Reduced Thyroid Volumes after 131I-Metaiodobenzylguanidine Treatment in Children with Neuroblastoma: Need for Further Improvement of Thyroid Protection

S.C. Clement MD1,2, R.R. van Rijn MD PhD3, B.L.F van Eck-Smit MD PhD4, A.S.P. van Trotsenburg MD PhD1, H.N. Caron MD PhD2, G.A.M. Tytgat, MD PhD2, H.M. van Santen MD PhD5

1 Department of Pediatric Endocrinology, Emma Children’s Hospital, Academic Medical Center, University of Amsterdam, PO box 22660, 1100 DD, Amsterdam, The Netherlands.

2 Department of Pediatric Oncology, Emma Children’s Hospital, Academic Medical Center, University of Amsterdam, PO box 22660, 1100 DD, Amsterdam, The Netherlands.

3 Department of Radiology, Emma Children’s Hospital, Academic Medical Center, University of Amsterdam, PO box 22660, 1100 DD, Amsterdam, The Netherlands.

4 Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, PO box 22660, 1100 DD, Amsterdam, The Netherlands.

5 Department of Pediatric Endocrinology, Wilhelmina Children’s Hospital/ University Medical Center Utrecht, PO Box 85090, 3508 AB, Utrecht, The Netherlands.

Corresponding author: Drs. S.C. Clement, Department of Pediatric Endocrinology, TKs0-227 Emma Children's Hospital/Academic Medical Center, PO Box 22660, 1100 DD Amsterdam, the Netherlands. Phone: +31-20-5668974, Fax: +31-20-5669021, Email:

Journal: European Journal of Nuclear Medicine and Molecular Imaging

Appendix 1. Thyroid protection at the time of MIBG administration for the diagnosis and treatment of neural crest tumour’s

A) Thyroid protection for diagnostic procedures with 123I-MIBG:

Drug / Dose / Start
Thyroxine / 125 mcg/m2 in one dose during 3 days / 1 day before administration of MIBG
Methimazole / 0.5 mg/kg/day in two gifts during 3 days / 1 day before administration of MIBG
Potassium-iodide / 3 dd 0.3 ml 10 % solution (= 100 mg/ml) during 2 days / The morning of administrating MIBG

B) Thyroid protection during therapeutic 131I-MIBG:

Drug / Dose / Start /

Remarks

Thyroxine / 125 mcg/m2 in one dose during 4 weeks / 1 day before administration of MIBG / If followed by a 2nd or 3rd MIBG treatment, continue the drug
Methimazole / 0.5 mg/kg/dag in one dose during 4 weeks / 1 day before administration of MIBG / If followed by a 2nd or 3rd MIBG treatment, continue the drug
Potassium-iodide / 3 dd 0.3 ml 10 % solution (= 100 mg/ml) during 2 weeks / The morning of administrating MIBG / If followed by a 2nd or 3rd MIBG treatment, restart the drug on the morning of next MIBG administration

C) Thyroid protection for the parents (during therapeutic 131I-MIBG)

Drug / Dose / Start
Potassium-iodide / 200 mg in 1 dose during 4 days / The day before administration of 131I-MIBG to the child

Attention: do not administer potassium-iodide to pregnant women !!

Monitoring of thyroid function:

Before start protection:-FT4, TSH

During protection: After 1 week, and right before the 2nd131I-MIBG

(see flowchart)-FT4, TSH

(Goal-values: TSH 0.2-1.0 mU/L, FT4 12-30 pmol/L)

-Hb, Ht, Leuco + diff, SGOT, SGPT (for rare complications methimazole)

After stopping protection:After 1 month, subsequently every three months during 2 years. After a period of 2 years, once every 6 months.

- FT4, TSH

Guideline for adjusting thyroxine dose during protection

Check TSH and FT41 week after starting protection

 right before 2nd131I-MIBG treatment


The biochemical aim of the thyroid protection is to reach a plasma concentration of TSH < 1.0 mU/L with FT4 <30 pmol/L during exposure to radio-MIBG. During the thyroid protection the right setpoint is reached by adjusting the thyroxine dose (the dose of methimazole and potassium-iodide are not changed) .

A consultation of the department pediatric endocrinology is advised in presence of:

-TSH 4.5 mU/L

-FT4 lower than 12 pmol/L or higher than 35 pmol/L

-Clinical signs or symptoms of hyper- or hypothyroidism

-Other questions regarding the thyroid function or this thyroid protection