Recombinant human TSH stimulated thyroglobulin levels at remnant ablation predict structural incomplete response to treatment in patients with differentiated thyroid cancer

In patients with differentiated thyroid cancer, stimulated thyroglobulin (sTg) levels after thyroid hormone withdrawal (THW) at remnant ablation (RA) and at 6 to 12 months are known to have good prognostic value. This study aimed to evaluate the prognostic impacts and best cutoff values of sTg levels under recombinant human thyroid stimulating hormone (rhTSH) treatment at RA and at follow-up. A total of 151 patients were enrolled, of whom 77 were followed up with rhTSH-stimulated Tg (rhTSH-sTg) and 74 with THW-stimulated Tg (THW-sTg) at 6 to 12 months after rhTSH-aided RA. Risk stratification, response to treatment (excellent, indeterminate, biochemical incomplete, and structural incomplete response [SIR]), and clinical outcome were accessed by revised American Thyroid Association (ATA) guideline criteria. Seven out of 151 (4.6%) patients were confirmed to have SIR during the median follow-up of 79.0 months; 3 in the rhTSH group and 4 in the THW group. One hundred thirty-two out of 151 (87.4%) patients were confirmed to have excellent response; 68 (51.5%) in the rhTSH group and 64 (48.5%) in the THW group. The cutoff values of sTg for predicting SIR to treatment at rhTSH-aided RA, THW-sTg, and rhTSH-sTg were 4.64 ng/mL (sensitivity 85.7%, specificity 76.4%, negative predictive value [NPV] 99.2%), 2.41 ng/mL (sensitivity 100%, specificity 94.3%, NPV 100%), and 1.02 ng/mL (sensitivity 66.7%, specificity 94.6%, NPV 98.6%), respectively. sTg levels using rhTSH at both RA and follow-up has a high NPV and are as effective as using THW for predicting SIR. The risk classification according to the revised ATA guidelines can be used effectively to supplement rhTSH-aided sTg levels to predict better clinical outcomes.