ISSN : 2146-3123
E-ISSN : 2146-3131

Evaluation of Discordance in Differentiated Thyroid Cancer Patients with Negative Radioiodine Scans and Positive Thyroglobulin Values at the Ablation Outcome Control
Zeynep Gözde Özkan 1, Işık Adalet 1, Cüneyt Türkmen 1, Halim İşsever 2, Yeşim Erbil 3, Harika Boztepe 4, Neşe Çolak 4, Ferihan Aral 4
1Department of Nuclear Medicine, İstanbul Faculty of Medicine, İstanbul University, İstanbul, Turkey
2Department of Public Health, İstanbul Faculty of Medicine, İstanbul University, İstanbul, Turkey
3Department of General Surgery, İstanbul Faculty of Medicine, İstanbul University, İstanbul, Turkey
4Department of Endocrinology and Metabolic Diseases, İstanbul Faculty of Medicine, İstanbul University, İstanbul, Turkey
DOI : 10.5152/balkanmedj.2011.004
Pages : 43-48

Abstract

Objective: We aimed to evaluate the discordance of 5 mCi (185 MBq) I-131 whole body scan (WBS) and thyroglobulin (Tg) values at the ablation outcome control in differentiated thyroid cancer (DTC) patients who had thyroidectomy and then received radioiodine (RAI) ablation.

Materials and Methods: We retrospectively evaluated 36 DTC patients who had RAI treatment in our department between 1992-2009 and whose 5 mCi (185 MBq) I-131 WBS were negative, but Tg values were ≥2 ng/ml during the ablation outcome control (Patient group). Thirty-six patients whose Tg values were < 2 ng/ml and showed no discordance at the same control made up the control group. Patient and control groups were compared in terms of age, gender, histopathological features, ablation dose, Tg value before ablation, and 24. hour RAI uptake value during ablation. The patient group was then evaluated for the cause of the discordance.

Results: There were 28 female and 8 male patients whose mean age was 45.6±11.39 in patient group. In the control group, there were 29 female and 7 male patients whose mean age was 41.5±11.69. According to the reason of discordance at the ablation outcome control, the patient group was divided into 2 groups: 15 (42%) patients (9 female, 6 male patients, mean age: 50.66±10.73) who had metastatic lymph nodes as the reason of discordance constituted the lymph node group. The remaining 21 (58%) patients (19 female, 2 male patients, mean age: 41.5±10.44) were the micrometastatic group in which the cause of discordance could not be determined. There were statistically significant differences in soft tissue invasion (p<0.003), Tg levels before RAI treatment (p<0.002), and diameter of tumor >2 cm (p<0.035) between patient and control groups. Among the patient group, male gender (p<0.03), diameter of tumor >2 cm (p<0.05), thyroid capsule invasion (p<0.03), and age>40 (p<0.01) were significantly different between lymph node and micrometastatic groups.

Conclusion: I-131 WBS/Tg level discordance at the ablation outcome control is mainly caused by metastatic lymph nodes.

Keywords : Differentiated thyroid carcinoma, radioiodine ablation, I-131 whole body scan, lymph node metastases
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