Beschreibung:
<jats:title>Summary</jats:title><jats:p><jats:bold>Objective </jats:bold> To evaluate the relationships between thyroid remnant <jats:sup>131</jats:sup>I uptake, radiation thyroiditis and remnant ablation success rate between lower (1110 MBq) and higher (3700 MBq) initial ablative <jats:sup>131</jats:sup>I dose for post‐surgical ablation therapy for differentiated thyroid cancer.</jats:p><jats:p><jats:bold>Design </jats:bold> Patients having post‐surgical administration of 1110 MBq (68 patients) or 3700 MBq (115 patients) <jats:sup>131</jats:sup>I were retrospectively reviewed. Thyroid remnant <jats:sup>131</jats:sup>I uptake on a 48 h post‐administration scan was correlated with neck symptoms experienced. Patients were classified as having insignificant, mild or severe thyroiditis based on symptoms. Absent thyroid bed <jats:sup>131</jats:sup>I uptake on a follow‐up 74 MBq <jats:sup>131</jats:sup>I study was considered successful ablation.</jats:p><jats:p><jats:bold>Results </jats:bold> 183 patients were included. Median <jats:sup>131</jats:sup>I remnant uptake was 37 MBq. 21% (39/183) of patients developed thyroiditis. Incidence and severity of thyroiditis increased with increasing remnant <jats:sup>131</jats:sup>I activity (<jats:italic>P</jats:italic> ≤ 0·0001). Risk of thyroiditis increased by 64% for every 37 MBq increase in remnant <jats:sup>131</jats:sup>I uptake. OR = 1·64 [1·36–1·99]. Severe thyoriditis was only seen with remnant <jats:sup>131</jats:sup>I uptake > 73 MBq. For patients treated with 1110 MBq and 3700 MBq, incidence of thyroiditis was 12% and 27% (<jats:italic>P =</jats:italic> 0·02) and remnant ablation success rate was 76% and 84% (<jats:italic>P =</jats:italic> NS), respectively. Occurrence of thyroiditis did not correlate with successful ablation.</jats:p><jats:p><jats:bold>Conclusions </jats:bold> Incidence and severity of radiation thyroiditis following <jats:sup>131</jats:sup>I remnant ablation therapy is directly related to thyroid remnant <jats:sup>131</jats:sup>I uptake. As 1110 MBq <jats:sup>131</jats:sup>I is associated with a significantly lower frequency of thyroiditis but similar remnant ablation rate to 3700 MBq, it warrants consideration for thyroid remnant ablation particularly in patients with low risk disease.</jats:p>