Abstract: Objective　To explore the clinical features of pulmonary metastasis of differentiated thyroid cancer (DTC) in children and the therapeutic effect of 131I. Methods　The clinical data of pulmonary metastasis of DTC in 14 patients who were ≤18 years old at the time of initial 131I treatment were retrospectively analyzed. Results　In 14 children (5 males and 9 females) an average age was (12.71±3.05) years. All the children were received 131I treatment after total or subtotal thyroidectomy and 131I treatment was received 4 times averagely and a median cumulative dose was 9.43 (8.25 - 19.74) GBq. After treatment, lesions were completely eliminated in 4 cases (28.6%), improved or stabilized in 8 cases (57.1%) and ineffective or progressive in 2 cases (14.3%). The effective rate was 85.7% (12/14). The median follow-up time was 63.4 months (6 - 124 months), with a survival rate of 100%. The median progression free survival time was 63.5 months. The 2-year progression free survival rate was 84.61% and the 5-year progression free survival rate was 80.0%. Conclusion　The incidence of lung metastasis of DTC is high in children, and 131I treatment is effective.

Key words: differentiated thyroid cancer;　radiotherapy;　iodine radioisotopes;　child