Outcomes of Cytologically Indeterminate Thyroid Nodules Managed With Genomic Sequencing Classifier

Context: Molecular testing can refine the risk of malignancy in thyroid nodules with indeterminate cytology to decrease unnecessary diagnostic surgery. Objective: This study was performed to evaluate the outcomes of cytologically indeterminate thyroid nodules managed with Afirma genomic sequencing classifier (GSC) testing. Methods: Adult patients who underwent a biopsy at 3 major academic centers between July 2017 and June 2021 with Bethesda III or IV cytology were included. All patients had surgery or minimum follow-up of 1 year ultrasound surveillance. The primary outcomes were the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of GSC in Bethesda III and IV nodules. Results: The median nodule size of the 834 indeterminate nodules was 2.1 cm and the median follow-up was 23 months. GSC sensitivity, specificity, PPV, and NPV across all institutions were 95%, 81%, 50%, and 99% for Bethesda III nodules and 94%, 82%, 65%, and 98% for Bethesda IV nodules, respectively. The overall false-negative rate was 2%. The NPV of GSC in thyroid nodules with oncocytic predominance was 100% in Bethesda III nodules and 98% in Bethesda IV nodules. However, the PPV of oncocytic nodules was low (17% in Bethesda III nodules and 45% in Bethesda IV nodules). Only 22% of thyroid nodules with benign GSC results grew during surveillance. Conclusion: GSC is a key tool for managing patients with indeterminate cytology, including the higher-risk Bethesda IV category. GSC-benign thyroid nodules can be observed similarly to thyroid nodules with benign cytology.