MON-210 The Clinical and Pathological Profile and Predictors of Outcome of Pediatric Thyroid Cancer

Abstract Disclosure: G.S. Alskait: None. Y. Aljufan: None. S. Alghaihb: None. A. Alkhalifah: None. L. AlAyoubi: None. A. Abualnaja: None. L. Alobaid: None. E. Albasri: None. A.S. Alzahrani: None. Introduction: Although increasing in incidence, pediatric differentiated thyroid cancer (DTC) remains rare. Our objectives in this study were to study the clinical and histopathological profile, staging, rate of metastases and factors associated with distant metastases and outcome in pediatric DTC. Patients and methods: We studied all patients with pediatric DTC (age ≤ 18 years) managed over 20 years (January 2002-December 2022) at our institution and analyzed the data for clinical and histopathological profiles, rates, and predictors of distant metastases and rates and predictors of the final outcome. Results: 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). The tumor types were classic PTC in 134 patients (69.8%), follicular variant PTC in 24 cases (12.5%), tall cell variant PTC in 9 patients (4.7%), diffuse sclerosing type PTC in 11 patients (5.7%), follicular thyroid cancer in 7 patients (3.6%), oncocytic cell thyroid cancer in 3 cases (1.6%), poorly differentiated thyroid cancer in 2 patients (1%), columnar cell variant in 1 patient (0.5%) and Hyalinizing trabecular variant in 1 patient (0.5%). Lymph node metastases were found in 65.5 % (126 pts) and distant metastases in 18.2% (35 pts). At the initial management, the TNM staging was stage 1 in 84.4% and stage II in 15.6%. The ATA risk groups included 22% in high risk, 44.2% intermediate risk and 28.1% in low risk while data was not available to risk stratify 11 pts (5.7%). Total thyroidectomy was performed in 97%, lymph node dissection in 86.4% and I-131 ablation/therapy administered to 85.4% of the patients. Due to persistent or progressive disease, additional therapies including one or more of additional surgeries, I-131, external beam radiotherapy, and/or tyrosine kinase inhibitors were administered to 65 patients (33.9%). At the last follow-up (median follow-up 82.5 months, IQR 48-132), 124 patients (64.6%) were in an excellent response, 47 (24.5%) in an indeterminate response, 5 (2.6%) biochemically incomplete, 15 (7.8%) structurally incomplete, and 1 patient (0.5%) died due to thyroid cancer. While tumor size, extrathyroidal extension/invasion and distant metastases predicted persistent disease in univariate analysis, only distant metastases remained consistently predictive of persistent disease in multivariate analysis (P <0.0001, odd ratio 8.9, 95% CI 3.2-25.0). In a multivariate analysis, predictors of distant metastases were tumor size (P 0.004, odds ratio 1.41 (95% CI 1.11-1.76) and extrathyroidal extension (P 0.001, odd ratio 13.7 (95% CI 3.1-60.6). Conclusion: Pediatric thyroid cancer is characterized by high rates of lymph node and distant metastases but low mortality. Distant metastases are associated with large tumor sizes and extrathyroidal extension and are the most important predictive factor of persistent disease. Presentation: Monday, July 14, 2025