The relationship between thyroid dose and diagnosis of primary hypothyroidism in pediatric brain tumor patients receiving craniospinal irradiation

Abstract

Purpose The aim of this work is to determine if a relationship exists between thyroid dose and incidence of primary hypothyroidism (PH) in children undergoing craniospinal irradiation (CSI). Methods A total of 22 patients received CSI with evaluable thyroid dose information. All patients received concurrent chemotherapy and 21 patients (95%) received adjuvant chemotherapy. Median follow-up was 42.9 months. Results The incidence of PH in our cohort was 59% at a median time after radiotherapy of 3.5 years (range: 8 months to 7.5 years). Mean thyroid dose appeared to best predict for PH, with a median of 2080 cGy for patients with PH versus 1736 cGy for children without PH (p=0.057). There was no association between the rate of PH and sex, age, CSI dose, minimum thyroid dose and maximum thyroid dose. Conclusions A relationship may exist between the mean thyroid dose and incidence of PH in patients undergoing CSI. Thus, new strategies to protect the thyroid gland may be warranted.

Thyroid Sequelae of Pediatric Cancer Therapy

“…The risk for and degree of thyroid dysfunction depends on several factors, primarily the dose of radiation to the thyroid (the higher the dose, the higher the risk; risk greatest with thyroid doses ≥25 Gy) as well as the age of the patient at the time of treatment (the younger the age, the higher the risk; risk greatest <age 5 years) [8, 18, 19, 21, 22, 37, 39, 46, 50, 51]. As would be expected, a reduction of thyroid gland volume occurs after irradiation and is correlated with the risk for the development of hypothyroidism [52, 53].…”