Appropriateness of 14-year cutoff in pediatric differentiated thyroid cancer: Comparison of clinical characteristics and long-term outcomes in 14 years and younger and 15-18 years age groups.

BACKGROUND: Pediatric differentiated thyroid cancers (DTCs) differ in pathophysiology, presentation, and clinical outcomes from adult DTCs. However, the cutoff age for defining pediatric DTCs remains debatable, with the American Thyroid Association (ATA) and International Incidence of Childhood Cancer (IICC) report recommending different cutoffs of 18 and 14 years, respectively. In this study, we investigated the appropriateness of 14-year cutoff by comparing the clinical characteristics and long-term outcomes in the 14 years and younger and 15-18 years age groups. METHODS: Data of DTC patients, aged 18 years and older, from 1981 to 2016, were sequentially extracted and compared between two age groups: ≤14 and 15-18 years. RESULTS: Total of 176 pediatric DTC patients were included (age group ≤14 years: n = 75; age group 15-18 years: n = 101). None of the baseline clinical characteristics were significantly different between the two age groups. At 2-year follow-up, patients in the age group ≤14 years had significantly higher incomplete response rate compared to those in the age group 15-18 years (69% vs. 42%, respectively, p < .001). However, over a median follow-up of 10.6 years (interquartile range: 7.7-15.5), the 5- and 10-year Disease-free survival (DFS) probabilities were not significantly different (p = .406). On multivariate analysis, incomplete response at 2-year follow-up was the sole independent predictor of poor DFS (hazard ratio: 5.85, 95% confidence interval: 1.69-20.23). CONCLUSIONS: Subdivision of pediatric DTCs into less than or equal to 14 years and 15-18 years age groups did not have any long-term predictive value. The cutoff of 18 years as recommended by ATA is reasonable and should be uniformly followed to avoid inconsistencies and confusion.

Differentiated Thyroid Cancers in Young Adults Versus Children: Clinical Characteristics and 10-year Follow-up Outcomes.

BACKGROUND: Differentiated thyroid cancer (DTC) in young adults has been steadily rising in incidence over the decades. However, data on long-term outcomes in this specific cohort remain limited. In this study, we intended to evaluate young adults with DTC with regard to their clinical characteristics and treatment outcomes and compare the same vis-à-vis pediatric patients with DTC. METHODS: Data of pediatric (≤18 years) and young adult (19-39 years) patients with DTC, from 1971 to 2016, were sequentially extracted and analyzed for clinical characteristics, treatment responses, rates of recurrent/persistent disease, and disease-free survival (DFS). RESULTS: A total of 1803 patients with DTC were included (pediatric cohort: n = 176; young adult cohort: n = 1627). Pediatric patients with DTC had more frequent adverse baseline features including extrathyroidal extension (P = .040), nodal and distant metastases, and American Thyroid Association high-risk disease (P < .001 each). At 2 years posttreatment, young adult patients with DTC had significantly lower incomplete responses compared with pediatric patients with DTC (223/1627; 13.7% vs 94/176, 53.4%, respectively; P < .001). Over a median follow-up of 10.7 years, 120/1627 (7.4%) young adult patients with DTC had recurrent/persistent disease vs 23/176 (13.1%) pediatric patients with DTC (P = .012). The 10-year DFS probability was 93.6% for the young adult patients with DTC vs 88.7% for the pediatric patients with DTC (P = .007). American Thyroid Association high-risk disease and incomplete response at 2 years were independent predictors of significantly worse DFS in the young adult cohort (P < .001 each). CONCLUSIONS: Young adult DTCs behave less aggressively compared with their pediatric counterparts with excellent long-term outcomes. Appropriate initial and dynamic risk stratification can help optimize treatment decisions and follow-up strategies.

Dynamic Risk Stratification for Predicting Long-term Outcomes in Pediatric Differentiated Thyroid Cancers.

CONTEXT: The American Thyroid Association (ATA) guidelines recommend Dynamic Risk Stratification (DRS) for predicting long-term outcomes and personalizing management in adult differentiated thyroid cancers (DTCs). However, its applicability in pediatric DTCs needs to be validated. OBJECTIVE: We have attempted a validation study concerning the use of DRS in pediatric DTCs. METHODS: Data of children (age ≤18 years) with DTCs and follow-up of ≥5 years were extracted. All patients were classified according to DRS (excellent biochemical or structural incomplete responses). Univariate and multivariate analyses were done to identify factor(s) affecting disease-free survival (DFS). RESULTS: We included 176 pediatric patients with DTC (median age at diagnosis 15 years). All patients underwent thyroidectomy and received radioiodine as part of initial management. On the basis of clinical, biochemical, and imaging findings acquired during the first 2 years of follow-up, the DRS system divided patients into 3 response categories: excellent response in 82/176 (46.6%), biochemical incomplete response in 56/176 (31.8%), and structural incomplete response in 38/176 (21.6%) patients. The median follow-up was 10.6 years (interquartile range 7.7-15.5). Ten-year overall survival and DFS rates were 100% and 88.7%, respectively. In univariate analysis, DFS was significantly affected by extrathyroidal extension (P = .002), lymph node metastasis (P = .018), ATA initial risk stratification (P = .033), and DRS (P = .004). However, in multivariate analysis, DRS alone showed a significant association with DFS (P = .016). CONCLUSION: Like adults, DRS correctly predicts long-term outcomes in pediatric DTC. In addition to ATA initial risk stratification, DRS could further refine risk in pediatric DTCs and help in planning more personalized treatment and follow-up strategies.