Determinanten des Therapieerfolgs bei Radiojodtherapie der multifokalen und disseminierten Autonomie der Schilddrüse

Summary Introduction: Radioiodine therapy is an established treatment option for benign thyroid diseases since the 1950s. However, not all factors influencing the success and outcome of this therapeutic measure have been clarified, yet. The aim of this study was to identify and describe the underlying determinants of success and outcome in patients with multifocal and disseminated autonomy. Material/Methods: Data from 131 consecutive patients treated in the Clinic for Nuclear Medicine at the University Hospital Marburg were collected from 2001 to 2016 due to multifocal or disseminated autonomy. Before therapy, gender, patient age, thyroid volume, current thyroidmedication, thyroid hormone fT3, fT4 and TSH, values of the radioiodine uptake test after 24 hours, of the technetium uptake test after 20 minutes, the administered 131I activity and achieved focal dose were recorded. Six months after therapy, the abovementioned thyroid hormones, drugs, thyroid volume and measured values of the technetium uptake test were measured and documented again. A classification according to the therapeutic outcome (hypo-, eu- and hyperthyroidism) was performed, whereby hypo- and euthyroidism were evaluated as therapy success. The factors influencing outcome and success were analyzed by using the Kruskall-Wallis-test, Mann-Whitney-U-test and logistic regression. Results: Patients received, after calculation of activity by the Hänscheid-Bockisch formula, 286 to 2075 megabecquerel with an averagelesion dose of 351.37 Gray. Of the therapies were 93.13% successfully completed, thereof 22.13% with hypothyroid outcome. An association between increased pretherapeutic fT4 levels and hypothyroid outcome was demonstrated. In addition, this study confirmed that low 131I activity is more related to lead to a hyperthyroid outcome. Finally, there is a correlation between a low RIU and a hypothyroid outcome. Conclusion: The results underline the relevance of the pre-therapeutic euthyroid metabolism for the success of therapy. An optimal adjustment of the endocrine function of the thyroid gland prior to therapy is therefore an important determinant of therapeutic success. In addition, the 131I dose to be administered should be questioned on the basis of the calculated RIU and the number of measurements and their timing after the administered 131I bolus should be further investigated to improve the informative value of the RIU. On the basis of these results, the relevance of the pre-therapeutic metabolic adjustment as a direct influencing factor on the RIU should be emphasized. This study demonstrates the endocrine function of the thyroid gland prior to radioiodine therapy as a determinant for its therapeutic success. Accordingly, the outcome of radioiodine therapy could be improved in the future by optimizing this determinant.