Role of FDG PET-CT in Differentiated Thyroid Carcinoma; Case series & Focus on ATA 2025 Guidelines

Abstract

Background:   Fluorodeoxyglucose positron emission tomographyâ€"computed tomography has become an essential imaging technique in modern oncology and plays an important role in the evaluation of Well-differentiated thyroid cancer. Current 2025 ATA guidelines have made the role of FDG PET/CT in differentiated thyroid cancer more nuanced and clinically meaningful. It has placed the role of FDG PET in a wider clinical context while keeping previous indication. It is now considered earlier in evaluation of patients with recurrent or persistent disease, and its findings not only help in localization of disease but also provide meaningful insight regarding tumor biology and aggressiveness. Objective:   To evaluate the role of FDG PET/CT scan in well differentiated thyroid carcinoma earlier in the disease course.   Methods:   18F-FDG PET/CT of 03 patients with differentiated thyroid cancer (one with follicular, second with poorly well differantiated and third patient with suspected papillary thyroid carcinoma) were retrospectively evaluated.      Discussion: Thyroid cancer is the most common endocrine malignancy, ranking 7th globally and 2nd in people under 40 (GLOBOCAN 2022). Standard imaging includes ultrasound, radio-iodine scans, CT/MRI, and FDG PET/CT. The 2025 ATA guidelines expand FDG PET/CT use for earlier evaluation of recurrent/persistent disease, providing insights into tumor biology, aggressiveness, and prognosis. It is also useful in patients with undetectable Tg but persistent TgAbs. Conclusion:   Importantly, despite this expanded role, FDG-PET/CT is still not recommended for routine initial imaging. Overall evolution from 2015 to 2025 reflects a gradual but important transition from using FDG-PET/CT when radioiodine imaging fails to integrating it earlier as a part of more personalized, risk adapted approach to patient management.