Comparison of Outcomes After 123I Versus 131I Preablation Imaging Before Radioiodine Ablation in Differentiated Thyroid Carcinoma

Detection of residual tissue after thyroidectomy for papillary or follicular thyroid carcinoma may be performed using diagnostic imaging with either 123I or 131I. The former is often preferred to avoid ‘‘stunning’’—defined as a reduction in uptake of the thera-peutic dose of 131I caused by some form of cell damage from the diagnostic dosage of the radionuclide. Stunning could potentially reduce the therapeutic efficacy of 131I given to ablate a postthy-roidectomy remnant. This study examines the outcomes of abla-tive 131I therapy after diagnostic studies with either 123I or 131I to determine if the diagnostic dosages of these radionuclides used in our Thyroid Cancer Center reduce the efficacy of 131I given for remnant ablation. Methods: Fifty patients with nonmetastatic papillary or follicular carcinoma of the thyroid received total thyroidectomy; this was followed by thyroid hormone withdrawal to achieve a serum thyroid-stimulating hormone level in exces