Outcome of Patients With Differentiated Thyroid Cancer Treated With 131-Iodine on the Basis of a Detectable Serum Thyroglobulin Level After Initial Treatment

Background: In patients with differentiated thyroid cancer (DTC) and raising serum thyroglobulin (Tg) after total or near-total thyroidectomy and (131)I remnant ablation an empiric (131)I therapy may be considered. However, outcome data after empiric therapy in did not show a clear evidence of improved survival. We assessed the efficacy of such empiric (131)I therapy in patients with DTC and evaluated the long-term outcome. Methods: A total of 100 patients with DTC showing raised Tg level during follow-up after thyroidectomy and (131)I ablation were treated with a further (131)I therapy (6.1 ± 1.7 GBq). Whole-body scan (WBS) was performed 5–7 days after therapy. Tg value at 12 months after (131)I therapy was considered as an indicator of treatment response: ≤1.5 ng/ml complete remission (CR), >50% decrease partial remission (PR), higher than pre-therapy progression disease (PD), all other cases stable disease (SD). Patients were followed-up for 96 ± 75 months. Results: After 12 months, 62% of patients were in CR, 16% in PR, 8% in SD, and 14% in PD. WBS was positive in 41% of patients and negative in 59% (P = NS). Among patients with local recurrences at WBS 89% showed either CR or PR, while 71% of patients with distant metastases were in SD or PD (P < 0.001). Distant metastases at WBS (P < 0.05), CR (P < 0.0001), and CR + PR (P < 0.0001) were predictors of both progression free survival and overall survival. Conclusion: There is a beneficial effect of (131)I therapy on outcome of patients with DTC treated on the basis of elevated Tg value. In these patients, survival is affected by achievement of CR or PR at 12 months evaluation after (131)I therapy and by the presence of distant metastases at WBS.