Positive predictive value of detectable stimulated tg during the first year after therapy of thyroid cancer and the...

This study evaluated the positive predictive value (PPV) of detectable stimulated thyroglobulin during the first year after treatment of thyroid carcinoma (Tg-1) and the value of comparison with Tg-ablation and measured after 24 months (Tg-2). Forty-two consecutive patients undergoing total thyroidectomy and ablation with detectable Tg-1 (>1ng/mL) were selected. The patients had well-differentiated tumors, which were completely resected, and there was no ectopic uptake on whole body scan after 3.7-5.5GBq I(131). Imaging methods during follow-up revealed metastases in 10 patients (24%) (15% if Tg-1 10 ng=mL). Tg-ablation (cutoff of 10 ng/mL) presented a negative predictive value (NPV) of 91% and PPV of 42%. Comparing Tg-ablation with Tg-1, the PPV of an increase was 100%, whereas the NPV of a decrease was 88%. Thirty-six patients presented negative imaging results upon first assessment and Tg-1 was compared to Tg-2. Metastases were detected in all patients who presented an increase in Tg (n=4), whereas patients without variation (n=4) or with a decrease (n=28) showed no apparent disease. Among disease-free patients (n=32), 50% presented undetectable Tg and 40% showed a >50% decrease after 2 years. In conclusion, most patients with detectable stimulated Tg during the first year after therapy had no metastases, and evaluation of the slope of Tg helped discriminate cases with apparent disease.