OP17 – Early Thyroglobulin Measurement and Response to Therapy in Patients with Differentiated Thyroid Cancer

      Guerra, J.L1; Brenzoni P2; Posadas, S2; Voogd, A.I3; Begueri, Buquet A.3; Valdez P3, Russier, G.3; Rojas, M.2; Saco, P.3; Negueruela, M.C.1 1 Division of Endocrinology, Hospital Universitario Austral, Buenos Aires, Argentina 2 Laboratory of Endocrinology, Hospital Universitario Austral, Buenos Aires, Argentina 3 Head and Neck Surgery Department, Hospital Universitario Austral, Buenos Aires, Argentina Background: Serum Thyroglobulin (Tg) is a biomarker of persistent or recurrent disease in Differentiated Thyroid Carcinoma (DTC) follow-up. Highly sensitive Tg (hsTg) assays with improved functional sensitivity (FS) allows detection of low Tg concentrations. Objective: To evaluate the association between early hsTg levels and response to therapy. Subjects and Methods: An observational retrospective study was performed on 99 patients with DTC who underwent total thyroidectomy (TT). We evaluated hsTg at 6?8 weeks in Low, Intermediate and High Risk of Recurrence tumours as well as clinical implications of response to therapy. Tg measurement was performed in the absence of anti-Tg antibodies using an electrochemiluminescence highly sensitive assay (FS: 0.1 ng/ml), both on levothyroxine therapy or with thyroid hormone withdrawal. Statistical analysis was performed to correlate hsTg levels with response to therapy. Results: Results show a statistically significant association between early hsTg levels and response to therapy using both t test and Mann-Whitney test, since, as expected, the distribution of Tg values was right skewed. Logistic regression analysis shows an increasing probability of worse response with higher serum hsTg. ROC curve revealed that using a hsTg of 2.5 ng/ml as a cut off, specificity and sensibility to predict worse response to therapy were 88.5 and 58.3 %, respectively (AUC: 0.77, CI 95%: 0.57-0.96). Discussion and Conclusions: Early hsTg measurement at 6-8 weeks after TT could be useful to identify patients at higher risk of recurrence at the beginning of treatment, allowing physicians to observe closely for those with suspected worse prognosis. References:
    1. Rosario P, Flávio A, Filho C. Does undetectable basal Tg measured with a highly sensitive assay in the absence of antibodies and combined with normal ultrasonography ensure the absence of disease in patients treated for thyroid carcinoma? Arq Bras EndocrinolMetab. 2012:56/2.149-151.
    2. Carole Spencer, Jonathan LoPresti and Shireen FatemibHow. Sensitive (second-generation) thyroglobulin measurement is changing paradigms for monitoring patients with differentiated thyroid cancer, in the absence or presence of thyroglobulin autoantibodies. Curr Opin Endocrinol Diabetes Obes. 2014 Oct; 21(5): 394–404.
    3. Prognostic value of serial serum thyroglobulin determinations after total thyroidectomy for differentiated thyroid cancer. N. Lima, H. Cavaliere, E. Tomimori, M. Knobel, and G. Medeiros-Neto Thyroid Unit, Endocrine Division, University of Sao Paulo Medical School, São Paulo, Brazil. J. Endocrinol. Invest. 25: 110-115, 2002.,August 2011, 118-122.


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