Empiric 131I treatment of high thyroglobulin levels in differentiated thyroid carcinoma after remnant ablation

Abstract

Aim: The objective of this study is to establish the efficacy of empiric I-131 treatment (EIT) given for patients whose thyroglobulin(Tg) levels remained high after ablative I-131 treatment (AIT). Methods: Fifty-six patients (46 women, 10 men; mean age 47.4±16.8), without distant metastasis, who were treated empirically for high Tg levels after AIT in our clinic, were retrospectively studied. In all patients stimulated Tg levels before AIT (Tg I) and 6 months after AIT (Tg II) were measured. After EIT, post-therapeutic whole-body scintigraphy (PWBS) was performed to all patients. 18F-FDG PET CT was performed to patients who had negative PWBS but continued to have high Tg II levels. Results: PWBS was positive in 28 patients (50%) and negative in 28 patients (50%). Twenty-eight patients did not respond to EIT (50%), and 28 patients (50%) responded to EIT at different rates. Sixteen patients (28.6%) responded to EIT completely, and 12 patients (21.4%) responded to EIT partially. Tg I was 60.7±40 ng/ml and Tg II was 31±20.4 ng/ml in responding patients, whereas Tg I was 87.6±96 ng/ml and Tg II was 114.3±106 ng/ml in unresponding ones. 18F-FDG PET CT was positive in 22 patients and negative in 6. Conclusion: Our findings, suggested that the EIT is not beneficial in patients who have higher Tg II than Tg I and the cure rate is low in increasing Tg levels. The patients who have high Tg II but lower than Tg I can be treated empirically with I-131.