Radioactive iodine treatment and external radiotherapy for lung and bone metastases from thyroid carcinoma

We assessed the therapeutic benefits of 131I treatment in patients with distant metastases of differentiated thyroid carcinoma.

Of 2200 patients treated for differentiated thyroid carcinoma at our institution, 394 had lung and/or bone metastases.

Two-thirds of the patients had 131I uptake in their metastases, but only 46% achieved a complete response. Prognostic factors for complete response were: younger age, presence of 131I uptake in the metastases and small extent of disease. The survival rate was 33% at 15 yr. As shown by multivariate analysis, favorable prognostic factors for survival were: younger age and time of metastases detection, well-differentiated histologic type of the thyroid tumor, presence of 131I type uptake in the metastases, small extent of the disease and year of discovery of metastases.

In terms of survival, the benefits of 131I therapy cannot be demonstrated by prospective controlled studies. The present study clearly demonstrates, however, that treatment with 131I is one of the factors which accounts for survival; patients whose metastases concentrated 131I and who could be treated with radioiodine had higher survival rates. Patients who achieved complete response following treatment of distant metastases had a 15-yr survival rate of 89%, while those who did not achieve complete response had a survival rate of only 8%. The survival rate improved with the year of discovery of distant metastases, after 131I total-body imaging and serum thyroglobulin measurements were routinely used.