Objective: 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.
Methods: 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.
Results: 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.
Conclusion: 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.
Abbreviations: ATA = American Thyroid Association CI = confidence interval DTC = differentiated thyroid cancer OR = odds ratio ROC = receiver operating characteristic Tg = thyroglobulin.