Hashimoto's thyroiditis on outcomes in papillary thyroid cancer revisited: experience from South East Asia

The association between Hashimoto Thyroiditis (HT) and papillary thyroid cancer (PTC) remains uncertain. HT, the most common inflammatory condition of the thyroid, is postulated to increase the risk of PTC and yet confer cancer-retarding effects. In this study, we aim to evaluate the prevalence of HT in patients surgically treated for PTC and evaluate the long-term prognostic implications.

This is a retrospective study of 521 patients with PTC who underwent hemi- or total thyroidectomy between January 2000 and December 2018 at a tertiary referral centre. Patients were categorised into two group: group A (n=402) consists of patients with PTC without HT, whereas group B (n=119) consists of patients with PTC and HT. Demographic and clinicopathological details, recurrence rates and overall survival were collected. Univariate and multivariate analyses were performed to evaluate for clinical factors associated with HT.

A total of 521 patients with a mean age of 46.7 years were evaluated. HT was detected in 22.8% of patients with PTC. On multivariate analysis, presence of HT was associated with a lower incidence of extrathyroidal extension (hazard ratio: 0.59, 95%confidence interval 0.37-0.95). Also, patients with HT tend to have fewer cycles of radioactive iodine and correspondingly have excellent response to treatment. However, no differences in recurrence rates and overall survival were detected.

One-fifth of patients with PTC have coexisting HT. These patients tend to have less-aggressive tumour features such as extrathyroidal extension. However, the effect of HT on recurrence and overall survival appears to be inconsequential clinically.