Evaluation of Discordance in Differentiated Thyroid Cancer Patients with Negative Radioiodine Scans and Positive Thyroglobulin Values at the Ablation Outcome Control

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. Turkish Başlık: Diferansiye Tiroid Karsinomlarında Ablasyon Kontrolü Sırasında Ortaya Çıkan 5 Mci İyot-131 Sintigrafisi Negatif, Tiroglobulin Pozitif Uyumsuzluğunun Değerlendirilmesi Anahtar Kelimeler: Diferansiye tiroid karsinomu, radyoaktif iyot tedavisi, I-131 tüm vücut tarama, lenf nodu metastazı Amaç: Diferansiye tiroid karsinomu (DTK) hastalarında, ablasyon kontrolü sırasında ortaya çıkan 5 mCi İyot-131 tüm vücut sintigrafisi ve tiroglobülin değeri uyumsuzluğunu ve bunun olası nedenlerini incelemeyi amaçladık. Hastalar ve Yöntemler: DTK tanılı hastalarda ablasyon kontrolü için yapılan 5 mCi TVS (-) ve Tg değeri ≥2ng/ml olan 36 hasta retrospektif olarak incelendi(hasta grubu). Tg değerleri <2ng/ml olan ve uyumsuzluk bulunmayan 36 hasta ise kontrol grubu olarak alındı. Hasta ve kontrol grubunun karşılaştırılmasında yaş, cinsiyet, histopatoloji, ablasyon dozu, ablasyon öncesi Tg değeri ve 24. saat RAİ uptake değeri kullanıldı. Ayrıca hasta grubu da uyumsuzluk nedeni açısından incelendi. Bulgular: Hasta grubunda 28K, 8E, yaş ort:45.6±11.39 ; kontrol grubunda 29K, 7E , yaş ort:41.5±11.69 idi. Hasta grubunda uyumsuzluk nedenine yönelik yapılan tetkikler sonucunda 15(%42) hastada lenf bezi metastazı saptanırken (lenf nodu grubu), 21(%58) hastada uyumsuzluk nedeni bulunamadı (mikrometastatik grup). Yapılan istatistiksel çalışmada, hasta ve kontrol grupları arasında yumuşak doku invazyonu, ablasyon öncesi Tg değeri ve tümör çapı>2cm açısından anlamlı fark bulundu. Hasta grubundaki değerlendirmede ise, E cinsiyet, tümör çapı>2cm, tiroid kapsül invazyonu ve yaş>40 gibi parametrelerin karşılaştırılmasında lenf nodu ve mikrometastatik grup arasında anlamlı fark bulundu. Sonuç: Ablasyon kontrolü sırasında ortaya çıkan 5 mCi-TVS (-), Tg (+) uyumsuzluğunda tespit edilebilen başlıca neden lenf nodu metastazıdır.

Keywords

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

Evaluation of Discordance in Differentiated Thyroid Cancer Patients with Negative Radioiodine Scans and Positive Thyroglobulin Values at the Ablation Outcome Control

Öz

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