Factors Affecting Disease-Free Status of Differentiated Thyroid Carcinoma Patients

Purpose: The study aim was to assess factors that impact on the outcome of radioiodine therapy in patients diagnosed with differentiated thyroid carcinoma (DTC). Materials and Methods: We performed a retrospective cohort study on 256 patients with DTC who underwent thyroidectomy and received radioiodine therapy during December 2003 to January 2012. All patients were followed up for at least 1 year. They were considered diseasefree by the criteria of the revised American Thyroid Association Management Guideline for Patients with Thyroid nodules and DTC (ATA guideline 2009). Results: On Cox univariate analysis, factors associated with disease-free status were age<45, stage I tumor, low risk group by histopathology, unifocal tumor involvement, stimulated serum Tg level at 1st dose of radioiodine therapy and no distant metastasis from 1st post-treatment WBS (post RxWBS). On multivariate analysis, stage I tumor and stimulated serum Tg level at 1st dose of radioiodine therapy < 30 ng/mL were the significant prognostic factors that increased disease-free rate by 1.73 times and 2.60 times, respectively (P-value <0.05). Conclusions: Factors affecting the outcome of radioiodine therapy in our study were age, stage, risk of recurrence by histopathology, unifocal tumor involvement and 1st postRxWBS findings. From these factors, stage I tumor and stimulated serum Tg level at 1st dose of radioiodine therapy were independent prognostic factors that substantial increase the disease-free rate.