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Nodule size fails to influence gene-expression classifier performance
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A similar risk for malignancy was found between gene-expression classifier, or GEC, suspicious nodules larger than 3 cm and smaller nodules, according to study findings published in Thyroid.
“To date, little is known regarding the effect of clinical factors on the pre- and post-test probabilities of malignancy for nodules undergoing GEC testing,” the researchers wrote. “Clinical factors such as nodule size, patient demographics and cytologic features had the potential to interact with GEC performance, rendering the test more or less useful in certain subpopulations. There is a concern regarding larger nodules in particular, where GEC testing may have a lower negative predictive value due to sampling error. Alternatively, if the malignancy rate is very high in larger nodules that are GEC suspicious, total thyroidectomy may be considered as initial treatment rather than diagnostic lobectomy.”
James X. Wu, MD, of the section of endocrine surgery at UCLA David Geffen School of Medicine, and colleagues evaluated 230 adults (mean age, 51.9 years) who had cytologically indeterminate thyroid nodules and underwent GEC testing within the UCLA Medical Center between September 2012 and February 2015. Participants were only included if they had Bethesda category III or category IV thyroid nodules after fine-needle aspiration. Overall, 245 indeterminate thyroid nodules were evaluated, and most were Bethesda category III (n = 217).
Results of GEC testing revealed that 53.8% of the cases were suspicious and 46.2% were benign.
Testing of indeterminate nodules revealed a 95.2% sensitivity and 60.1% specificity for GEC testing with a 25.6% malignancy rate. Both the positive predictive value and negative predictive value were consistent across nodule size. There was a higher rate of suspicious GEC results among Hürthle-cell-predominant nodules compared with nodules without Hürthle cell predominance (P < .01); however, the rate of malignancy was similar between the two.
Nodule size was not predictive of malignancy in participants with GEC suspicious (OR = 1.13; 95% CI, 0.92-1.4) or GEC benign nodules (OR = 1.52; 95% CI, 0.83-2.79) in univariate analysis.
“GEC benign results remain reliable in large nodules. GEC suspicious nodules > 3 cm carry a similar risk of malignancy to smaller nodules and do not warrant more aggressive treatment,” the researchers wrote. “GEC testing has limited clinical utility for Hürthle-cell-predominant nodules due to the high rate of false-positive results.” – by Amber Cox
Disclosure: Wu reports no relevant financial disclosures. One researcher reports being a consultant to Veracyte Inc.
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