PRE-ABLATION THYROGLOBULIN AND THYROGLOBULIN TO THYROID-STIMULATING HORMONE RATIO MAY BE ASSOCIATED WITH PULMONARY METASTASES IN CHILDREN WITH DIFFERENTIATED THYROID CANCER

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 134 ablation for DTC at 3 university hospitals over 20 years. Tg levels and the Tg TSH ratio following surgery but prior to I-131. ablation were assessed. The presence of distant metastatic disease was determined from the postablation whole-body scan. Results: We studied-14 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 mu g/L, versus 93.5 mu g/L, P<.01.). The pre-ablation Tg TSH ratio was also associated with the presence of distant metastases: 12.5 +/- 18.8 mu g/mU in patients with distant metastases versus 0.7 +/- 1.8 mu g/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 pre ablation Tg and Tg TSH ratio arc associated with distant metastatic disease in pediatric DTC. This may inform the decision to ablate with I-131, as well as the dosage.