Abstract: Objective · To investigate the curative efficacy and influential factors of 131I treatment for pulmonary metastases differentiated thyroid carcinoma (DTC). Methods · A total of 95 DTC patients (33 males and 62 females) with pulmonary metastasis who underwent 131I treatment in Department of Nuclear Medicine, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, April 2012 to May 2016 were retrospectively analyzed. The efficacy of 131I treatment was assessed using determination of serum thyroglobulin level and 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (18F-FDG PET/CT). The possible factors affecting efficacy included gender, age, pathological classification, wheteer pulmonary metastasis diagnosed before treatment, the iodine and 18F-FDG uptake of pulmonary lesions, the size and number of lung lesions, extrapulmonary distant metastasis. Univariate analysis was performed using Rank test and χ2 test, the critical value was obtained through receiver operating characteristic (ROC) curve and Logistic regression was also performed. Results · The rates of efficacy and inefficacy of 131I treatment were 53.68% and 46.32%, respectively. Univariate analyses showed that maximum standardized uptake value (SUVmax) evaluated18F-FDG PET/CT (P0.004), the size of lung metastases (P0.000), age<45 years (P0.004), 131I uptake (P0.022), whether pulmonary metastasis diagnosed before treatment (P0.000), extrapulmonary distant metastasis (P0.014) were the factors influencing outcome of 131I treatment. The critical value of 18F-FDG uptake for patients obtainedROC curve was 1.45 (sensitivity of 56.8% and specificity of 76.5%) and the critical value of lung lesion diameter was 9.63 mm (sensitivity of 43.2% and specificity of 88.2%). Multivariate Logistic regression analysis showed that the influential factors included the age of patients, the size and 18F-FDG SUVmax of lung metastases and whether pulmonary metastasis diagnosed before treatment. Conclusion · 131I treatment is an effective method for pulmonary metastases DTC. The patients aged less than 45 years, with the lung lesion size less than 9.63 cm, low 18F-FDG SUVmax and diagnosed before treatment may have good response to 131I treatment. [Key words]thyroid neoplasm; neoplasm metastasis; lung; radiotherapy; iodine radioisotope

Key words: thyroid neoplasm, neoplasm metastasis, lung, radiotherapy, iodine radioisotope