# 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

## TL;DR

This study examines whether total thyroidectomy and radioactive iodine are necessary for preventing cancer recurrence in intermediate-risk thyroid cancer patients with neck lymph node metastasis.

## Contribution

The study provides real-world evidence suggesting that radioactive iodine may not be necessary for intermediate-risk thyroid cancer patients with lateral neck lymph node metastasis.

## Key findings

- Five-year recurrence-free survival was 100% in patients who had total thyroidectomy without radioactive iodine.
- Propensity score analysis showed no significant benefit of radioactive iodine in preventing recurrence.
- Hemithyroidectomy combined with lymph node dissection had a 90.9% recurrence-free survival rate.

## Abstract

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).

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.

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).

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.