Impact of extent thyroidectomy and radioactive iodine ablation for disease free survival in the intermediate-risk patients with lateral neck lymph node metastasis: a retrospective and tentative real-world approach.

[BACKGROUND] It is controversial whether or not total thyroidectomy followed by radioactive iodine ablation (RAI-a) (30 mCi = 1.1 GBq) is mandatory in intermediate-risk patients with lateral neck lymph node metastasis (cN1b).

[METHODS] This retrospective observational study enrolled PTC patients classified preoperatively as the intermediate-risk with cN1b from January 2010 to December 2017 according to the guidelines for thyroid tumors of the Japanese Association of Endocrine Surgeons (JAES) since 2009. We analyzed recurrence-free survival (RFS) rates estimated by the Kaplan-Meier method in the patients classified into three groups: 1) total thyroidectomy (TTx) followed by lateral neck lymph node dissection (LLND) with RAI-a, 2) TTx + LLND without RAI-a, 3) hemithyroidectomy + LLND. In addition, propensity score analysis adjusted by clinical parameters was performed.

[RESULTS] Two hundred eighty-eight patients with intermediate-risk PTC were identified. Among them, 87 patients with cN1b were analyzed. Five-year RFS rates in 1), 2), and 3) groups were 85.0%, 100%, and 90.9%, respectively. The analysis of 1) and 2) groups by propensity score matching revealed 5-yr RFS rates of 84.1% and 100%, respectively (p < 0.0432).

[CONCLUSIONS] There was no evidence to support the use of 30 mCi (1.1GBq) radioactive iodine postoperatively to prevent recurrence in intermediate-risk PTC patients with cN1b.