Endocrine Abstracts

Introduction: In the management of patients with differentiated thyroid carcinoma (DTC), serum thyroglobulin (Tg) levels are often well correlated with whole-body radio-iodine scanning (WBS) results. However, occasionally a mismatched result, increased Tg with negative WBS, is encountered. High doses of radio-iodine (RAI) have been suggested as a therapeutic choice with controversial results. Our aim was to evaluate the therapeutic benefit of this approach.

Method: We studied 32 DTC patients (12M and 20F; mean age: 42.3 yr) with elevated Tg level and negative WBS who had been treated with high-dose RAI. With a mean follow-up of 25.6 months (all follow-ups>11months), serum Tg, anti-Tg and TSH levels, WBS results, clinical, radiographical and pathological findings following treatment were recorded.

Results: The mean pre-therapy serum Tg with the patient off-treatment was 152±119.0 ng/ml. Although there was a mild trend toward the increase in serum Tg level in the first post-treatment year, the difference did not reach statistical significance. 53.8% of patients had foci of radiotracer uptake in the post-treatment scans. At the end of the follow-ups, 22 patients (68.7%) categorized as non-respondent to RAI therapy (any change or elevation in Tg level or radiological and pathological evidences of progression), four patients (12.5%) as partial-respondent (transient reduction but not normalization of serum Tg) and six patients (18.7%) as respondents to RAI therapy (normalization of serum Tg with no other evidences of remnant disease). In nine of these ten partial- and complete-respondents, the reduction or normalization of serum Tg had occurred in the first post-treatment year.

Conclusion: We recommend that in DTC patients with elevated Tg and negative WBS, only one course of RAI therapy should be examined and if satisfactory response (reduction or normalization of serum Tg) was not achieved, repeated RAI therapies are not logical and other therapeutic methods should be applied.