Correlation Between Cervical Uptake and Results of Postsurgical Radioiodine Ablation in Patients With Thyroid Carcinoma

OBJECTIVE: The objective of this study was to determine the relationship between cervical uptake after thyroidectomy and the success of treatment of cervical remnants with high-dose radioiodine (100 mCi). METHODS: Cervical uptake was retrospectively analyzed after total thyroidectomy and before treatment with radioactive iodine in 142 patients seen at our service who received 100 mCi iodine-131 and whose posttreatment scan only showed cervical uptake without distant metastases. The patients were divided into 5 groups according to the uptake result obtained before ablative therapy. RESULTS: Successful treatment, defined as stimulated thyroglobulin levels <5 ng/mL and a clean scan or only discrete cervical uptake (0.5%) 6 months to 1 year after surgery, was obtained as follows: patients with uptake <1% (n = 48) showed 95.8% treatment efficacy, those with uptake of 1-2% (n = 32) 94% efficacy, and those with uptake of 2-5% (n = 30) reached 83% success, whereas patients with uptake of 5-10% (n = 20) presented 70% efficacy, and treatment was successful in only 50% of patients with uptake >10% (n = 12). CONCLUSIONS: Postoperative measurement of cervical I-131 uptake could be a reasonable predictor of the success of the remnant ablation, and perhaps a guide in deciding the ablative dose of I-131, based on the inverse correlation between the uptake and ablation efficacy.