Graves' disease and radioiodine therapy

Summary

Aim: This study was performed to determine the results of ablative radioiodine therapy (RIT) when the achieved dose in the thyroid was above 200 Gy and to characterize predictive factors for treatment outcome. Patients, methods: A total of 571 consecutive patients were observed for 12 months between July 2001 and June 2004. Inclusion criteria were a confirmed diagnosis Graves' disease, compensation of hyperthyroidism and withdrawal of antithyroid drugs two days before preliminary radioiodine-testing and RIT. The intended dose was 250 Gy and the therapeutically achieved dose was calculated from serial uptake measurements. The end-point measure was thyroid function 12 months after RIT; success was defined as elimination of hyperthyroidism. The relation between success rate and the achieved dose, thyroid volume, age and sex of patients, TSH- and TRAb-values and presence of ophthalmopathy was analysed. Results: Relief from hyperthyroidism was achieved in 96% of patients who received more than 200 Gy, even for thyroid volumes >40 ml. The success of ablative RIT was not influenced by age or sex of patients, or by TSH- or TRAb values or concomitant ophthalmopathy. The mean achieved dose in the thyroid was 298 Gy with a standard deviation of 74.6 Gy. Conclusion: To achieve a dose of over 200 Gy with the above standard deviation, we recommend calculating an intended dose of 250 Gy and using a dosimetric approach with early and late uptake values in the radioiodine test, to allow early therapeutic intervention should the posttherapeutic thyroid dose fall unexpectedly below 200 Gy.

Zusammenfassung

Ziel der Studie war die Überprüfung der Dosisabhängigkeit oberhalb von 200 Gy und möglicher Einflussfaktoren auf den Erfolg der ablativen Radioiodtherapie (RIT) des Morbus Basedow. Patienten, Methodik: Von Juli 2001 bis Juni 2004 konnten 571 Patienten 12 Monate nach Radioiodtherapie beobachtet werden. Einschlusskriterien waren ein gesicherter Morbus Basedow, eine Rekompensation der Stoffwechsellage und ein Absetzen der thyreostatischen Medikation zwei Tage vor dem Radioiodtest und der RIT. Die Zieldosis war 250 Gy. Peritherapeutisch wurde die tatsächlich an der Schilddrüse erreichte Dosis durch serielle Uptake-Messungen bestimmt. Endpunkt der Studie war die Schilddrüsenfunktion 12 Monate nach RIT. Als Erfolg wurde die Beseitigung der Hyperthyreose gewertet. Die Erfolgsrate wurde verglichen mit der an der Schilddrüse erreichten Dosis, dem Schilddrüsenvolumen, dem Alter und Geschlecht , dem TSH- und TRAK-Wert sowie dem Vorliegen einer endokrinen Orbitopathie. Ergebnisse: Ab einer an der Schilddrüse erreichten Dosis von 200 Gy betrug der Therapieerfolg 96%. Dies galt auch für Schilddrüsenvolumina >40 ml. Alter und Geschlecht, TSH- und TRAK-Wert sowie eine endokrine Orbitopathie blieben ohne Einfluss auf den Therapieerfolg. Die durchschnittlich an der Schilddrüse erreichte Dosis betrug 298 Gy bei einer Standardabweichung von 74,6 Gy. Schlussfolgerung: Um bei o. g. Standardabweichung bei allen Patienten sicher über 200 Gy zu erreichen, wird bei peritherapeutischer Dosimetrie mit der Möglichkeit einer Nachtherapie eine Zieldosis im Radioiodtest von 250 Gy empfohlen.

Keywords

Radioiodine therapy - Graves' disease - hyperthyroidism - dosimetry

Schlüsselwörter

Radioiodtherapie - Morbus Basedow - Hyperthyreose - Dosimetrie

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