Abstract Disclosure: H. Gondaliya: None. N. Nangadda: None. D. Bhat: None. K.S. Khadilkar: None. S. Kumbenahalli Siddegowda: None. B.G. Sooragonda: None. A. Shetty: None. S. Kannan: None. In ATA risk stratification system for differentiated thyroid cancer (DTC), one of the variables placing patients in ATA high risk category is thyroglobulin (Tg) suggestive of distant metastases. However there is no defined cut-off Tg level for guiding the clinicians. We aimed to determine pre-ablative stimulated Tg (psTg) value that predicts ATA high risk patients (based on non-Tg parameters) and their treatment response on follow up. This was an ambispective observational study of 285 patients with DTC treated at our centre from April 2017 to November 2022. psTg was measured in all patients 3-4 weeks after surgery and they were subjected to RAIA depending on clinician’s discretion and followed up using the ATA dynamic risk stratification every 6 months. The cohort was divided into two groups: ATA high risk and ATA non-high risk (Low and intermediate risk). Patients among high risk group were divided based on response to treatment into structural incomplete group and non-structural incomplete group (Excellent, Indeterminate and Biochemically incomplete response). The mean age of the study population was 41±15 years and 68% (n=194) were female and 87% (n=249) were papillary thyroid cancer (PTC) and 13% (n=36) were Follicular Thyroid Cancer (FTC). Median duration of follow up was 2.95 years (IQR: 1.42 - 5.12). Among those with PTC, 75% were Classic, 15% Follicular variant and 10% aggressive variants that included tall cell, hobnail, diffuse sclerosing and columnar variant. On ATA risk stratification, 81.75% (n=233) patients were in non-high risk group with median psTg 3.4 ng/ml (IQR 0.5-12.2) and 18.25% (n=52) were in high-risk group with median psTg 150.5 ng/ml (IQR 7.15-439.5). On ROC analysis of all the patients, a psTg value >53.3 ng/ml was predictive of ATA high risk group with PPV of 64%; NPV of 93.5% and AUC 0.81. In ATA high-risk group, there were 73% (n=38) of patients with structural incomplete response on follow up and their median psTg was 287 ng/ml (IQR 95-500) and there were 27% (n=14) with non-structural incomplete response and their median psTg level of 6.2 ng/ml (IQR 2.3-110). A psTg value >53 ng/ml discriminated structural incomplete from non-structural incomplete response with PPV of 77%; NPV 87% and AUC 0.83. A psTg value >53 ng/ml not only predicts ATA high risk patients but also indicates those who are likely to remain with structural residual disease at follow up of 3 years. Presentation: 6/1/2024
Read full abstract