The clinical significance of persistently high or rising anti-thyroglobulin antibodies on follow-up of patients with differentiated thyroid carcinoma

Objectives We aimed to investigate the added value of presence of high serum anti-thyroglobulin antibody levels in the postoperative work-up of patients with differentiated thyroid cancer (DTC).

Methods 582 patients who had undergone bilateral total thyroidectomy and radioiodine remnant ablation therapy for DTC, were referred for routine follow-up. Among these, 86 patients with elevated serum TgAb levels (>100IU/ml) were enrolled and clinical significance was evaluated.

Results Average TgAb levels were 486IU/ml (range: 105-2070IU/ml) in whole patient group. Of 86 patients, 80 had elevated TgAb levels at the time of post-operative, preablation evaluation and 6 had rising TgAb levels on follow-up. In 53 of 80 patients, serum TgAb levels were decreased (<20IU/ml) without recurrence on follow-up and in 27, TgAb levels remained persistently high or increased. When evaluated for etiology, 11 had either cervical/mediastinal lymph node metastasis or distant disease at the time of first ablative dose of radioiodine, 6 developed cervical lymphatic metastasis on follow-up, 1 with previous cervical nodal metastasis on diagnosis progressed with lung metastasis, whereas no histopathological confirmation of disease could be established in 9. In the assessment of 6 patients with rising TgAb levels on follow-up, 5 had locoregional disease at the time of initial diagnosis and had progressive disease on follow-up; however, no site of disease was detected in 1 with rising TgAb. The frequency of lymphatic metastasis in initial diagnosis was significantly higher in patients with persistently high or increasing TgAb levels compared to patients with decreasing levels in further follow-up (p=0.02).

Conclusions Persistently high TgAb levels as well as rising TgAb levels on follow-up may predict persistent disease in DTC. Thus, we consider that, similar to Tg levels, patients with elevated TgAb levels should also be closely monitored for recurrent or metastatic disease.