Recurrence following hemithyroidectomy in patients with low‐ and intermediate‐risk papillary thyroid carcinoma

BACKGROUND: This study evaluated the incidence, patterns and risk factors for recurrence after hemithyroidectomy in patients with low- and intermediate-risk papillary thyroid carcinoma (PTC), and verified the predictive role of the risk staging systems in current use. METHODS: The clinicopathological characteristics and risk categories were analysed according to recurrence in patients who underwent hemithyroidectomy for low- and intermediate-risk conventional PTC, and were followed up for at least 24 months. Five risk staging systems were used to stratify risk: the 2015 American Thyroid Association (ATA) system; Age, Metastases, Extent and Size (AMES) system; Metastases, Age, Complete resection, Invasion and Size (MACIS) system; Grade, Age, Metastases, Extent and Size (GAMES) system; and the eighth AJCC system. RESULTS: The study included 561 patients; 93.9 per cent of the study population (527 of 561) had a papillary thyroid microcarcinoma 1 cm or smaller in size. At a mean follow-up of 83 months, 25 patients (4.5 per cent) had recurrence; among these patients, 23 (92%) presented with a remaining thyroid lobe. Multifocality was significantly associated with recurrence in univariable and multivariable analyses (adjusted hazard ratio 3.16, 95 per cent c.i. 1.25 to 7.98; P = 0.015). Disease-free survival (DFS) varied according to multifocality (P = 0.010). The five risk staging systems were not associated with recurrence, and their Harrell's C-index ranged from 0.500 to 0.531. DFS rates did not differ between the risk categories in each system. CONCLUSION: Although the recurrence rate after hemithyroidectomy in patients with low- and intermediate-risk PTC was low, meticulous follow-up focusing on the remaining thyroid lobe is needed for early detection and timely management of recurrence. The risk scoring systems in current use have no predictive role in these patients.