Pre-Ablation Thyroglobulin and Thyroglobulin to Thyroid-Stimulating Hormone Ratio may be Associated with Pulmonary Metastases in Children with Differentiated Thyroid Cancer

Abstract

Pediatric differentiated thyroid cancer (DTC) frequently presents with extensive disease. We studied the value of pre-ablation thyroglobulin (Tg) and Tg normalized to thyroid-stimulating hormone (TSH) levels in predicting distant metastases in pediatric patients with DTC. This is a retrospective cohort study of patients <21 years old who underwent thyroidectomy followed by 131I ablation for DTC at 3 university hospitals over 20 years. Tg levels and the Tg/TSH ratio following surgery but prior to 131I ablation were assessed. The presence of distant metastatic disease was determined from the postablation whole-body scan. We studied 44 patients with a mean age of 15.2 years (range 7 to 21 years) and mean tumor size of 2.8 cm. Eight patients had distant metastases and had a higher mean pre-ablation Tg value compared to patients without distant metastases (1,037 μg/L versus 93.5 μg/L, P<.01). The pre-ablation Tg/TSH ratio was also associated with the presence of distant metastases: 12.5 ± 18.8 μg/mU in patients with distant metastases versus 0.7 ± 1.8 μg/mU in patients without (P<.01). A nomogram to predict distant metastases yielded areas under the receiver operating characteristic curve of 0.85 for Tg and 0.83 for Tg/TSH ratio. After initial thyroidectomy, elevated preablation Tg and Tg/TSH ratio are associated with distant metastatic disease in pediatric DTC. This may inform the decision to ablate with 131I, as well as the dosage. ATA = American Thyroid Association CI = confidence interval DTC = differentiated thyroid cancer OR = odds ratio ROC = receiver operating characteristic Tg = thyroglobulin.