131-I treatment of micronodular pulmonary metastases from papillary thyroid carcinoma

Pulmonary metastases from papillary thyroid carcinoma shorten the survival of the hosts. Treatments with 131-I have been reported to induce disappearance of these tumors in a large proportion of afflicted patients. In this study, consecutive patients with diffuse micronodular lung metastases from papillary thyroid carcinoma were examined to determine if disappearance of tumor occurred, and how much disappeared, after substantial amounts of 131-I were administered.

Of 232 patients treated with 131-I for thyroid carcinoma between 1985 and 1994, 12 patients between the ages of 5 and 45 years exhibited evidence of micronodular metastases to the lungs that concentrated 131-I. Each patient had undergone total or nearly total thyroidectomy and cervical lymph node dissection. All neoplasms were well differentiated papillary carcinoma, but one also had focal, poorly differentiated insular components. Follicle formation by tumors varied from less than 10% to 100% of the histologic sections. Effects of treatment were measured by three indices: chest X-ray and/or CT images, scintigraphic images, and serum thyroglobulin levels. Individual activities of 131-I ranged from 2.2 gigabequerel (GBq) (initial activity in the 5-year-old patient) to 13 GBq, and were greater than 7.4 GBq in 6 patients. Only one treatment was given to three patients, two were given to seven, and more than two were given to two. The duration of follow-up was at least one year.

In two patients, the only evidence of lung metastases was on scintigraphic images made a few days after treatment. Another patient had a normal X-ray but showed diffuse uptake of 131-I in the lungs on a diagnostic scintiscan. Of the nine patients with abnormal X-ray and CT images, seven showed improvement, but tumors disappeared in only two. In the ten patients with abnormalities on the diagnostic scintiscans, five eventually manifested no abnormality. At the outset, thyroglobulin levels exceeded 10 ng/mL in each patient; 3 individuals exhibited a decline in level by 25% or more, and a value of less than 6 ng/mL, uncomplicated by thyroglobulin antibodies, was seen in two patients. Only two patients attained normality in all three indices. Hematologic toxicity was modest and reversible.

Despite a number of previous reports that pulmonary metastases from thyroid carcinoma disappear in approximately half of patients treated with 131-I, evidence of tumor reduction was found in most, but a complete remission occurred in only 2 of 12 patients. Nevertheless, 131-I therapy may be useful to decrease the tumor burden in many such patients.