Endocrine Abstracts

Background: Treatment modalities for childhood neuroblastoma include chemotherapy, surgery, and radiotherapy. Metaiodobenzylguanidine (mIBG) scans labelled with radioisotopes can be used for diagnosis and disease surveillance (123 I-mIBG) and treatment (131 I-mIBG) in these patients. Thyroid dysfunction following mIBG scan exposure is a documented complication and thyroid protection with potassium iodide is recommended.

Aim: The audit aimed to identify the prevalence of thyroid dysfunction in a cohort of children diagnosed with neuroblastoma who received mIBG either for diagnosis or treatment.

Patients and method: Retrospective analysis of patient notes of those treated for high-risk neuroblastoma (patients with stage 4 disease over 1 year of age or MYCN amplified neuroblastoma) at the Great North Children’s hospital in Newcastle from 2005 to 2022.

Results: 30 patients received treatment for high-risk neuroblastoma over a period of 17 years; all patients had at least one 123 I-mIBG scan (average 7.3scans/patient). 3 patients had radiotherapy with 131 I-mIBG. 13 patients (43%) had abnormal thyroid function tests at some point after commencement of treatment. 7 patients have been started on thyroxine for subclinical hypothyroidism; all are believed to be related to MIBG exposure. Mean time post treatment completion to commencement of Thyroxine was 4 years (range 0-7years). All the patients prescribed thyroxine had received at least 4 mIBG scans (range from 4-19 scans). The remaining 6 patients are being monitored ‘off therapy’: (2 patients are believed to be ‘sick euthyroid’, 3 have normalised spontaneously and 1 has mildly reduced T4 levels with normal TSH.

Conclusion: This audit demonstrated a 43% prevalence of thyroid dysfunction in patients treated for high-risk neuroblastoma who had mIBG scans performed. We recommend surveillance with annual TFTs following completion of treatment in those subject to mIBG exposure. This audit suggests that there may be a link between number of mIBG exposures and likelihood of subsequent thyroid dysfunction.