Thyroid Biology and Disease

MON-398 - Real-World Comparison of 2015 and 2025 American Thyroid Association Risk Stratification Systems for Recurrence in Differentiated Thyroid Cancer

Monday, June 15, 2026

9:00 AM - 2:00 PM CT

Late-Breaking Poster Presenter(s)

IS

Irem Sonmezoglu Kutuk, MD

Dr.
Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey

Co-Author(s)

YE

Yagmur Eken, MD

Gazi University Faculty of Medicine, Department of Internal Medicine
Ankara, Turkey
SA

Sabri Engin Altintop, MD

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
AG

Arif Cengiz Gultekin, MD

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
EC

Ethem Turgay Cerit, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
AE

Alev Eroglu Altinova, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
MA

Mujde Akturk, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
FT

Fusun Toruner, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
MK

Mehmet Ayhan Karakoc, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey
MY

Mehmet Muhittin Yalcin, Prof. Dr.

Gazi University Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology and Metabolism
Ankara, Turkey

Background
Risk stratification is essential for guiding management in differentiated thyroid cancer (DTC). The ATA 2025 system introduces a more refined classification compared to ATA 2015, particularly within intermediate-risk categories. However, real-world data evaluating its clinical implications remain limited.

Methods
We retrospectively analyzed 313 patients with DTC who underwent surgery between 2015 and 2022. Recurrence risk was classified according to ATA 2015 and ATA 2025 systems. Baseline clinicopathological features, reclassification patterns, and distribution of radioactive iodine (RAI) therapy were evaluated. Survival analyses were performed in 255 patients with at least 24 months of follow-up. Cox regression and ROC analyses were used to assess the association of each classification system with recurrence.

Results
The median age was 48 years (IQR 38–57), and 80.2% of patients were female. RAI therapy was administered in 53.7% of the cohort. Median follow-up duration was 64 months (IQR 38.5–91).
Reclassification according to ATA 2025 demonstrated substantial heterogeneity within ATA 2015 risk groups. While most ATA 2015 low-risk patients remained low risk, a subset was reclassified into higher-risk categories.
Similarly, ATA 2015 intermediate-risk patients were redistributed across low–intermediate, intermediate–high, and high-risk groups. Across the cohort, recurrence rates increased progressively with higher ATA 2025 risk categories.
RAI administration was more frequent in higher-risk groups; however, recurrence persisted in intermediate–high and high-risk patients despite RAI. In contrast, recurrence rates were low and similar between RAI-treated and untreated patients in the ATA 2025 low-risk group.
Among ATA 2015 low-risk patients who received RAI, 39.1% were reclassified into higher ATA 2025 categories. Notably, no recurrences were observed in the low–intermediate and intermediate–high subgroups receiving RAI.
In univariate Cox analysis, both ATA 2015 (HR 3.82, 95% CI 2.22–6.58, p< 0.001) and ATA 2025 (HR 3.14, 95% CI 2.03–4.86, p< 0.001) were significantly associated with recurrence. ROC analysis demonstrated an AUC of 0.790 for ATA 2015 and 0.825 for ATA 2025.

Conclusions
ATA 2025 provides improved risk stratification within ATA 2015 categories by identifying clinically meaningful subgroups with distinct recurrence risks. Although some patients classified as low risk according to ATA 2015 received RAI, many of these patients were reclassified into higher-risk categories under ATA 2025. This pattern suggests that RAI administration in real-world practice may reflect appropriate clinical judgment, with clinicians selectively treating patients with higher underlying risk not fully captured by ATA 2015 classification. Nevertheless, longer-term follow-up is needed to better define recurrence outcomes.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*