Restratification of intermediate risk factors on the recurrence of papillary thyroid carcinoma: a retrospective cohort study

Background: Data regarding the long-term recurrence in patients with intermediate-risk papillary thyroid carcinoma (PTC) are limited. The aim of this study was to assess the impact of primary tumor-related risk factors and lymph node (LN)-only risk factors on recurrence-free survival (RFS) in patients with intermediate-risk PTC. Materials and methods: Patients with PTC who received initial treatment at our institution between 2010 and 2016 were retrospectively reviewed. A total of 799 intermediate-risk PTC patients were included and further categorized into subgroups according to the different categories of intermediate-risk factors. The RFS rates of these subgroups were investigated and compared. Results: Structural recurrence developed in 11 patients (1.4%) of the whole cohort during a median follow-up duration of 96 months. There were no significant differences in RFS between the primary tumor-only risk group and the LN-only risk group, while the combined group of primary tumor risk factors and LN risk factor (metastatic LNs >5) was associated with a worse RFS rate. In the matched-pair analysis, no significant difference in RFS was found between patients who underwent thyroid lobectomy and those who underwent total thyroidectomy (6-year RFS: 99.6 vs. 98.8%, P=0.316) during a median follow-up duration of 100 months. Conclusions: Intermediate-risk PTC patients who underwent thyroid lobectomy had a comparable RFS to those who underwent total thyroidectomy. The combination of primary tumor risk factors and LN risk factor (metastatic LNs >5) may be a useful tool for predicting the risk of long-term structural recurrence in patients with intermediate-risk PTC.