Outcome of radioiodine therapy in patients with papillary thyroid carcinoma concurrent with Hashimoto's thyroiditis

Objective: To evaluate the impact of low-dose ¹³¹I therapy and high-dose ¹³¹I therapy on the clinical outcome in PTC patients coexisting with Hashimoto's thyroiditis (HT). Methods: A total of 140 non-distant metastatic PTC patients (16 males, 124 females, age range: 16-66 years) from July 2010 to December 2014 were enrolled in this retrospective study. Patients concurrent with HT (n = 84, group A) were divided into low-dose group (1110 MBq, n = 56, group A1) and high-dose group (5550 MBq, n = 28, group A2) according to ¹³¹I ablation dose. Patients without HT (n = 56) were enrolled as control group (group B), and received 1110 MBq of ¹³¹I. The thyroid remnant ablation outcome was evaluated according to ¹³¹I diagnostic whole-body scan (Dx-WBS), neck ultrasonography (US), serum Tg and TgAb level 6-8 months after ¹³¹I ablation therapy. The successful ablation rates were compared by χ² test. Kruskal-Wallis rank sum test was also used. Results: There were no significant differences among the 3 groups in terms of both clinicopathological features and postoperative remnant thyroid (H: 0.203-2.944, χ²: 0.271-0.970, all P > 0.05). When negative Dx-WBS and US were deemed as successful ablation criterion, complete ablation rate was found significantly more in group B (94.6%, 53/56) than that in group A1 (82.1%, 46/56; χ² = 4.264, P < 0.05), but no significant difference was found between group A2 (85.7%, 24/28) and group A1 (χ² = 0.318, P > 0.05). When combining negative sTg (sTg < 1 μg/L, TgAb < 46 kU/L) with the above 2 criterions to assess remnant ablation outcome, group B also had a higher successful rate to achieve complete ablation (85.7%, 48/56) compared with group A1 (75.6%, 34/45), but without statistical significance (χ² = 2. 978, P > 0.05), and no difference was observed between group A2 (12/15) and group A1 (χ² = 1.320, P > 0.05). Conclusion: Non-distant metastatic PTC patients coexisting with HT has undesirable ¹³¹I ablation outcome compared with those without HT, increasing ¹³¹I dose is unhelpful to enhance efficiency of remnant ablation for PTC patients with HT. (authors)