Title Is there a role for unstimulated thyroglobulin velocity in predicting recurrence in papillary thyroid carcinoma patients with detectable thyroglobulin after radioiodine ablation?

Background. In the follow-up of papillary thyroid cancer (PTC) patients treated with curative thyroidectomy and radioiodine ablation, raised thyroglobulin (Tg) predicts recurrence with reasonable sensitivity and specificity. However, a proportion of patients present with raised Tg level but no other clinical evidence of disease. Only limited data on Tg kinetics have been reported to date. Here we aim to evaluate the prognostic and predictive significance of nonstimulated serum Tg velocity (TgV). Methods. Consecutive PTC patients treated with curative thyroidectomy and radioiodine ablation between 2003 and 2010 were analyzed. Patients with at least one detectable Tg measurement ([0.2 ng/mL) were included. TgV was defined as the annualized rate of Tg change. Logistic regression analyses were performed to evaluate the role of TgV in the prediction of disease recurrence. The optimal TgV cutoff was assigned by receiver–operating characteristic curve analysis. Overall survival of patients above versus below the TgV cutoff were determined by the Kaplan–Meier method and compared. Results. Of a total of 501 patients, 87 had at least one Tg value [0.2 ng/mL; in these latter patients, 29 (33.3 %) developed recurrence. TgV was an independent predictor of the recurrence. TgV C0.3 ng/mL per year predicted recurrence with a sensitivity of 83.3 % and specificity of 94.4 %. Patients with TgV below the cutoff had a significantly better overall survival (p = 0.038). Conclusions. TgV predicts recurrence with high sensitivity and specificity, and is a prognosticator of survival in postthyroidectomy and postablation PTC patients with raised Tg. In papillary thyroid cancer (PTC), thyroidectomy, radioiodine (I) therapy, and thyroid hormone suppression are the mainstay of treatment, conferring excellent overall survival. Despite effective initial treatment, the prognosis is significantly affected by tumor recurrence, which occurs in up to 30 % of patients at 30 years. Improvement of current methods to detect recurrence early and accurately is therefore clinically important. Thyroglobulin (Tg) is a glycoprotein specific to differentiated thyroid tissue; after thyroidectomy and radioiodine remnant ablation, an elevated serum Tg level is a sensitive marker of residual cancer. Periodical measurement of Tg after initial thyroid ablative therapy is recommended in the monitoring of PTC patients. Nevertheless, Tg level may be affected by the various laboratory assays used. Interference may also occur in the presence of anti-Tg antibodies or heterophile antibodies. The sensitivity of Tg can be increased with thyroidstimulating hormone (TSH) stimulated by either thyroid hormone withdrawal or recombinant human TSH Hilda Wong and Kai P. Wong are contributed equally to this article. Electronic supplementary material The online version of this article (doi:10.1245/s10434-012-2391-6) contains supplementary material, which is available to authorized users. The Author(s) 2012. This article is published with open access at Springerlink.com First Received: 8 March 2012; Published Online: 11 May 2012 B. H.-H. Lang, MS e-mail: [email protected] Ann Surg Oncol (2012) 19:3479–3485 DOI 10.1245/s10434-012-2391-6