The incidence of (para) thyroid disorders ten years after the introduction of a new thyroid protection during 131I-MIBG treatment in children with neuroblastoma

During treatment with 131I-Meta-iodobenzylguanidine (MIBG) for childhood
neuroblastoma (NBL) the thyroid gland may be damaged by exposure to
radio-iodine. For this reason, in Emma Children*s Hospital, up to 1999, the
thyroid gland during treatment with 131I-MIBG was protected against uptake of
131I¯ by the administration of potassium-iodide (KI). Despite this protection,
a high incidence of thyroid dysfunction was found (in 56 % of survivors an
elevated thyrotropin (TSH) concentration) and in a high percentage of the
scintigraphic images (21%) uptake of radio-iodide in the thyroid was seen.For
this reason, from 1999, a new thyroid protection was introduced, consisting of
KI, methimazole and thyroxine (Dilute, Block and Replace = DBR). After a period
of two years, in 2001, the new thyroid protection resulted in a decreased
occurrence of TSH elevations (17 %) and a decreased number of visible thyroid
glands on the scintigram (5 %). It has now been more than 10 years ago that the
DBR protection was introduced, but it*s efficacy has never again been
evaluated. Unfortunately, recently, two NBL survivors have been diagnosed with
papillary thyroid carcinoma; both had received treatment with 131I-MIBG, one
was given KI protection and the other DBR. As the prevalence of thyroid
disorders after exposure to irradiation increases with time, we must
re-evaluate the incidence of thyroid problems in the children ten years after
introduction of the new DBR prophylaxis. Furthermore we will check for
hyperparathyroidism and or the occurrence of parathyroid adenomas in all
survivors, since this has been described after MIBG treatment. In addition we
will evaluate linear growth and pubertal development in the survivors, given
that small stature and late puberty have been described after NBL treatment.

Long-term evaluation of thyroid disorders ( TSH elevation and the occurrence of
thyroid nodi/carcinoma) in survivors of childhood NBL who received KI,
methimazole and thyroxine as thyroid protection during 131I-MIBG exposure.
Investigation of the incidence of hyperparathyroidism and or the occurrence of
parathyroid adenomas.

Prospective cohort study

There is no risk for the patients. During a routine vena puncture for other
reasons, also blood with be withdrawn for measuring of thyroid function.
Thyroid ultrasonography is not painfull and will last only 15 minutes. If a
thyroid nodule is found, the patient will be referred to the pediatric
endocrinologist for further diagnostics according to routine patient care.