Late Effects of the Endocrine System
As might be expected, children treated for head and neck malignancies are also at risk for primary hypothyroidism if the neck is irradiated. The German Group of Paediatric Radiation Oncology recently reported on 1,086 patients treated at 62 centers, including 404 patients (median age, 10.9 years) who had received radiation therapy to the thyroid gland and/or hypophysis. Follow-up information was available for 264 patients (60.9%; median follow-up, 40 months), with 60 patients (22.7%) showing pathologic values. In comparison to patients treated with prophylactic cranial irradiation (median dose, 12 Gy), patients with radiation doses of 15 Gy to 25 Gy to the thyroid gland had a hazard ratio (HR) of 3.072 (P = .002) for the development of pathologic thyroid blood values. Patients with greater than 25 Gy to the thyroid gland and patients who underwent craniospinal irradiation had HR of 3.768 (P = .009) and 5.674 (P < .001), respectively. The cumulative incidence of thyroid hormone substitution therapy did not differ between defined subgroups.
Survivors of pediatric hematopoietic stem cell transplant are at increased risk of thyroid dysfunction, with the risk being much lower (15%-16%) after fractionated total-body irradiation (TBI), as opposed to single-dose TBI (46%-48%). Non-TBI-containing regimens historically were not associated with an increased risk. However, in a report from the Fred Hutchinson Cancer Research Center, the increased risk of thyroid dysfunction was not different between children receiving a TBI or busulfan-based regimen (P = .48). Other high-dose therapies have not been studied. While mildly elevated TSH is common, it is usually accompanied by normal thyroxine concentration.[11,12]
Table 6. Thyroid Late Effects
TSH = thyroid stimulating hormone.
|Predisposing Therapy ||Endocrine/Metabolic Effects||Health Screening|
|Radiation impacting thyroid gland; thyroidectomy ||Primary hypothyroidism||TSH level|
|Radiation impacting thyroid gland ||Hyperthyroidism||Free thyroxine (Free T4) level|
|Radiation impacting thyroid gland ||Thyroid nodules||Thyroid exam |
Refer to the Children's Oncology Group Long-Term Follow-Up Guidelines for Survivors of Childhood, Adolescent, and Young Adult Cancers for endocrine late effects information including risk factors, evaluation, and health counseling.
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