Hypothyroidism after 131I-monoclonal antibody treatment of neuroblastoma

To determine the prevalence of and risk factors for primary hypothyroidism following treatment with a radiolabeled monoclonal antibody ((131)I-3F8) in children with neuroblastoma.

In the current study, we assessed thyroid function in 51 neuroblastoma patients who survived for > or =3 months after treatment with (131)I-3F8 (a murine IgG3 monoclonal antibody that reacts with the ganglioside GD2) at 4 mCi/kg/day x 5 days (total 20 mCi/kg). Prior therapy in all subjects included dose-intensive chemotherapy; 13 subjects also received external beam radiation to the neck. Oral iodide and liothyronine sodium (T3) were administered for protection of the thyroid gland.

Thirty-two of 51 subjects (63%) developed hormonal evidence of primary hypothyroidism. The median time to hypothyroidism after treatment with (131)I-3F8 was 6.4 months. The probability of developing hypothyroidism was 56% at 2 years following treatment with (131)I-3F8. There was evidence for an association between thyroidal uptake of (131)I and development of hypothyroidism (hazard ratio 1.83, 95% confidence interval 0.91-3.30; P = 0.09).

We conclude that hormonal evidence of primary hypothyroidism developed in a majority of subjects treated with (131)I-3F8, despite pretreatment with oral iodide plus liothyronine sodium. Alternative strategies for thyroid gland protection are needed.