Clinical Efficacy Of ¹²⁵I Seed Implantation In The Treatment Of Refractory Differentiated Thyroid Cancer

Objective:To evaluate the clinical efficacy of ¹²⁵I seed implantation in the treatment of refractory differentiated thyroid cancer.Methods:It was a retrospective review of 73 lesions from 36 patients with refractory differentiated thyroid cancer at our department from January 2015 to February 2022,treated with CT-guided ¹²⁵I seed implantation,including 4 lesions of local recurrence,19 lesions of lymph node metastases,4 lesions of lung metastases,42 lesions of bone metastases and 4 lesions of pleural metastases.The three-dimensional treatment planning system（TPS）was used for preoperative planning design with prescription dose from 80Gy to 120Gy.Follow-up comprised cervical ultrasound,CT scan of the implanted site,routine hematology,thyroglobulin（Tg）/thyroglobulin antibody（Tg Ab）level and pain score at the first,third,and fifth month after operation.Other than simple destruction of bone lesions,Response Evaluation Criteria for Solid Tumors（RECIST 1.1 criteria）was used to evaluate the local tumor response of local recurrent lesions,metastatic lymph nodes,lung metastases,pleural metastases and bone metastases with soft tissue formation.The changes of serum non-stimulate Tg（Tg Ab-）and pain score were also analyzed,and the data were expressed as[Md（Q₁,Q₃）]by rank sum test.Results:1.Other than 14 simple destruction of bone lesions,the size of 59 tumor lesions measured by CT at the first,third and fifth month after ¹²⁵I seed implantation revealed that CR,PR,SD,PD were 0,14,44,1 at the first month,accounting for 0%,23.73%,74.58%,1.69%;CR,PR,SD,PD were 6,17,34,2 at the third month,accounting for10.17%,28.81%,57.63%,3.39%;CR,PR,SD,PD were 11,20,25,3 at the fifth month,accounting for 18.64%,33.90%,42.37%,5.08%.The local effective rate at the first,third,and fifth month following treatment was 23.73%,38.98%,52.54%,respectively.The local control rate was separately 98.31%,96.61%,94.92%.2.Serum Tg of 36 patients before ¹²⁵I seed implantation was 249.45（79.39,4718.75）ng/m L,and Tg at the first,third and fifth month after surgery was 193.40（44.53,2829.00）ng/m L,192.10（25.58,1758.00）ng/m L and 136.25（16.57,1553.25）ng/m L,respectively.Serum Tg decreased significantly at the first,third and fifth month compared to preoperative Tg（Z=-3.881,-4.587,-4.823,P<0.001）.Moreover,there was a large variation in serum Tg between the first and third month as well as the third and fifth month（Z=-3.661,-3.931,P<0.001）.3.The pain score of 36 patients before ¹²⁵I seed implantation was 5.00（4.00,6.00）,and the pain score at the first,third,and fifth month was 3.00（2.25,4.00）,2.00（2.00,3.00）,and 2.00（1.00,3.00）,respectively.The pain score at the first,third,and fifth month after therapy were considerably lower than before treatment（Z=-5.339,-5.330,-5.278,P<0.001）.The change in pain score between the first and third month,as well as the third and fifth month,was also rather noticeable（Z=-4.914,-4.104,P<0.001）.4.Radiological injury occurred in two patients during follow-up,including one case of radiation dermatitis grade I and one case of radiation pneumonia grade I.Two patients suffered puncture-related complications,including one case of bleeding and one case of pneumothorax.Three patients experienced mild myelosuppression and five patients got radioactive seeds migration.Conclusion:1.¹²⁵I seed implantation in the treatment of refractory differentiated thyroid cancer shows good local control effect,considerable drop in serum Tg,significant pain relief and substantial improvement in patient’s well-being.2.Treatment-related complications are infrequent with ¹²⁵I seed implantation,which is a straightforward,secure,and practical method for treating refractory differentiated thyroid cancer.