Rate of elimination of radioiodineavid lymph node metastases of differentiated thyroid carcinoma by postsurgical radioiodine ablation

Summary

SPECT/CT detects radioiodine-positive cervical lymph node metastases (LNMs) of differentiated thyroid carcinoma (DTC) at the time of postsurgical radioablation (RA). Preliminary evidence indicates that the majority of LNMs are successfully treated by RA. The aim of this study was to confirm this evidence in a bicentric setting and to evaluate whether size is a predictor for successful elimination. Patients and methods: Since 01/2007 and 05/2008, respectively, SPECT/spiral-CT is performed routinely in all patients with DTC at RA in two University Clinics. The outcome of iodine-positive LNMs identified by SPECT/CT until 12/2012 was analyzed by follow-up diagnostic ¹³¹I scans and serum thyreoglobulin (Tg) values. LNM volume and short-axis diameter were evaluated as prognostic factors by a receiver-operating characteristic (ROC) analysis. Results: 79 patients with 97 iodine-positive LNMs were included. Surgery was carried out in 8 patients with 13 LNMs due to the presence of additional iodine-negative lesions. Of the remaining 84 LNMs, 74 (88%) were successfully treated as demonstrated by radioiodine scans at follow-up. 10 LNMs persisted. 67/70 LNMs smaller than 0.9 ml were treated successfully, whereas this was the case of only 6/14 exceeding this threshold. Using this cut-off level to predict treatment success, sensitivity, specificity, positive and negative predictive value were 92%, 73%, 96%, and 57%. Results for short-axis diameter (cut-off level < 1cm) were 90%, 69%, 94% and 56%. Conclusion: RA is effective in the treatment of the majority of ¹³¹I-positive LNMs identified in SPECT/CT images. In this study, 88% of iodine-positive LNM in DTC were successfully treated by radioiodine given at RA. Both LNM volume and diameter are reliable predictors of treatment success.

Zusammenfassung

Nach Ablation des post-operativen Schilddrüsengewebes mit Radioiod (RA) dient die SPECT/ CT bei Patienten mit differenzierten Schilddrüsenkarzinomen (DSDK) zur Identifikation Radioiod-positiver, zervikaler Lymphknotenmetastasen (LKM). Bisherige Ergebnisse zeigen, dass die meisten LKM im Rahmen der RA erfolgreich therapiert werden. Ziel der Studie war eine Bestätigung dieser Ergebnisse in einer bizentrischen Analyse und Evaluation der Lymphknotengröße als Prädiktor für den Therapieerfolg. Patienten und Methoden: Seit 01/2007 bzw. 05/2008 wird die SPECT/spiral-CT in zwei Universitätskliniken routinemäßig eingesetzt. Bis 12/2012 in der SPECT/CT identifizierte, Radioiod-positive LKM wurden im Rahmen der Nachsorge mittels ¹³¹I Aufnahmen und Serum-Thyreoglobulinwerten (Tg) kontrolliert. Durch Receiver-Operating-Characteristic(ROC)-Analysen wurden das LKM-Volumen und der Kurzachsendurchmesser als Prädiktoren für eine erfolgreiche Therapie evaluiert. Ergebnisse: 79 Patienten mit 97 Radioiod-positiven LKM wurden eingeschlossen. 8 Patienten mit insgesamt 13 LKM wurden bei zusätzlichen, Radioiod-negativen Metastasen operiert. 74 der übrigen 84 LKM (88%) wurden erfolgreich therapiert, wie sich in ¹³¹I-Aufnahmen in der Nachsorge zeigte. 10 LKM blieben weiterhin nachweisbar. 67 von 70 LKM mit einem Volumen kleiner als 0,9 ml wurden erfolgreich therapiert, wohingegen nur 6 von 14 LKM mit einem Volumen größer als 0,9 ml erfolgreich therapiert wurden. Die Sensitivität und Spezifität sowie der positive und negative prädiktive Wert zur Prädiktion des Therapieerfolges unter Verwendung dieses Cut-off-Wertes lagen bei 92% und 73% bzw. 96% und 57%. Die Ergebnisse des Kurzachsendurchmessers mit einem Cut-off-Wert von kleiner 1,0 cm ergaben 90%, 69%, 94% und 56%. Schlussfolgerung: Durch die RA wird die Mehrzahl von ¹³¹I-positiven LKM erfolgreich therapiert. In dieser Studie wurden 88% von Radioiod-positiven Lymphknoten bei Patienten mit DSDK im Rahmen der RA erfolgreich therapiert. Das LKM-Volumen und der Kurzachsendurchmesser stellen verlässliche Prädiktoren des Therapie erfolges dar.

Keywords

Differentiated thyroid carcinoma - radioiodine - remnant ablation - lymph node metastases - elimination

Schlüsselwörter

Differenziertes Schilddrüsenkarzinom - Radioiod - Restgewebe-Ablation - Lymphknoten-Metastasierung - Beseitigung

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