Abstract 33
Authors: Kannan Subramanian , Aggarwal Suruchi , Shivaprasad KS , Sooragonda Basavaraj , Khadilkar Kranti , Gondaliya Hetashvi 
Published: February 2023

Background: Molecular testing is recommended in the management of indeterminate thyroid nodules (Bethesda III & IV) to decide between surgery (suspicious molecular pattern) or observation (benign molecular pattern). It is also useful in Anaplastic (ATC)/Dedifferentiated thyroid cancers (to assess BRAF, TSC1, TSC2, ALK fusion genes, NTRK fusion genes, and RET fusion genes) in deciding targeted therapies. Despite the wide spread use in the western world, the availability of cost-effect molecular panel in the setting of thyroid nodule/cancer has been a limiting factor in India. We report our pilot results using the Thyro Track in our Thyroid nodule/cancer clinic from July 2022.

Methods: Thyro Track is a thyroid prognostication NGS panel covering 40 unique genes for Single Nucleotide Variations (SNV) and Deletions (InDels) (including BRAF, RAS and P13K pathway genes) and 17 genes for known and unknown fusions including the RET, NTRK, ALK and other genes. Consenting patients with indeterminate thyroid nodules, sonographically suspicious Bethesda II nodules or high-grade thyroid cancer were subjected for molecular testing (n = 19). Molecular testing was performed on the FNAC material (n = 14), Core Biopsy material (n = 2) and Histopathology blocks (HPE) (n = 3).

Results: Results of the NGS testing are awaited in 3 samples (at time of abstract submission; Two with ATC, one with Bethesda II nodule), the material was insufficient in 2 patients (one of them with Bethesda II and the other patient nodule resolved suggesting thyroiditis). NGS done on aggressive thyroid cancers revealed, one had BRAFV600E (60 year female with PTC with areas of de-differentiation, status post thyroidectomy and radio-iodine ablation with radio-iodine refractory lung metastasis), one had dual mutation of NRAS p.Gln61Lys & PTEN p.Arg130Pro (63 year female locally advanced FVPTC with areas of de-differentiated areas subjected primarily radiation and doxorubicin based chemotherapy as the mass was inoperable) and the third case had dual mutation of NRASp.GIn61Arg & PIK3CA p.His1047Arg (52 year old female with widely metastatic ATC who died within a month of diagnosis). Among the 11 patients with indeterminate thyroid nodules (Bethesda III n = 9; Bethesda IV n = 2), the mean size of the nodules was 3.8 cm (1.2-6), with ACR-TIRADS score of TR3 (n = 4), TR4 (n = 5), TR5 (n = 2). NGS panel was negative in 5 patients. 4 patients have been advised sonographic follow up as their nodules are either TR3 or TR4 and one patient with TR5 nodule underwent surgery; final HPE was encapsulated FVPTC (Mutation analysis of the HPE block was also done). Among those with positive NGS (n = 6), the predominant mutations were in the RAS genes (NRAS n = 4; HRAS n = 1; TP53 n = 1). All these patients have been advised hemithyroidectomy.

Conclusion: NGS based molecular panel done either on FNAC material or HPE blocks offers useful insights in the molecular signatures of these nodules/cancers. Widespread adoption of genetic testing will help establishing diagnostic sensitivity and specificity for this panel.