PSAT267 Performance of ThyroSeq V3 molecular testing in assessing indeterminate thyroid nodules for thyroid cancer at an urban endocrinology clinic.

INTRODUCTION: While fine needle aspiration (FNA) biopsy can accurately classify thyroid nodules as benign versus malignant in most cases, roughly 20% of cases remain indeterminate. Molecular testing can assist with risk stratification of indeterminate nodules, with the goal to identify benign nodules and therefore decrease further testing. We aimed to validate the accuracy of ThyroSeq v3 molecular testing for predicting malignancy in real-world practice in a diverse, urban setting. METHODS: This was a retrospective, cohort study of 41 adults with 43 indeterminate thyroid nodules, for which molecular analysis using the multigene classifier (GC) ThyroSeq v3 was performed at an outpatient endocrinology practice in San Francisco, CA between December 2011 and December 2021. The primary outcome was positive predictive value for malignancy in indeterminate thyroid nodules, using ThyroSeq v3. The secondary outcome was prediction of cancer by specific genetic alterations. RESULTS: Most patients were female (78.0%), with a median age of 56 years (range 30-84). Nodules were classified as low (n=28; 65.1%), low-intermediate (n=2; 4.7%), or intermediate-high (n=12; 27.9%) risk for malignancy using ThyroSeq v3. Risk could not be assessed in one nodule due to inadequate sample[1] . Of patients with low-risk nodules, only 1 underwent total thyroidectomy due to compressive symptoms[2] . Of patients with low-intermediate or intermediate-high risk nodules, most (13/14) underwent surgical resection[3] . Papillary thyroid cancer was identified in 72.7% (8/11) patients with intermediate-high risk nodules who underwent surgery. In patients with papillary thyroid cancer, the most common mutation was BRAF V600E (n=5). Among indeterminate nodules (Bethesda III and IV cytology[4]), the positive predictive value of ThyroSeq v3 was 54.5%[5] . CONCLUSIONS: Of patients with thyroid nodules of indeterminate risk based on FNA biopsy and intermediate to high risk for malignancy as determined by ThyroSeq v3 molecular sequencing, most underwent surgical resection and were found to have thyroid cancer in most cases, with BRAF V600E being the most common mutation. ThyroSeq v3 is a useful stratification tool for those patients with indeterminate nodules. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.