PULMONARY METASTASES IN CHILDREN AND ADOLESCENTS WITH WELL-DIFFERENTIATED THYROID-CANCER

In this study, 27 patients less than 18 yr old with pulmonary metastas es from well-differentiated thyroid carcinoma were evaluated to determ ine their response to I-131 therapy. Methods: Or 121 children and adol escents treated with I-131 between 1963 and 1996, 27 patients had pulm onary metastases associated with nodal disease. Treatment response fro m I-131 was measured by three parameters: chest radiograph, scintigrap hic images and serum thyroglobulin levels. Total activity of I-131 adm inistered ranged from 4.6 GBq (125 mCi) to 38.7 GBq (1.05 Ci). Four pa tients were given one treatment, 8 were given two treatments, 4 were g iven three treatments and 11 were given more than three treatments. Ra diation doses to the lungs were estimated in 14 patients using the MIR D methodology. The minimum duration of follow-up was 6 mo. Results: At the time of initial presentation, diagnostic I-131 studies revealed b ilateral radioiodine uptake in the lungs in 19 (70.4%) patients, where as 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 t reatment in 1 (3.8%). Dosimetric parameters such as radioiodine uptake as a percentage of therapeutic activity, effective half-life and radi ation dose delivered to the lungs were evaluated with each therapy. Th ere was a progressive decline in each of these parameters with success ive therapies. No correlation was observed between the radiation dose delivered and the response of pulmonary metastases to therapy. The num ber of therapies and amount of radioiodine administered had no influen ce on the ablation response. Of the 26 patients, 13 had a follow-up du ration 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 treatmen t, One patient died of the disease after 4 yr. All surviving patients were asymptomatic and leading normal lives. Conclusion: Complete respo nse of pulmonary metastases after I-131 therapy is difficult to achiev e. A partial response with reduction of metastatic disease is possible and, in general, the patients had a good quality of life with no furt her disease progression and a low mortality rate.