Radioiodine-131 in differentiated thyroid cancer: a retrospective analysis of an uptake-related ablation strategy

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Abstract
In our hospital, a 24-h radioiodine-131 (131I) uptake-related ablation strategy is used in patients with differentiated thyroid cancer to destroy thyroid remnants after primary surgery. In this strategy, low doses of 131I are used, but data in the literature on its efficacy are conflicting. Therefore, we performed the present study to evaluate the clinical outcome of this ablation strategy. In this study, patients (n=235) were selected who underwent thyroidectomy for differentiated thyroid cancer, followed by an ablative dose of 131I. Approximately 6 months after ablation, treatment efficacy was evaluated using radioiodine scintigraphy and thyroglobulin (Tg) measurements. Successful ablation was defined as the absence of radioiodine uptake in the neck region (criterion 1). Tg values were determined 3–12 months after ablation (criterion 2). Based on criterion 1, unsuccessful ablation was found in 43.0% of cases. Pre-treatment uptake values were statistically significantly lower (P=0.003) in successfully ablated patients (mean 5.4%) than in unsuccessfully ablated patients (mean 8.2%). Based on criterion 2, unsuccessful ablation was found in 52.4% of patients. The uptake-related ablation strategy, using low doses of 131I, shows a relatively high treatment failure rate. Based on these results it is suggested that a lower ablation failure rate could be achieved by applying higher 131I doses in the ablation of thyroid remnants in differentiated thyroid carcinoma patients. In the case of lymph node metastases a further dose adjustment may be advisable.