Salivary and lacrimal gland dysfunction after remnant ablation with radioactive iodine in patients with differentiated thyroid carcinoma prepared with recombinant human thyrotropin.

BACKGROUND: One of the adverse effects of radioactive iodine (¹³¹I) treatment in patients with thyroid cancer is damage to the salivary and lacrimal glands. In almost all studies evaluating salivary and lacrimal gland dysfunction, the patients received ¹³¹I after levothyroxine (L-T4) withdrawal. Since the biokinetics of ¹³¹I after recombinant human thyrotropin (rhTSH) is not the same as in hypothyroidism, studies need to evaluate ¹³¹I-induced salivary and lacrimal toxicity after preparation with rhTSH. This prospective study investigated the occurrence of salivary and lacrimal damage after ablation with ¹³¹I using this preparation.

METHODS: One hundred forty-eight patients who had a total thyroidectomy were included in the study. The subjects were evaluated after thyroidectomy during L-T4 use to exclude those who already showed symptoms or had a history of ocular or oral disease. Symptoms were investigated 12 and 18 months after ablation. In patients who had persistent symptoms, specific tests were performed to confirm glandular dysfunction and to rule out other causes.

RESULTS: Twelve months after ablation, symptoms of salivary or lacrimal dysfunction were observed in 10 (6.7%) patients, including oral symptoms in 8 (5.4%) and ocular symptoms in 6 (4%). Eighteen months after ¹³¹I, symptoms persisted in eight (5.4%) patients, including oral symptoms in seven (4.7%) and ocular symptoms in five (3.4%). In all of the patients, glandular dysfunction was confirmed by specific tests and other causes were ruled out. No symptoms were seen in the patients who received a low ¹³¹I dose (30 mCi). In the patients who received high ¹³¹I doses (100 or 150 mCi), symptoms were noted 12 months after ¹³¹I in 10 patients (9.2%), and 18 months after ¹³¹I in 8 patients (7.4%).

CONCLUSIONS: Apparently, the rates of salivary and lacrimal damage were lower than those reported in prospective studies that used similar ¹³¹I activities, but these studies were performed in patients who were hypothyroid at the time of ¹³¹I ablation. Further studies are needed to compare radiotoxicity between patients prepared for ¹³¹I ablation with rhTSH and those prepared for ¹³¹I ablation with L-T4 withdrawal.