Ultrasound-guided implantation of radioactive 125 I seed in radioiodine refractory differentiated thyroid carcinoma

Background: Treatment for radioiodine refractory differentiated thyroid carcinoma (RR-DTC) is challenging. The purpose of this study was to assess the efficacy and safety of ultrasound-guided implantation of radioactive 125 I-seed in radioiodine refractory differentiated thyroid carcinoma. Methods: 36 cervical metastatic lymph nodes (CMLNs) diagnosed as RR-DTC from 18 patients were enrolled in this retrospective study. US and contrast-enhanced ultrasound (CEUS) examinations were performed before implantation. Follow-up consisted of US, CEUS, thyroglobulin (Tg) level and routine hematology at 1-3, 6, 9 and 12 months and every 6 months thereafter. The volumes of the nodules were compared before implantation and at each follow-up point. The volume reduction rate (VRR) of nodules was also recorded. Results: The median volume of the nodules was 522.8 mm 3 (147.5, 2009.6mm 3 ) initially, which decreased significantly to 53.0mm 3 (0, 285.7mm 3 ) (P < 0.01) at the follow-up point of 24 months with a mean VRR as 87.4±18.1% (the range was 32–100%). During the follow-up period (the range was 24–50 months), 25 (69%) nodules had VRR greater than 90%, of which 12 (33%) nodules had VVR≈100% with structures unclear and only 125 I seeds images visible. At the last follow-up visit, the serum Tg level decreased from 57.0 (8.6, 114.8) ng/ml to 4.9 (0.7, 50.3) ng/ml, (P < 0.01). Conclusion: US-guided 125 I seed implantation is safety and efficacy in treating RR- DTC. It could be an effective supplement for the comprehensive treatment of thyroid cancer.