Differentiated thyroid cancers in young adults versus children: Clinical characteristics and ten-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 remains limited. In this study, we intended to evaluate young adult DTCs with regard to their clinical characteristics and treatment outcomes, and compare the same vis-à-vis pediatric DTCs.

METHODS: Data of pediatric (≤18 years) and young adult (19-39 years) DTC patients, 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: 1803 DTC patients were included (pediatric cohort: n = 176, young adult cohort: n = 1627). Pediatric DTC patients had more frequent adverse baseline features including extrathyroidal extension (p = 0.040), nodal and distant metastases, and American Thyroid Association (ATA) high-risk disease (p < 0.001 each). At two years follow-up post-treatment, young adult DTC patients had significantly lower incomplete responses compared to the pediatric DTC patients (223/1627, 13.7% versus 94/176, 53.4%, respectively, p < 0.001). Over a median follow-up of 10.7 years, 120/1627 (7.4%) young adult DTC patients had recurrent/persistent disease versus 23/176 (13.1%) pediatric DTC patients (p = 0.012). The 10-year DFS probability was 93.6% for the young adult DTCs versus 88.7% for the pediatric DTCs (p = 0.007). ATA high-risk disease and incomplete response at two years were independent predictors of significantly worse DFS in the young adult cohort (p < 0.001 each).

CONCLUSION: Young adult DTCs behave less aggressively compared to their pediatric counterparts with excellent long-term outcomes. Appropriate initial and dynamic risk stratification can help optimize treatment decisions and follow-up strategies.