Predictors of success of the ablative/therapeutic radioiodine (131I) in differentiated thyroid cancer

Introduction:Differentiatedthyroid carcinoma (DTC) constitute approximately 90% of all thyroid tumors with an overall excellent prognosis. However, there is a small group of patients with a more aggressive form of disease, usually associated with certain poor prognostic factors. Using our large database of patients with DTC, the current study aims at identifying some of these factors.  Methods:This retrospective study was based on the registry of patients with non-medullary thyroid carcinoma. Data were collected on the clinical, laboratory, and outcome characteristics of 501 patients followed at our department. Results: On multivariate analysis, the following variables were predictive of persistent disease: less than total thyroidectomy, residual disease on the post treatment whole body radioiodine scan (WBIS), higher received radioiodine activities, and higher levels of baseline stimulated thyroglobulin (Tg) and thyroid stimulating hormone (TSH). The greatest predictive value for the persistent/recurrent disease was attributed to the presence of residual disease on the post-treatment WBIS (odds ratio (OR): 33.72, 95% confidence interval (95% CI): 18.17-62.57), followed by type of surgical procedure (OR: 8.92, 95% CI: 2.90-27.39), radioiodine ablation dose (OR: 4.03, 95% CI: 1.56-10.39), stimulated baseline Tg level (OR: 2.79, 95% CI: 1.53-5.08) and finally, the stimulated baseline TSH level (OR: 2.21, 95% CI: 1.08-4.519). Conclusion: In patients with DTCs, surgical procedures other than total thyroidectomy, presence of residual disease on the post-treatment WBIS, higher received radioiodine activities, higher baseline stimulated Tg and TSH levels are associated with a higher probability of having persistent disease and can be used in conjunction with other disease characteristics to reach proper decisions with regard to treatment and follow-up.