Trial Information

The Effects of Lithium Carbonate on Low Dose Radioiodine Ablation in Early Thyroid Cancer Treatment

Postsurgical thyroid remnant ablation with (131)I is considered standard clinical care for
most cases of papillary and follicular thyroid cancer, to eliminate normal thyroid tissue
which may contain microscopic cancer. Furthermore, ablation enhances the sensitivity of
subsequent (131)I scanning and serum thyroglobulin (TG) measurement for the detection of
recurrent or persistent disease. Low dose (131)I (30 mCi) successfully ablates thyroid
remnant in 8-61% of cases. This dose can be repeated and result in overall less radiation
exposure than that associated with high dose therapy (100 mCi). Ablation achieved with one
or more small doses of radioactive iodine is not associated with decreased survival or
cancer recurrence. According to the literature there is no difference in the 30-year
recurrence rates between groups receiving low and high dose ablation therapy for well
differentiated thyroid cancer without distant metastases at the time of initial therapy. The
benefits of using low dose of (131)I are minimization of whole body radiation exposure,
reduction in side effects and lower cost. Higher rates of successful ablation by low dose of
131I could be achieved by increasing uptake of (131)I and/or lengthening retention of
radioiodine in the remnant thyroid tissue. Recombinant human thyroid-stimulating hormone
(rhTSH) has been used successfully to increase radioiodine uptake. Lithium has been used to
increase radioiodine retention and has been shown to be useful in the treatment of residual
or metastatic cancer. The combination of rhTSH and lithium as adjuncts to 30 mCi radioactive
iodine (RAI) ablation therapy in low risk thyroid cancer patients may provide a method that
reduces the cumulative dose of radioiodine needed to successfully treat thyroid cancer. The
specific aim of this study is to determine whether adjunct lithium carbonate improves the
success rate of postsurgical ablation of thyroid remnants using low dose (131)I (30 mCi) and
rhTSH in low risk patients with differentiated thyroid carcinoma. Patients with
well-differentiated papillary or follicular thyroid cancer stage I or II, according to the
National Thyroid Cancer Treatment Cooperative Study (NTCTCS) classification at time of
surgery, will be enrolled. Eligible patients will have had a total or near-total
thyroidectomy within 6 months of enrollment. This randomized, placebocontrolled,
double-blind study will permit an evaluation of the risk/benefit ratio of adding lithium as
an adjuvant to the already established method of administering low-dose (131)I ablation
therapy, to optimize the (131)I retention. All patients will undergo diagnostic rhTSH (123)I
whole body scan at the end of the study to assess the success of thyroid ablation.