Prognostic value of postsurgical stimulated thyroglobulin levels after initial radioactive iodine therapy in well‐differentiated thyroid carcinoma

BACKGROUND: In well-differentiated thyroid carcinoma, predictors of future positivity of stimulated thyroglobulin (>2 microg/L) after initial radioactive iodine treatment are not known. METHODS: In a retrospective study, we used logistic regression analysis to determine whether postoperative stimulated thyroglobulin measurements and pathologic stage independently predict future stimulated thyroglobulin positivity. RESULTS: We followed 141 patients with well-differentiated thyroid carcinoma for a median of 35 months; follow-up stimulated thyroglobulin measurements were positive in 20.6% (29/141). The natural logarithm of the postsurgical stimulated thyrogolobulin was independently associated with a positive stimulated thyroglobulin at long-term follow-up (odds ratio [OR], 4.44; 95% confidence interval [CI], 2.33-8.45; p < .001); there was a trend for a positive association of TNM stage with positive follow-up stimulated thyroglobulin (p = .054). Lymph node positivity predicted a positive stimulated thyroglobulin in papillary cancer. CONCLUSIONS: Stimulated thyroglobulin measurements prior to initial radioactive iodine treatment independently predict future stimulated thyroglobulin positivity in well-differentiated thyroid carcinoma.