Influence of age and primary tumor size on the risk for residual/recurrent well-differentiated thyroid carcinoma

Background. Though age and primary tumor size predict cancer-specific survival in well-differentiated thyroid carcinoma (WDTC), their influence on residual/recurrent disease has not been elucidated. Methods. In a retrospective study, residual/recurrent disease was defined by the surrogate outcome of positive (≥2 lg/L) follow-up stimulated thyroglobulin after surgery and radioactive remnant ablation. Age, primary tumor size, and clinical staging systems were examined in the context of stimulated thyroglobulin outcome. Results. A total of 246 patients were followed up for a mean of 5.8 years. No significant difference in age (t(239) = 0.61, p > .05) or tumor size (t(237) = 0.16, p > .05) was found among patients with positive follow-up stimulated thyroglobulin compared with those with negative results. pTNM staging failed to demonstrate significant, stage-dependent increase in the percentage of patients with positive stimulated thyroglobulin, χ²(2, N = 229) = 0.17, p > .05, unlike staging based solely on surgical pathology, χ²(2, N = 241) = 34.97, p < .001. Conclusion. Age, primary tumor size, and pTNM staging do not predict risk for residual/recurrent WDTC, whereas extrathyroidal extension at initial surgery is predictive.