignancies.
Introduction
A commonly encountered incidental finding on chest computed tomography (CT) examinations is the incidental thyroid nodule (ITN) . The majority of imaging-detected ITNs are benign, but the possibility of malignancy can prompt further evaluation with ultrasound and fine needle aspiration biopsy (FNAB) . If the FNAB results are not conclusive, additional tests and interventions may ensue, including ultrasound surveillance, repeat FNAB, and even surgery for histopathologic diagnosis .
There are currently no studies on the prevalence of ITNs in the United States lung screening population. Several European and Canadian CT lung screening trials, the largest of which had 5200 trial participants, found that ITNs are reported in less than 5% of patients . Furthermore, there is limited research on the appropriate workup and management of ITNs identified on CT, which has led to variable reporting practices among radiologists .
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Materials and Methods
Study Population
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Study Design, Data Collection, and Image Interpretation
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Statistical Analysis
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Results
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TABLE 1
Comparison of Nodule Sizes to Direct Further Workup of Incidental Thyroid Nodules
Size of Thyroid Nodule Nodules Requiring Workup (%) Detected Malignancies (%) ≥10 mm 62/78 (79.5%) 16/16 (100%) ≥15 mm 42/78 (53.8%) 16/16 (100%) ≥20 mm 24/78 (30.8%) 16/16 (100%) ≥25 mm 17/78 (21.8%) 13/16 (81.3%)
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Discussion
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Acknowledgments
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