High incidence of thyroid dysfunction despite prophylaxis with potassium iodide during (131)I-meta-iodobenzylguanidine treatment in children with neuroblastoma.
BACKGROUND
Treatment modalities like targeted radiotherapy with (131)I-meta-iodobenzylguanidine ((131)I-MIBG) improve survival rates after neuroblastoma (NB). Radiation to the thyroid gland can lead to hypothyroidism and even malignancy. Because hypothyroidism after (131)I-MIBG treatment was reported, the current KI prophylaxis against thyroidal radiation damage was evaluated.


METHODS
The incidence, pathogenesis, and consequences of thyroid dysfunction among 42 NB patients treated with (131)I-MIBG were evaluated retrospectively. Efficacy of KI prophylaxis was established by measuring thyroidal radioiodide uptake. Thyroid damage was expressed as thyrotropin elevation (TE, plasma concentration of thyroid stimulating hormone > or = 4.5 mU/L).


RESULTS
The mean followup was 2.3 years (range, 0.1-8.5). The mean number of treatments with (131)I-MIBG was 3.3. Of 428 scintigrams, uptake of (131)I in the thyroid was visible in 92 (21.0%). Twenty two patients (52.4 %) presented TE after a mean period of 1.4 years (range, 0.1-5.8). Clinical signs of hypothyroidism were not observed. Eight patients received suppletion therapy with thyroxine. Thyrotropin elevation was transient in four patients. Of 25 survivors, with a mean followup of 3.5 years, 16 (64%) developed TE. No correlation was found between TE and thyroid visualization after (131)I-MIBG administration or the number of treatments. No abnormalities were seen by ultrasound imaging of the thyroid.


CONCLUSIONS
Occurrence of thyroid dysfunction after treatment with (131)I-MIBG for NB is high, in spite of KI prophylaxis. Close followup of thyroid function and structure is required in patients treated with (131)I-MIBG. New ways of protecting the thyroid during exposure to radioiodine should be developed.
van Santen
Hanneke M
HM
Department of Pediatric Endocrinology, Emma Children's Hospital, Academic Medical Center G8-205, University of Amsterdam, 1100 DE Amsterdam, The Netherlands. vansanten@amc.uva.nl
de Kraker
Jan
J
van Eck
Berthe L F
BL
de Vijlder
Jan J M
JJ
Vulsma
Thomas
T
D019797:3-Iodobenzylguanidine / Q000009:adverse effects*; D000293:Adolescent; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009367:Neoplasm Staging; D009447:Neuroblastoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011193:Potassium Iodide / Q000627:therapeutic use*; D011292:Premedication; D011832:Radiation Injuries / Q000000981:diagnostic imaging / Q000209:etiology* / Q000517:prevention & control; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000009:adverse effects*; D012189:Retrospective Studies; D013959:Thyroid Diseases / Q000000981:diagnostic imaging / Q000209:etiology* / Q000517:prevention & control; D013961:Thyroid Gland / Q000187:drug effects / Q000528:radiation effects*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000627:therapeutic use
D019275:Radiopharmaceuticals; D011193:Potassium Iodide; D019797:3-Iodobenzylguanidine; D013972:Thyrotropin; D013974:Thyroxine