Outpatient Thyroid Remnant Ablation Using Repeated Low 131-Iodine Activities (740 MBq/20 mCi × 2) in Patients with Low-Risk Differentiated Thyroid Cancer

Context: In low-risk differentiated thyroid cancer (DTC), postoperative 131I remnant ablation should employ a minimum effective activity; reports increasingly suggest efficacy of low activities, e.g. 1110 MBq/30 mCi. Objectives, Design, Patients, and Interventions: We retrospectively studied the ablation capability and diagnostic utility of the Minidose protocol, two 740-MBq/20 mCi outpatient administrations, 6–18 months apart, plus related diagnostic procedures, in 160 consecutive (near-) totally thyroidectomized low-risk DTC (pT1/N0-Nx) patients. Successful ablation comprised negative 740-MBq whole-body scintigraphy with cervical uptake below 0.1%, negative stimulated thyroglobulin (STg) (<1 ng/ml, negative thyroglobulin antibodies), and negative Doppler ultrasonography (performed around Minidose 2). Setting: The study took place at a referral center. Results: Minidose imaging found unsuspected nodal or distant metastases in nine of 160 patients (5.6%). Ablation success rates after one (two) 740-MBq act...