Prognosis of papillary thyroid cancer in patients with Graves’ disease: a propensity score-matched analysis

Background: Patients with Graves’ disease (GD) are at a 2.5 times higher risk of developing thyroid cancer than the general population. Previous studies reported conflicting results about the prognosis of thyroid cancer concomitant with GD. This study aimed to investigate the effect of GD to the recurrence rates of papillary thyroid carcinoma (PTC). Methods: We reviewed 3628 patients who underwent total thyroidectomy for PTC at the Ewha Womans University Medical Center from January 2006 to June 2014. Of those, 114 patients had non-occult PTC with concomitant GD. To reduce potential confounding effects and selection bias, we conducted 1:5 propensity score matching and analyzed the recurrence-free survival. Results: Thyroid cancer in patients with GD showed lower rate of lymphatic invasion (1.8% vs. 6.7%; p = 0.037), microscopic resection margin involvement (0.9% vs. 5.8%; p = 0.024), and lymph node metastasis (29.8% vs. 37.3%; p = 0.001) than in patients without GD, respectively. During the median follow-up of 94.1 months, recurrence occurred in one patient (0.9%) with GD. After propensity score matching for adjusting clinicopathological features, 5-year recurrence-free survival was comparable between patients with GD and euthyroid patients (100% vs. 98.4%, p = 0.572). Both tumor size [hazard ratio (HR) 1.585, p < 0.001] and lymph node metastasis (HR for N1a 3.067, p = 0.024; HR for N1b 15.65, p < 0.001) were predictive factors for recurrence-free survival, while GD was not associated with the recurrence. Conclusions: Our data suggest that GD does not affect the prognosis of PTC. Thyroid cancer in patients with GD is not more aggressive than in euthyroid patients.