Photo Credit: AlexRaths

The following is a summary of “Limited Utility of Routine Surveillance Ultrasound in Differentiated Thyroid Cancer Patients With Undetectable Postoperative Thyroglobulin Levels,” published in the January 2025 issue of Endocrinology by Seo et al. 

Neck ultrasound (US) and serum thyroglobulin (Tg) measurements currently serve as the primary modalities for long-term surveillance of differentiated thyroid cancer (DTC).  

Researchers conducted a retrospective study to analyze the utility of neck US in patients with DTC who underwent total thyroidectomy and had undetectable Tg.  

They analyzed patients with DTC who underwent total thyroidectomy between 2010 and 2023 at institution and received ultrasound-guided fine needle aspiration (FNA) during surveillance. Patients were grouped based on Tg and Tg antibody (Tg Ab) status before biopsy:  ‘Negative Tg’ for undetectable Tg (<0.2 ng/dL) and Tg Ab, ‘Positive Tg’ for detectable Tg and undetectable Tg Ab, and ‘Positive Tg Ab’ for detectable Tg Ab. The positive predictive value (PPV) of neck US was calculated by defining ‘true positive’ as findings prompting FNA resulting in DTC and ‘false positive’ as findings prompting FNA not resulting in DTC.  

The results showed 118 patients underwent 146 FNA biopsies 33 (23%) were Negative Tg, 84 (57%) were positive Tg, and 29 (20%) were positive Tg Ab prior to biopsy. The PPV of neck US was 3% (1 true positive, 32 false positives) for Negative Tg, 52% (15 true positives, 14 false positives) for Positive Tg Ab and 50% (42 true positives, 42 false positives) for Positive Tg. Sub-analysis of the Positive Tg group revealed a PPV of 29% at detectable serum Tg of 0.2 ng/dL, 38% for Tg <1.0 ng/dL, and 58% for Tg ≥1 ng/dL.  

Investigators concluded that, due to the low PPV of neck US and the availability of ultra-sensitive serum Tg measurements, future guidelines should reduce routine neck US management in patients with undetectable serum Tg and only conduct it when serum Tg levels rise. 

Source: onlinelibrary.wiley.com/doi/abs/10.1111/cen.15198