# Hashimoto Thyroiditis and Progression of Papillary Thyroid Cancer: 10-Year Retrospective Cohort Study

## TL;DR

This study found that Hashimoto thyroiditis does not generally increase papillary thyroid cancer progression during active surveillance, but the risk may be higher in overweight or obese patients.

## Contribution

The study identifies a potential interaction between Hashimoto thyroiditis and BMI in influencing papillary thyroid cancer progression during active surveillance.

## Key findings

- No significant association was found between Hashimoto thyroiditis and papillary thyroid cancer progression overall.
- Overweight or obese patients with Hashimoto thyroiditis had a significantly increased risk of disease progression.
- Subgroup analyses revealed a potential effect modification by BMI on the relationship between Hashimoto thyroiditis and cancer progression.

## Abstract

In recent years, the global incidence of thyroid cancer has been increasing.

This study aimed to examine the association between Hashimoto thyroiditis (HT) and papillary thyroid cancer (PTC) progression under active surveillance (AS).

Our retrospective study was conducted at Peking University Third Hospital and included 203 patients with PTC who underwent AS for ≥6 months before surgery. Patients were first categorized into 2 groups: the HT group (n=90) and the non-HT group (n=113). Cox proportional hazards models were then used to evaluate the association between HT and PTC progression during AS, adjusting for age, sex, baseline tumor size, BMI, pregnancy status, number of tumor foci, and thyroid-stimulating hormone level. Subgroup analyses stratified by the 6 covariates mentioned above were also applied to explore the potential effect modification.

No significant difference was observed between the HT and non-HT groups in PTC progression-free survival (hazard ratio [HR] 1.11, 95% CI 0.61‐1.99; P=.74), tumor enlargement-free survival (HR 1.02, 95% CI 0.56‐1.86; P=.95), or lymph node metastasis-free survival (HR 1.76, 95% CI 0.31‐10.12; P=.52). Subgroup analyses revealed a potential interaction between HT and BMI. Among patients who were overweight or obese (BMI >24 kg/m²), HT was significantly associated with an increased risk of disease progression (HR 6.32, 95% CI 1.84‐21.69; P=.003), while among patients with BMI ≤24 kg/m2, no association between HT and progression risk was observed (P=.01).

We found no evidence of association between HT and PTC progression during AS. However, the relationship between HT and PTC progression may be modified by overweight or obesity status.