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Hashimoto’s thyroiditis associated with favorable outcomes in papillary thyroid carcinoma
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Researchers in South Korea reported that the presence of Hashimoto’s thyroiditis was linked with favorable outcomes in patients with papillary thyroid carcinoma regardless of the number of metastatic lymph nodes or extent of dissection.
“Although it is an ongoing debate, the coexistence of [Hashimoto’s thyroiditis] is known to be a risk factor for the development of [papillary thyroid carcinoma], but it is also regarded as a factor associated with favorable outcome,” Tae Yong Kim, MD, PhD, professor at the University of Ulsan College of Medicine, Seoul, and colleagues wrote.
The researchers conducted a retrospective cohort study of patients with papillary thyroid carcinoma (PTC) who underwent total thyroidectomy with prophylactic central compartment node dissection at Asan Medical Center in Seoul between 2005 and 2008 (n = 1,369). Kim and colleagues evaluated the extent of lymph node dissection and metastasis using the metastatic lymph node ratio, defined as the number of metastatic lymph nodes divided by the number of removed nodes. They also assessed clinical outcomes using disease-free survival and dynamic risk stratification.
The risk for cervical lymph node metastasis was similar among patients with Hashimoto’s thyroiditis and those without (61.6% vs. 65.1%; P = .292). However, patients with Hashimoto’s thyroiditis had significantly more lymph nodes removed than those without, Kim and colleagues wrote (11 vs. 8; P < .001). As a result, patients with Hashimoto’s thyroiditis had a smaller metastatic lymph node ratio (P = .002). This was associated with recurrent or persistent disease (HR = 2.33; 95% CI, 1.3-4.16). However, after adjusting for other clinicopathological features, Hashimoto’s thyroiditis was associated with a significantly lower risk for structural persistent or recurrent disease (HR = 0.39; 95% CI, 0.18-0.87), the researchers reported.
Furthermore, patients with Hashimoto’s thyroiditis had significantly superior disease-free survival compared with those without (HR=0.47; 95% CI, 0.27-0.8).
“Our findings confirm that [Hashimoto’s thyroiditis] itself is a favorable prognostic factor for PTC,” the researchers wrote. – by Andy Polhamus
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Historically there have been conflicting data on the relationship between Hashimoto’s thyroiditis and papillary thyroid cancer prognosis. Part of the variability in study findings is secondary to differences in the definition of Hashimoto’s thyroiditis. Some studies define Hashimoto’s thyroiditis based on pathology, others based on antibody status, and others based on ultrasound findings. In this study, the authors define Hashimoto’s thyroiditis based on pathology report. They evaluate the relationship between papillary thyroid cancer with and without Hashimoto’s thyroiditis and the patients’ dynamic risk stratification and disease-free survival. There was no significant difference in the proportion of patients within each risk category; however, with a median of 8 years of follow-up, disease-free survival was significantly better in patients with Hashimoto’s compared to those without. Strengths of this study include the use of the dynamic risk stratification and the evaluation of metastatic lymph node ratios. Limitations include the relatively small number of patients with recurrent/persistent disease.
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