Objectives: To describe a cohort of survivors of childhood malignancy at risk of developing thyroid abnormality, and propose guidelines for management of such patients.
Design: Retrospective case series.
Setting: Late-effects oncology clinic at a large children's hospital in Sydney.
Subjects: 142 patients who had received irradiation to the thyroid from the 1970s onwards, who attended the late-effects clinic from May 1989 to December 1998.
Interventions: Thyroid palpation by an endocrinologist or surgeon, serum thyroid-stimulating hormone assay and thyroid ultrasound examination were performed on all subjects and, depending on findings, some subjects proceeded to fine-needle biopsy or surgery (total thyroidectomy). A few patients required adjuvant (131)I administration.
Outcome measures: Radiation dose received; results of thyroid palpation; thyroid function tests; ultrasound findings; diagnosis of the abnormalities; and outcomes of surgical interventions.
Results: 49 subjects (24 of 65 patients who received scatter irradiation to the thyroid and 25 of 78 patients who received direct irradiation) had thyroid surgery. Of these, 12 in the scatter and six in the direct irradiation group were found to have thyroid malignancy. Fifty subjects with abnormal ultrasound results remain under surveillance. Having a palpable thyroid was predictive of malignancy, but age at original diagnosis, sex, current age, time since irradiation, radiation dose, nodule type and nodal involvement were not.
Conclusion: There is a significant risk of cancer in thyroid glands exposed to radiation as part of therapy for childhood cancer. This risk is greater for patients who received scatter (versus direct) irradiation. Nodular change is usually not apparent for many years, so lifelong surveillance is necessary. Palpation alone is not sufficient to detect thyroid cancer and thyroid ultrasound examination is recommended.