Clinical outcomes of radioactive 125 I seed brachytherapy for recurrent refractory differentiated thyroid cancers

[ Objective: ]The purpose of this research was to evaluate the feasibility and efficacy of 125I seed brachytherapy for recurrent refractory differentiated thyroid cancers. [ Methods ]:Between August 2005 and March 2023 33 patients with recurrence refractory of differentiated thyroid cancer were treated with 125I seed brachytherapy. 125I seeds were implanted into the tumor under the guidance of CT and/or 3D-printed template images with the median prescription dose of 126 Gy (range, 90-155 Gy). The median seed number was 54 (range 8-214). Clinical efficacy was evaluated with Response Evaluation Criteria in Solid Tumors. Follow-up Survival and adverse events were analyzed. [ Results: ] ¹²⁵ I seeds were successfully implanted in 44 lesions among 33 patients. Lesions included 34 cervical lymph node metastases, 2 cases of recurrent thyroid lesions, 2 cases of pulmonary metastases, 3 cases of bone metastases,1 cases of pleural metastases, 1 case of mediastinal lymph node involvement, and 1 case of back soft tissue metastasis. Patients were monitored for 6–96 months. Six months postoperatively, CT images revealed 26 cases of CR, 14 cases of PR, and 4 cases of Stable Disease (SD). The ORR was 90.9% (40/44), and the LCR reached 100% (44/44) at 6 months. The median OS was 40.7 months, with 1-year,2-year,3-year, 4-year and 5-year survival rates of 91%, 88%, 74%,64.5%,and 51%, respectively.14 patients had died due to systemic metastases.No severe complications occurred. [ Conclusions: ]CT-guided iodine-125 brachytherapy provided a safe and effective choice for recurrent refractory differentiated thyroid cancers with significant local therapeutic effects and minor complications.