# Prognostic significance of minimal extrathyroidal extension in differentiated thyroid carcinoma: a retrospective cohort study

## TL;DR

This study finds that minimal extrathyroidal extension in thyroid cancer is linked to worse outcomes in some cases, but it's not a strong enough predictor to guide treatment decisions alone.

## Contribution

The study clarifies that minimal extrathyroidal extension is not an independent predictor of poor outcomes in thyroid cancer patients.

## Key findings

- Patients with minimal extrathyroidal extension had higher recurrence rates in univariate analysis.
- Minimal extrathyroidal extension was not an independent predictor of structural recurrence in multivariate analysis.
- Disease-free survival was significantly worse in patients with minimal extrathyroidal extension.

## Abstract

•Minimal ETE is associated with adverse risk features in thyroid carcinoma.•Patients with minimal ETE had higher recurrence rates in univariate analysis.•Minimal ETE was not an independent predictor of poor outcomes.•Risk stratification should not rely solely on the presence of minimal ETE.

Minimal ETE is associated with adverse risk features in thyroid carcinoma.

Patients with minimal ETE had higher recurrence rates in univariate analysis.

Minimal ETE was not an independent predictor of poor outcomes.

Risk stratification should not rely solely on the presence of minimal ETE.

To evaluate the impact of minimal Extrathyroidal Extension (mETE) on structural recurrence, prognostic variables, and disease-free survival in patients with Differentiated Thyroid Carcinoma (DTC) treated surgically.

A retrospective cohort of 629 patients who underwent thyroidectomy for DTC was analyzed. Patients were divided into two groups: Group 1 (n = 413) with tumors confined to the thyroid, and Group 2 (n = 216) with minimal extrathyroidal extension. Clinical, pathological, and biochemical variables were compared between groups. The minimum follow-up period was 30-months or until death, with an average follow-up of 71.5-months. Univariate and multivariate analyses were performed to identify independent predictors of structural recurrence.

Structural recurrence occurred in 6.5% of Group 1 and 22.7% of Group 2 patients (p < 0.001). Group 2 showed significantly higher rates of follicular carcinoma, tumor size > 2 cm, angiolymphatic invasion, pN1 disease, multicentricity, elevated postoperative thyroglobulin (Tg > 10 ng/mL), iodine-refractory disease, distant metastases, and higher late Tg levels (all p < 0.05). Even though the univariate associations were statistically significant, multivariate analysis identified only male sex (p = 0.018), postoperative Tg >10 ng/mL (p < 0.001), and iodine-refractory disease (p < 0.001) as independent predictors of structural recurrence, not mETE. Five-year disease-free survival was 94.1% in Group 1 and 79.2% in Group 2 (p < 0.001).

Minimal extrathyroidal extension was associated with several adverse prognostic factors and worse outcomes in univariate analysis. However, it was not an independent predictor of structural recurrence or reduced disease-free survival in this cohort. These findings highlight the need to understand mETE in the larger context of risk stratification in management of DTC.

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