In this study, 27 patients less than 18 yr old with pulmonary metastases from well-differentiated thyroid carcinoma were evaluated to determine their response to (131)I therapy.
Methods: Of 121 children and adolescents treated with (131)I between 1963 and 1996, 27 patients had pulmonary metastases associated with nodal disease. Treatment response from (131)I was measured by three parameters: chest radiograph, scintigraphic images and serum thyroglobulin levels. Total activity of (131)I administered ranged from 4.6 GBq (125 mCi) to 38.7 GBq (1.05 Ci). Four patients were given one treatment, 8 were given two treatments, 4 were given three treatments and 11 were given more than three treatments. Radiation doses to the lungs were estimated in 14 patients using the MIRD methodology. The minimum duration of follow-up was 6 mo.
Results: At the time of initial presentation, diagnostic (131)I studies revealed bilateral radioiodine uptake in the lungs in 19 (70.4%) patients, whereas 12 (44.4%) patients had abnormal chest radiographs. One patient was lost to follow-up and was excluded from the study. Of the 26 patients studied, complete ablation of pulmonary metastases was observed in 8 (30.8%), partial ablation in 17 (65.4%) and there was no response to treatment in 1 (3.8%). Dosimetric parameters such as radioiodine uptake as a percentage of therapeutic activity, effective half-life and radiation dose delivered to the lungs were evaluated with each therapy. There was a progressive decline in each of these parameters with successive therapies. No correlation was observed between the radiation dose delivered and the response of pulmonary metastases to therapy. The number of therapies and amount of radioiodine administered had no influence on the ablation response. Of the 26 patients, 13 had a follow-up duration of less than 5 yr, 7 had 5-10 yr and 6 had more than 10 yr. One patient developed new metastases after 7 yr of diagnosis and treatment. One patient died of the disease after 4 yr. All surviving patients were asymptomatic and leading normal lives.
Conclusion: Complete response of pulmonary metastases after (131)I therapy is difficult to achieve. A partial response with reduction of metastatic disease is possible and, in general, the patients had a good quality of life with no further disease progression and a low mortality rate.