Background: The accuracy of thyroglobulin (Tg) as a tumour marker following lobectomy for differentiated thyroid cancer (DTC) remains controversial. A Tg (<10 µg/l) looked promising in identifying those without clinically apparent recurrence after median 51 months of follow-up. Longer term follow up allows assessment of the diagnostic utility of thyroglobulin in predicting relapse.
Methods: Ninety-nine patients who underwent lobectomy for DTC were retrospectively analyzed using hospital electronic records. Thyroid function and Tg levels were only available for the last ten years.
Results: The mean patient age was 65±12 years (2/3 were women). Median follow-up was 23 years (IQR 1231 years). Seven died due to non-thyroid related issues. Four patients required further intervention, three had completion thyroidectomy (two for recurrence in contralateral lobe and one for benign nodule) and one had lymph node dissection (further clinical details unknown). Using a Tg cut off <10 ug/dl to predict long-term relapse gave a sensitivity 50%, specificity of 89.5%, positive predictive value 16. 6% and a negative predictive value 97.7% (Table 1).
|Case 1||Case 2||Case 3|
|Initial surgery||Left lobectomy||Right lobectomy||Right lobectomy|
|Tg (µg/dl) at completion thyroidectomy||34||5||21|
|Thyroid enlargement||Not present||Present||Not present*|
|Subsequent pathology||Colloid degeneration||PTC||Micro-PTC|
|Ψ-Papillary thyroid cancer, ¶-Follicular thyroid cancer, *-USG showed nodule of 8 mm.|
Conclusion: Serum Tg was elevated in two patients who underwent completion thyroidectomy following lobectomy for DTC but a cut-off of 10 µg/l didnt differentiate recurrent PTC from benign nodularity. One case with recurrent PTC had Tg <10 µg/dl. The high negative predictive value (NPV) of Tg <10 µg/dl for recurrence suggests some benefit in long-term follow-up after lobectomy for DTC, but its low sensitivity limits its clinical utility. Clinical± radiological surveillance remains useful for these patients.