[Usefulness of radioiodine scanning in patients with moderate/high risk differentiated thyroid carcinoma in whom thyroglobulin after thyroxin withdrawal is undetectable after initial treatment]

Abstract

We selected 92 patients without antithyroglobulin antibodies (TgAb), in whom thyroglobulin (Tg) after L-thyroxin withdrawal was undetectable (<1 ng/ml) 6-12 months after initial therapy and who were considered to be at moderate / high risk for recurrence by this criteria: age >45 years; tumor size >1.5 cm; and lymph nodes metastases in 43 (46.7%), local invasion in 26 (28.2%) or distant metastases in 23 (25%). Control whole-body scanning was negative in 78.2% of the cases and showed cervical uptake in the others. Cases presenting thyroid bed uptake in the absence of tumor recurrence did not receive radioiodine and Tg remained undetectable one year after the initial evaluation in all. Cervical uptake was not observed in 4/13 cases on repeated scan. In contrast, even in the absence of uptake and with undetectable Tg, 7 patients with recurrence confirmed by ultrasound (US) received surgical treatment. US showed 92.8% sensitivity for the detection of local-regional disease. The present study suggests that even moderate/high-risk patients without TgAb and with undetectable Tg levels (off T4) do not require radioiodine scanning after initial treatment and can be evaluated by cervical US.