LBODP092 Proposal Of Indication For Completion Thyroidectomy In Follicular Thyroid Carcinoma Using TERT Promoter Mutational Status

Abstract Background Stepwise surgical approach with hemithyroidectomy and completion thyroidectomy was used to solve the dilemma of definite characterization of follicular thyroid carcinoma (FTC). However, which patients will be candidates for completion thyroidectomy has been controversial. The aim of this study is to clarify the selection criteria for completion thyroidectomy using TERT promoter mutation. Methods A total of 87 FTC patients who had information about TERT promoter mutation from August 1995 to November 2020 were investigated. The cumulative risk of initial distant metastasis, disease recurrence, and cancer-specific death according to primary tumor size in each of the WHO 2017 classifications were calculated. Results Of the 87 patients, 8 patients (9.2%) had initial distant metastasis, and 15 patients (17.2%) had persistent disease or developed structural recurrence. Threshold diameter for initial distant metastasis, disease recurrence, and cancer-specific death was 2cm in minimally invasive FTC (MI-FTC) with mutant TERT (M-TERT) and in encapsulated angioinvasive FTC (EA-FTC) with M-TERT, while in MI-FTC with wild-type TERT (WT-TERT) and EA-FTC with WT-TERT it was 4cm. Cumulative risk of initial distant metastasis, disease recurrence, and cancer-specific death according to primary tumor size in each WHO 2017 classification were significantly different only in patients with WT-TERT (P = 0. 001, P = 0. 019, and P = 0. 005, respectively). Conclusions The data suggested that 2 cm may be a critical threshold diameter for deciding completion thyroidectomy in MI-FTC with M-TERT and EA-FTC with M-TERT. TERT promoter mutational status can be a game changer for selecting candidates for completion thyroidectomy. Presentation: No date and time listed