The Prognostic Impact of Tumor Size in Papillary Thyroid Carcinoma is Modified by Age

Background: Although the importance of tumor size in papillary thyroid cancer (PTC) is well established, there is no research investigating whether age modifies the impact of tumor size, and there is conflicting evidence regarding optimal size thresholds for prognostic discrimination. We aimed to verify that tumor size is an independent prognostic factor in PTC, investigate the impact of patient age, and identify optimal size cutoffs for risk stratification using objective measures of model performance. Methods: A retrospective analysis of 574 patients with PTC, using multivariate Cox regression models to test the impact of tumor size on recurrence-free survival (RFS). Subgroup analyses were performed in patients aged <55 and ≥55 years. Exploratory analyses to identify optimal size cutoffs for prognostic discrimination were performed using the proportion of variation explained (PVE) and Harrell's C-index. Results: Tumor size predicted RFS on multivariate analysis in the overall study cohort (hazard ratio ...