Comparative evaluation of dynamic risk stratification according to ATA 2015 and ATA 2025 in low-risk differentiated thyroid cancer without radioiodine ablation

TL;DR

This study compares two risk stratification methods for low-risk thyroid cancer patients not receiving radioiodine treatment, finding that the newer method classifies more patients as having an excellent response.

Contribution

The study evaluates the impact of updated 2025 ATA criteria on risk stratification in low-risk thyroid cancer patients without radioiodine ablation.

Findings

ATA2025 criteria significantly increased excellent response rates compared to ATA2015-M.

An intermediate thyroglobulin cutoff of 1 ng/mL provided a more realistic response classification.

Anti-thyroglobulin antibody negativization was the main driver for reclassification under ATA2025.

Abstract

To compare dynamic risk stratification (DRS) according to the 2015 American Thyroid Association-Momesso et al. 2016 extension (ATA2015-M) and the 2025 ATA update in low-risk differentiated thyroid cancer (DTC) managed without radioactive iodine (I-131), and to explore the role of an intermediate thyroglobulin (Tg) cutoff of 1 ng/mL.

We conducted a retrospective analysis of a prospectively collected cohort of 74 low-risk DTC patients treated with total thyroidectomy (n = 55) or hemithyroidectomy (n = 19) between 2020 and 2024. Clinical, histopathological, and biochemical data were collected. DRS was assessed at the first follow-up visit (6 months after surgery) and at the last visit (median follow-up 27 months [IQR 16–41]) using ATA2015-M and ATA2025 criteria. An exploratory analysis applying a Tg cutoff of 1 ng/mL was performed.

According to ATA2015-M, excellent response (ER) rates in total thyroidectomy patients increased from 49.2% at baseline to 52.8% at final follow-up. In contrast, ATA2025 classified 89.1% as ER at baseline and 98.2% at final follow-up (p < 0.001). Using the intermediate cutoff of 1 ng/mL, ER rates were 80.0% and 89.1%, respectively. Reclassification to ER under ATA2025 was primarily driven by anti-thyroglobulin antibody (TgAb) negativization, as Tg values remained stable and below the new 2.5 ng/mL threshold. No structural incomplete responses were observed.

ATA2025 criteria substantially increase ER classification in low-risk DTC patients managed without I-131 compared with ATA2015-M. A 1 ng/mL Tg cutoff may provide a more realistic representation of clinical practice. The dynamic trend of TgAb, rather than their presence alone, is a key determinant for reclassification during follow-up.

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