Preablation Stimulated Thyroglobulin Is a Good Predictor of Successful Ablation in Patients With Differentiated Thyroid Cancer

Purpose: To evaluate the predictive capacity of clinical and laboratory variables in relation to the success of ablation. The variables studied were as follows: thyroglobulin (Tg) in hypothyroidism, before ablation; age; gender; type of carcinoma (papillary or follicular); the tumor stage; the administered activity of I-131; and the whole-body scan 7 days after ablation. Materials and Methods: Retrospective review of the medical records of all patients who were admitted to the therapeutic room to undergo treatment with I-131, from 1998 to 2007. Of the records reviewed, 96 patients fulfilled the inclusion criteria and had no exclusion criteria. A negative whole-body scan and Tg in hypothyroidism <2 ng/mL, after 6 to 12 months of treatment, were considered as successful ablation. Results: The dosage of Tg in hypothyroidism, measured before the ablation, was the only independent predictor of ablation success in multivariate analysis (P < 0.0001), and the optimal cutoff for this cohort was 18 ng/mL. On univariate analysis, the high-risk staging was predictor of ablation failure. Conclusion: The measurement of Tg in hypothyroidism before ablation might be useful if added to the routine evaluation of patients before I-131 treatment because it was a good predictor of successful ablation.