Thyroid cancer is the most common endocrine neoplasm. The annual rate of new cases of thyroid cancer is 13.9 per 100,000 men and women [1]. In 2020, there were 586,200 new cases of thyroid cancer in 185 countries; thyroid cancer accounted for 3.0 % of all cancers and ranked 11th in terms of the global incidence of cancer [2]. At least 94 % thyroid cancers are differentiated thyroid carcinomas (DTCs) [[3], [4], [5]]. Although the majority of thyroid cancers have an excellent prognosis, 5 %–15 % DTCs and 50 % metastatic DTCs become refractory to radioactive iodine (RAI) treatment [RAI-refractory (RAIR) DTC (RAIR-DTC)] [[5], [6], [7], [8], [9], [10]], resulting in a significant negative impact on the prognosis and a mean life expectancy of 3–5 years [8,11,12]. RAIR-DTC has become a global concern [13], with the lack of alternative effective and safe treatment choices constituting a significant challenge in terms of management [3]. Therefore, timely diagnosis of RAIR-DTC can prevent unnecessary RAI therapy and enable patients to receive an effective treatment regimen involving targeted therapies as early as possible [7,14]. Although RAI-refractory patients should not receive any further 131I treatment, the timing of RAI treatment termination is problematic and controversial [12,15,16]. Most RAIR-DTC diagnoses are based on multiple episodes of unsuccessful RAI therapy. Detailed intra- or postoperative evaluation of relevant clinicopathological data for timely prediction evaluation of the effects of 131I treatment, as well as timely and accurate treatment of DTC, have become important strategies for RAIR-DTC treatment. Although some clinicopathological features of DTC are reportedly helpful for the early prediction of iodine refractoriness [3,5,7,14,[17], [18], [19]], their usefulness remains highly controversial.

The aim of this study was to collect and analyze the clinical and pathological characteristics of RAIR-DTC in order to provide clinical evidence for timely prediction of the effects of RAI therapy.