Purpose: Little is known about prognostic factors and treatment outcomes in young patients with anaplastic thyroid cancer (ATC). The goal of this study is to define the clinical features of this subgroup. Material and methods: Patients age 55 or younger with either ATC or well-differentiated thyroid cancer (WDTC) with anaplastic changes were identified using electronic medical record at the Cleveland Clinic. The same number of patients older than 55 was randomly selected to serve as control. Progression-free survival (PFS), overall survival time (OST) and cause-specific mortality (CSM) were measured against age, tumor histology, extent of disease, and treatment modalities. Results: Twelve patients age 55 or younger were identified. The median age was 51 years. Four patients had WDTC with anaplastic components - mixed tumor group (MTG). Their median PFS, OST, and CSM at 24 months were 21.5 months, 51 months, and 25%, respectively. For the other 8 patients who had pure ATC, their median PFS, OST, and CSM were 3.5 months, 6 months, and 100%, respectively. Patients in the MTG had better survival compared to the pure ATC and control group in terms of PFS (p = 0.0047 and p = 0.0053), OST (p = 0.0028 and p = 0.0029) and the CSM at 24 months (p = 0.0339 and p = 0.0096). In the pure ATC group, patients with positive cervical lymph node and distant metastases had similar overall survival outcomes (6 vs. 8 months, p = 0.4995). Conclusion: Prognostic factors favoring survival in young patients with ATC include ATC arising within WDTC. Once full anaplastic transformation occurs, age was not a significant factor in survival.
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