Unmeasurable Stimulated Thyroglobulin Before Radioactive Iodine Ablation Predicts Excellent Long-Term Outcomes in Patients with Differentiated Thyroid Cancer

Journal article

Background: There is ongoing interest in limiting the extent of treatment for patients with low-risk differentiated thyroid cancer (DTC) and in redesigning individualised follow-up strategies. This study assessed long-term outcomes in patients with excellent response to surgical treatment demonstrated by reaching unmeasurable stimulated thyroglobulin (sTG) levels before proceeding with radioactive iodine ablation. Methods: This is a retrospective cohort study of consecutive patients treated for DTC in a tertiary referral centre. Radioactive iodine ablation (RIA) was done after hormone withdrawal (before 2015) or after Thyrogen stimulation (in recent years). The biochemical assay for TG changed from a lower limit of detectability of 5 ng/mL to 0.2 ng/mL in 2012. Results: Of 331 patients operated on between 2001 and 2019, unmeasurable sTG was measured in 70 of 138 patients (51%) when using an assay with threshold of 5 ng/mL and in 38 of 193 patients (20%) based on the threshold of 0.2 ng/mL. Compared with patients whose sTG was >5 ng/mL, those with sTG <5 ng/mL (187 of 331 patients) were less likely to have T3–T4 tumours or positive lymph node disease (N1a–N1b) and had a lower MACIS score (5.73 ± 1.26 vs. 6.45 ± 1.69, p < 0.001) and much lower mortality with metastatic disease during follow-up for 100 ± 48 months (3/187 vs. 23/144 patients, p = 0.001). Conclusions: Patients with unmeasurable sTG have excellent prognosis, with very low incidence of adverse events. With the wide use of TG assay with a threshold of 0.2 ng/mL (or lower), this subgroup could have patient-initiated follow-up rather than embark on regular assessments.

Authors: Sia, Y; Mihai, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: MDPI
• Journal: Cancers
• Volume: 18
• Issue: 7
• Pages: 1058
• Article number: 1058
• Publication date: 2026-03-25
• Acceptance date: 2026-03-23
• DOI: 10.3390/cancers18071058
• EISSN: 2072-6694
• ISSN: 2072-6694
• Language: English
• Keywords: thyroglobulin; thyroid cancer; recurrence