Objectives: Differentiated thyroid cancer (DTC), encompassing papillary and follicular thyroid carcinomas (FTCs), is the most prevalent endocrine malignancy globally. While prognosis is excellent with early treatment, optimal follow-up strategies remain a subject of ongoing evaluation. Stimulated thyroglobulin (sTg) is a well-established marker for disease surveillance and monitoring. This study analyses the predictive value of sTg in guiding the need for follow-up diagnostic whole-body iodine scan (WBIS) across all risk categories defined by the American Thyroid Association (ATA). Material and Methods: A retrospective single-center study was conducted at a tertiary healthcare center in India, involving postthyroidectomy DTC patients treated with radioactive iodine between June 2020 and November 2024. Patients with complete histopathological data, available sTg and WBIS at 6-month follow-up and negative Tg antibodies status were included in this study. sTg and WBIS results were analyzed across ATA-defined low-, intermediate-, and high-risk groups. Results: A total of 390 DTC patients (71.8% females, with a mean age of 38.5 years) were included in this study, with 94.4% having papillary carcinoma and the rest having FTC. Based on the ATA risk stratification, 31.8% were low-risk, 51.8% intermediate, and 16.4% high-risk. At first follow-up, 163 patients had sTg ≤1 ng/mL, and all had a negative WBIS across all ATA risk categories, yielding a 100% negative predictive value (NPV). Among the 227 patients with sTg >1 ng/mL, 14 (6.17%) had positive WBIS; none of the patients in the low-risk group had a positive WBIS (n = 60). Of 120 patients, 3 (2.5%) in the intermediate-risk group, had a positive WBIS, and 11 of 47 patients in the high-risk group (23.4%) had a positive WBIS. Using the sTg cutoff as 1 ng/mL, sensitivity and NPV were 100%, while specificity and positive predictive value were 43.4% and 6.2%, respectively. Higher sTg correlated with positive WBIS and advanced disease. No recurrences were observed during a median 28-month follow-up period in patients with sTg ≤1 ng/mL. Conclusion: sTg level ≤1 ng/mL with normal Tg antibodies (TgAb) level at follow-up 6-month postradioiodine therapy precisely rules out residual or recurrent disease across all ATA risk categories. WBIS can be avoided at follow-up in patients with sTg ≤1 ng/mL and negative TgAb levels in all risk categories defined by ATA.
Kandula et al. (Tue,) studied this question.
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