Cumulative doses of adjunct 131I treatment depend on location of residual thyroid tissue after total thyroidectomy in differentiated thyroid cancer

PurposeThe aim of this study was to review the outcome after adjunct postoperative 131I therapy in patients with differentiated thyroid carcinoma (DTC) treated with total thyroidectomy (excluding medullary thyroid carcinoma).MethodsRetrospective chart review: Management protocol is total thyroidectomy with cervical node sampling, 131I whole-body scan 3 weeks postoperatively to document residual thyroid tissue or metastasic lesions. Adjunct treatment consists of one or more 131I (100-200 mci/1.73 m2). Patients are considered disease free if 2 consecutive 131I whole-body scan are negative with undetectable thyroglobulin level.ResultsTwenty-one patients, 14 females and 7 males, with a mean age of 13.6 years were treated. Whole-body scan postoperatively revealed uptake in the thyroid bed (TB) in 10 patients, in cervical lymph nodes (CLN) in 9 patients, and in CLN and lungs in 2 patients. Patients with residual uptake in TB received a significantly lesser dose of 131I (mean, 122 ± 53 mci) than those with metastasic CLN (357 ± 182 mci) (P < .004) (t test) or lung mets (523.5 mci). With a mean follow-up of 7.8 years (range, 1-16 years), overall survival is 100% but disease-free survival is 100%, 66%, and 0% respectively for patients with residual disease in TB, CLN, and lungs.ConclusionPatient with residual thyroid tissue in the TB required a significantly lesser number of treatments and doses of 131I compared to patients with cervical node metastases with a 100% disease-free survival. The best management of immediate postoperative residual cervical nodes (surgical excision vs 131I) remains to be defined. The efficacy of 131I therapy in patients with lung metastases remains controversial with complete remission unlikely.