Lithium as an adjuvant in the postoperative ablation of remnant tissue in low-risk thyroid carcinoma.

Background: Thyroid remnant ablation (RA) with 30 mCi of radioactive iodine (I-131) in patients thyroidectomized for treatment of low-risk differentiated thyroid carcinoma (DTC) has a success rate of 64% to 84%. Lithium increases the residence time of I-131 in the thyroid tissue. The aim of this study was to determine if lithium treatment added to 30 mCi I-131 would enhance the success rate of this treatment compared with 30 mCi I-131 alone in patients who were thyroidectomized for treatment of low-risk DTC. Methods: This was a randomized study with endpoint at one year. Sixty one consecutive patients were enrolled and randomized into two groups: group A (n = 32) treated with 30 mCi I-131; group B (n = 29) treated with 30 mCi I-131 plus an oral dose of lithium 900 mg/day, for 7 days. All patients were evaluated by whole body scan (WBS) with I-123 and had serum TSH, thyroglobulin (Tg), and anti-Tg antibodies (TgAb) determined when they were hypothyroid on no thyroid hormone. Patients were reevaluated after one year with serum TSH, Tg, and TgAb determinations and WBS with I-123. The criteria for defining a successful outcome was a negative WBS and a serum Tg of < 1. Results: Group A was composed of 28 women and four men (ages 25-71 years) with 2 having follicular thyroid carcinoma (FTC), 22 having papillary thyroid carcinoma (PTC) of 1-4.5 cm, and 8 having micro PTCs (mPTC) of 0.3-0.8 cm. Group B was composed of 26 women and 3 men (ages 20-63 years) with 3 having FTC, 15 having PTC of 1.2-3.5 cm, and 11 having mPTC of 0.2-0.8 cm. All patients had a history of a WBS after their post-therapeutic I-131 dose that showed uptake in the cervical region. After one year, 22 patients from group A had a negative WBS (68.75%) and in group B, 27 patients had a negative WBS (93.1%). The successful rates for the follow-up WBS were significantly different (p = 0.017). There were 19 patients in Group A in whom the initial Tg was positive. Of these, 14 had a negative follow-up Tg (73.7%). Group B had 9 patients with a positive initial Tg and all of them had a negative follow-up Tg (100%). Conclusion: The addition of lithium to treatment with 30 mCi I-131 in thyroidectomized patients with low-risk DTC improved the efficacy of thyroid RA and therefore might be a better alternative than using higher doses of I-131 for remnant ablation in these patients.