Serum thyroglobulin concentration in post- operative differentiated thyroid cancer patients with metastasis treated by iodine-131

Serum thyroglobulin is a valuable tumor marker in post-operative differentiated thyroid cancer (DTC) patients with metastasis after iodine-131 remnant thyroid ablation. Aim: the purpose of our study was to determine the value of serum thyroglobulin concentration in DTC patients with metastasis after iodine-131 remnant thyroid ablation. Materials and methods: 504 post-operative DTC patients were divided in to metastatic and non-metastatic groups. All the patients were received periodic 131I treatment and undergo follow - up in Department of Nuclear Medicine, Tran Hung Dao Hospital. The patients underwent clinical examinations, serum thyroglobulin (Tg) and anti-Tg antibody measurements, conventional chest X-rays, 131I whole-body scan. Results: 71.1% of non-metastatic DTC patients had Tg level < 10 ng/ml in comparison with 28.9% of metastatic DTC patients (p < 0.05). 26.4% of patients with Tg level < 10 ng/ml represented metastases on 131I whole-body scan, 13.1% of DTC patients had Tg level ≥ 10 ng/ml but no evidence of metastases detected on clinical examination and 131I whole-body scans. Mean Tg level in the DTC patients with metastasis was higher than that of the non-metastatic DTC patients (p < 0.001). Also, mean Tg levels in the DTC patients with lung metastatic X-ray - positive findings and multiple-site metastasis were greater than those of the DTC patients with lung metastatic X-ray-negative and cervical lymph node metastasis, respectively (p < 0.01). Conclusions: serum Tg concentration is complementary valuable measurement for diagnosis, follow-up of recurrences and metastatic extent evaluation in the post-operative DTC patients with metastasis after iodine-131 remnant thyroid ablation. 131I whole-body scan and diagnostic multiple modality should be used in case of false - negative or false - positive serum Tg concentration results. (author)