Background: Local and regional recurrences occur in up to 20% of patients with papillary and follicular thyroid carcinoma. Diagnostic work-up and treatment modalities are still controversial, because nodal control is difficult to ascertain. We assessed the value of serum thyroglobulin (Tg) determination and of high-dose 131I total body scan (TBS) for ascertaining the absence of disease in patients who had already been treated with radioiodine and who subsequently underwent surgery.
Methods: Between 1990 and 2000, 105 patients who had been treated with radioiodine for lymph node recurrence with initial 131I uptake were included in a standardized protocol performed after withdrawal of thyroid hormone treatment: on day 1, serum Tg determination and administration of 3.7 GBq 131I; on day 4, 131I TBS; on day 5, surgery; on day 8, 131I TBS.
Results: In 25 patients the serum Tg obtained following thyroid hormone withdrawal was undetectable: for these patients, the 131I TBS showed uptake foci in 21 and pathology disclosed neoplastic foci in 19. In 32 patients the serum Tg ranged from 1 to 10 ng/ml: for these patients, the 131I TBS showed uptake foci in 26 and pathology disclosed neoplastic foci in 28. In 48 patients the serum Tg level was above 10 ng/ml: for these patients, the 131I TBS showed uptake foci in 38 and pathology disclosed neoplastic foci in 46. Thus, no uptake was found preoperatively in 20 patients, among whom pathology disclosed lymph node metastases in 16. However, both tests were negative in only two of the 93 patients in whom pathology disclosed neoplastic foci.
Conclusion: Serum Tg levels and 131I TBS cannot be considered as reliable indicators for the absence of disease in patients already treated with 131I. However, when both tests are negative, the risk of persistent disease is minimal.