Thyroid function after diagnostic I-metaiodobenzylguanidine in children with neuroblastic tumors.

BACKGROUND

Metaiodobenzylguanidine (MIBG) labeled with radioisotopes can be used for diagnostics I) and treatment (I) in patients with neuroblastic tumors. Thyroid dysfunction has been reported in 52% of neuroblastoma (NBL) survivors after I-MIBG, despite thyroid protection. Diagnostic I-MIBG is not considered to be hazardous for thyroid function; however, this has never been investigated. Therefore, the aim of this study was to evaluate the prevalence of thyroid dysfunction in survivors of a neuroblastic tumor who received diagnostic I-MIBG only.

METHODS

Thyroid function and uptake of I in the thyroid gland after I-MIBG administrations were evaluated in 48 neuroblastic tumor survivors who had not been treated with I-MIBG. All patients had received thyroid prophylaxis consisting of potassium iodide or a combination of potassium iodide, thiamazole and thyroxine during exposure to I-MIBG.

RESULTS

After a median follow-up of 6.6 years, thyroid function was normal in 46 of 48 survivors (95.8%). Two survivors [prevalence 4.2% (95% CI 1.2-14.0)] had mild thyroid dysfunction. In 29.2% of the patients and 11.1% of images I uptake was visible in the thyroid. In 1 patient with thyroid dysfunction, weak uptake of I was seen on 1 of 10 images.

CONCLUSIONS

The prevalence of thyroid dysfunction does not seem to be increased in patients with neuroblastic tumors who received I-MIBG combined with thyroid protection. Randomized controlled trials are required to investigate whether administration of I-MIBG without thyroid protection is harmful to the thyroid gland.