Diagnostic 131I whole body scanning after thyroidectomy and ablation for differentiated thyroid cancer

OBJECTIVE: To assess the value of the diagnostic whole body (131)I scan after thyroidectomy and (131)I ablation. DESIGN: Retrospective analysis of all patients with differentiated thyroid cancer treated in one centre between 1990 and 2000. RESULTS: A total of 153 consecutive patients who underwent diagnostic scanning following ablative therapy were identified. This diagnostic scan was positive in 20 patients (13%) and faintly positive in 16 patients (11%). The majority (117 patients) had negative scans. Of the 20 patients with positive scans, four received no further treatment, nine showed no abnormal uptake following a second ablative (131)I dose and seven had uptake in the thyroid bed (six) or in neck nodes (one) after repeat ablation. OUTCOME: In the group with positive scans, the four patients who received no further treatment and the nine with a negative second ablation scan remained disease free during follow-up. No patient with a positive diagnostic scan received additional (131)I therapy which would not otherwise have been given based on the clinical findings, serum thyroglobulin (Tg) values or the presence of anti-Tg antibodies. Ten of the patients with negative scans developed recurrent disease which was always detected clinically or by a rising serum Tg value. CONCLUSIONS: Diagnostic whole body (131)I scans add little extra information and in our experience do not influence patient management. They should be reserved for patients in whom serum Tg levels are unreliable because of the presence of antibodies or when there is clinical suspicion of tumour.