Follicular Thyroid Carcinoma: Disease Response Evaluation Using American Thyroid Association Risk Assessment Guidelines

Objective: To evaluate the overall and progression-free survival for follicular thyroid carcinoma (FTC) based on the American Thyroid Association (ATA) staging system for recurrence risk assessment and the TNM staging system. Methods: A clinical review of FTC patients between 1995 and 2014 was conducted at a single center. The data was classified using the TNM staging system into low, intermediate, and high risk of recurrence as per the ATA risk assessment. Results: Over the course of 19 years, 114 (11.9%) of all of the thyroid cancer patients presenting to our hospital had FTC (i.e. 78 females and 36 males). The age range was 15-80 years. Ninety-four tumors were resectable and 18 were unresectable. Sixteen patients were excluded due to insufficient information on their recurrence risk. Based on the ATA categorization, 36 patients had a low recurrence risk. All patients were alive at the time of categorization, and 1 showed progressive disease. Thirty-eight patients had an intermediate recurrence risk. One patient died and 2 showed progression. Twenty-four had a high recurrence risk. Seven patients died and 6 showed progression. In terms of TNM stages, 2 (3.2%) stage I, 3 (17.6%) stage II, 1 (14%) stage III, and 2 (12.5%) stage IV patients died during follow-up. Both ATA risk classification and TNM staging were significant predictors of disease-free survival. On bivariate analysis, the ATA classification (HR  4.67; 95% CI 1.74-12.5, p  =  0.002) was a better predictor of survival compared to the TNM classification (HR 1.26; 95% CI 0.98-1.62, p = 0.063). Conclusion: ATA risk stratification predicts the disease recurrence rate and survival better than TNM staging. Age does not have an association; the risk category with dynamic reassessment effectively better predicts the course of disease in FTC.