Incidental Thyroid Nodules in the National Lung Screening Trial

Publication date: Available online 27 March 2018
Source:Academic Radiology
Author(s): Manisha Bahl
Rationale and ObjectivesThere 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 MethodsCT 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.ResultsThyroid 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).ConclusionsLess 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.



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