Early Post-operative Stimulated Serum Thyroglobulin: Role in Preventing Unnecessary Radioactive Iodine Treatment in Low to Intermediate Risk Papillary Thyroid Cancer

Abstract

Aim The aims of the study are to evaluate the predictive value of early post-operative stimulated thyroglobulin (sTg) analysis on the recurrence risk, and to define a cut-off value that is related to recurrence risk in low to intermediate risk papillary thyroid cancer (PTC). Methods This retrospective cohort study included individuals who were diagnosed with PTC aged 18 years or older and had been operated by experienced surgeons of a tertiary university hospital between the years 2011 and 2021. The American Thyroid Association thyroid cancer guidelines version 2015 was used as the risk stratification system. Early sTg measurement obtained at 3-4 weeks after surgery when TSH >30 µIU/mL. Data was collected from the hospital database. A total of 328 patients who had post-operative early sTg values with negative anti-Tg antibodies were included. Results The median age was 44 years. Of the 328 patients, 223 (68%) were women. The median tumor diameter was 11 mm. One hundred ninety-one patients (58.2%) had low risk and 137 (41.8%) had intermediate risk for recurrent disease. Of the 328 patients, 4.0% had recurrent disease. In multivariate Cox regression, post-operative early sTg value [OR: 1.070 (1.038-1.116), P = .000], and the pre-operative malign cytology [OR: 1.483 (1.080-2.245), P = .042] were independent risk factors for recurrence. On the ROC curve analysis, the cut-off value of early sTg was 4.1 ng/mL for those with recurrent disease. Conclusion This study demonstrated that early sTg could predict recurrent disease in patients with low to intermediate risk PTC. A cut-off of 4.1 ng/mL was identified with a high negative predictive value.