Highlights
The 2025 ATA risk stratification system for papillary thyroid carcinoma (PTC) demonstrates significant reclassification patterns when applied to a real-world cohort of 670 patients. Low-risk classifications decreased by 22.2%, while intermediate and high-risk categories increased by 41.7% and 14.9% respectively. The newly defined “low-intermediate-risk” class represents a statistically distinct group with structural disease persistence risk falling between prior low-risk and intermediate-risk categories.
Background
Papillary thyroid carcinoma represents the most common histological subtype of thyroid cancer, accounting for approximately 80-85% of all thyroid malignancies. Over the past decade, the management of PTC has evolved substantially, with risk stratification systems playing a pivotal role in guiding treatment decisions, including the extent of surgery, radioactive iodine ablation, and long-term surveillance strategies.
The American Thyroid Association (ATA) guidelines have historically provided the most widely adopted risk stratification framework for differentiated thyroid cancer. The 2015 ATA risk stratification system classified patients into low-risk, intermediate-risk, and high-risk categories based on clinicopathological features, establishing evidence-based recommendations for initial management and follow-up protocols. However, emerging data regarding prognostic factors and clinical outcomes necessitated a comprehensive revision of these classification criteria.
The 2025 ATA guidelines introduced an updated risk stratification system that modifies several key parameters, including the classification of certain pathological features and the introduction of more granular risk categories. While these revisions were developed through expert consensus and systematic literature review, validation in independent patient cohorts remained essential before widespread clinical adoption.
Study Design
This retrospective observational study was conducted at a single tertiary care center with specialized thyroid oncology services. The research team identified 670 patients with confirmed papillary thyroid carcinoma who had complete histopathological documentation and documented final disease outcomes available for analysis.
Patients were classified according to both the 2015 and 2025 ATA risk stratification systems to enable direct comparison. The primary outcome measure was structural disease persistence, defined as the presence of persistent or recurrent structural disease documented through imaging studies, biochemical markers, or histological confirmation during follow-up.
Cross-comparison analyses were performed to evaluate how individual patients were redistributed between risk categories and to assess the predictive validity of the new classification system for disease outcomes.
Key Findings
Reclassification Patterns
Application of the 2025 ATA risk stratification system to the study cohort revealed substantial shifts in risk classification compared to the 2015 system. The proportion of patients classified as “low-risk” decreased by 22.2%, representing a significant migration of patients into higher-risk categories. Conversely, the “intermediate-risk” classification increased by 41.7%, while “high-risk” classification increased by 14.9%.
This redistribution pattern suggests that the 2025 criteria apply more stringent thresholds for defining low-risk disease, potentially incorporating additional factors that incrementally increase the perceived risk of structural disease persistence.
Structural Disease Persistence by Risk Category
Cross-comparison between the two stratification systems demonstrated that structural disease persistence rates in the 2025 “low-risk” and “high-risk” classes were broadly comparable to their 2015 counterparts. This finding suggests that the extreme ends of the risk spectrum maintain reasonable predictive validity across both classification systems.
The 2025 “intermediate-high-risk” class demonstrated similar structural disease persistence characteristics to the former “intermediate-risk” class, indicating reasonable continuity in risk prediction for this category.
The Emergence of the Low-Intermediate-Risk Category
The most clinically significant finding was the identification of a new “low-intermediate-risk” class in the 2025 system. This category had no direct equivalent in the 2015 stratification and emerged as a distinct prognostic entity. Patients classified in this group demonstrated a risk of structural disease persistence that was statistically higher than the 2015 “low-risk” class (p = 0.003) but lower than the 2015 “intermediate-risk” class (p = 0.012).
This intermediate positioning suggests that the low-intermediate-risk category captures a clinically meaningful subset of patients whose outcomes differ from both traditional low-risk and intermediate-risk populations. The statistical significance of these comparisons (p < 0.05) indicates that this distinction is not merely theoretical but reflects genuine differences in disease behavior.
Expert Commentary
The validation study provides crucial real-world evidence regarding the performance of the updated ATA risk stratification system. Several methodological strengths enhance the credibility of these findings: the inclusion of patients with complete histopathological and outcome data, the use of final disease outcome as the endpoint rather than surrogate markers, and the direct comparison between classification systems in the same patient population.
However, several limitations warrant consideration when interpreting these results. The single-center, retrospective design introduces potential selection bias, and the cohort may not fully represent the spectrum of disease severity encountered in diverse clinical settings. Additionally, the specific institutional protocols for initial treatment and follow-up surveillance may influence observed outcome rates, potentially limiting generalizability to centers with different management approaches.
The emergence of the low-intermediate-risk category as a distinct prognostic group carries important implications for clinical practice. This finding suggests that the 2025 guidelines may have more precisely stratified patient risk, particularly in the previously heterogeneous intermediate-risk population. However, the optimal management strategy for patients in this new category remains undefined, as clinical trials and prospective studies specifically addressing this group have not been conducted.
The shift toward higher-risk classifications observed in this cohort has practical implications for clinical decision-making. More patients may qualify for radioactive iodine ablation, more intensive initial surveillance protocols, and longer duration of follow-up. Healthcare systems should anticipate increased resource utilization and adjust clinical pathways accordingly.
Conclusion
This validation study confirms that the 2025 ATA risk stratification system produces meaningful reclassification of papillary thyroid carcinoma patients compared to the 2015 system, with a substantial proportion of patients migrating to higher-risk categories. The structural disease persistence rates in the extreme risk categories remain comparable between systems, supporting the continued validity of core risk stratification principles.
The identification of the low-intermediate-risk category as a distinct prognostic entity represents the most significant finding for clinical practice. This newly defined group requires dedicated prospective studies to establish evidence-based management recommendations, including decisions regarding radioactive iodine therapy, intensity of surveillance, and counseling regarding prognosis.
Clinicians caring for patients with papillary thyroid carcinoma should be aware of these classification changes when applying the 2025 ATA guidelines. The validation in a real-world cohort provides reassurance regarding the system’s predictive properties while highlighting areas requiring further investigation.
References
Moneta C, Trevisan M, Colombo C, De Luca A, Lugaresi M, Reali GM, Gazzano G, Persani L, Fugazzola L, De Leo S. VALIDATION OF THE 2025 ATA RISK STRATIFICATION SYSTEM IN A COHORT OF PATIENTS WITH PAPILLARY THYROID CARCINOMA. The Journal of clinical endocrinology and metabolism. 2026-04-17. PMID: 41994857.