Distant Metastases and Outcome of Pediatric Differentiated Thyroid Cancer

Context Distant metastases are fairly common in pediatric differentiated thyroid cancer (DTC). Objective Our objectives were to study the predictive factors of distant metastases and the outcome of pediatric DTC. Methods We studied all patients with pediatric DTC (age <= 18 years) managed over 21 years (January 2002-December 2022) at our institution. A total of 192 patients (33 males [17.2%], 159 females [82.8%]) with pediatric DTC were analyzed. The median age was 16 years (range, 5-18 years). Total thyroidectomy was performed in 97%, lymph node dissection in 86.4%, and radioactive iodine-131 (I-131) ablation/therapy was administered to 85.4% of the patients. Additional therapies were administered to 65 patients (33.9%). Thirty-five patients (18.2%) developed distant metastases. Results At the last follow-up (median follow-up, 82.5 months; interquartile range 48-132), 124 patients (64.6%) had an excellent response, 47 (24.5%) had an indeterminate response, 5 (2.6%) were in a biochemically incomplete response, 15 (7.8%) were in a structurally incomplete response, and 1 patient (0.5%) died of thyroid cancer. While tumor size, extrathyroidal extension/invasion, and distant metastases were predictive of persistent/recurrent disease in a univariate analysis, only distant metastases remained consistently predictive of persistent/recurrent disease in a multivariate analysis (P < .0001; odds ratio 8.9; 95% CI, 3.2-25.0). In a multivariate analysis, predictors of distant metastases were tumor size (P = .004; odds ratio 1.41; 95% CI, 1.11-1.76) and extrathyroidal extension (P = .001; odds ratio 13.7; 95% CI, 3.1-60.6). Conclusion In pediatric DTC, distant metastases are common, especially in patients with large tumor size and extrathyroidal extension. Distant metastases are the most important predictive factor of persistent/recurrent disease.