Highly accurate NGS-based multi-gene testing in the diagnosis of thyroid nodules with indeterminate cytology.

e13579 Background: Thyroid nodules are highly prevalent, Fine-needle aspiration (FNA) is the standard pre-operative tool for diagnosis. However, some of the samples are classified as indeterminate, which leads to unnecessary surgery. BRAF V600E mutation is often used as a diagnostic marker for thyroid cancer, and it is highly specific for papillary thyroid carcinoma (PTC). But BRAF mutation is rarely occurred in thyroid nodules with indeterminate cytology. To diagnose the indeterminate thyroid nodules precisely, some NGS-based multi-gene testing panel has been developed and clinically used in America and Europe, but rare research was reported in China. In this study, we evaluated the value of a next-generation sequencing (NGS) panel to cancer diagnosis in indeterminate thyroid nodules. Methods: From February 2018 to September 2018, 360 patients with thyroid nodules who underwent FNA at Peking University Cancer Hospital were enrolled. And the FNA samples with indeterminate cytology were evaluated using a next-generation sequencing (NGS) assay, including 16 genes analyzed for point mutations and 26 types of gene fusions. Diagnostic performance of this multi-gene testing panel was compared with BRAF V600E single gene mutation analysis. Results: 141 nodules were cytologically indeterminate among 360 patients on FNA biopsy, 72 of which were resected and analyzed by NGS successfully. Histologic analysis after surgery revealed 41 (56.9%) cancers in these 72 patients. The multi-gene testing assay could classify 30/41 cancers correctly, showing a sensitivity of 73.2%, specificity of 96.8%, positive predictive value of 96.8%, and negative predictive value of 73.2%. The diagnostic accuracy of the multi-gene testing was significantly higher than the BRAF V600E mutation analysis (83.3% vs 73.6%, x 2 = 31.588, p < 0.01). Conclusions: Our study demonstrated that the multi-gene testing provided both high sensitivity and high specificity for cancer detection in thyroid nodules with indeterminate cytology, and its accuracy was much higher than BRAF V600E mutation test.