Failure of low doses of 131I to ablate residual thyroid tissue following surgery for thyroid cancer.

Thirteen patients received an initial dose of 25-29.9 mCi (9259-1, 106 MB1) of 131I following partial thyroidectomy for papillary, follicular, or mixed carcinoma. Administration of thyroxine (T4) or triiodothyronine (T3) was stopped 3-12 weeks and 1-6 weeks, respectively, before therapy or imaging. Patients remained on normal diets and did not receive thyroid-stimulating hormone (TSH) or diuretics. Follow-up 3 months to 2 years after therapy demonstrated that ablation of thyroid bed activity was successful in only one patient, who still had metastases. This suggests that administration of 25-29.9 mCi of 131I following surgery is unreliable for ablation of residual thyroid bed activity.