Prognostic value of first thyroglobulin in low and intermediate risk patients with follicular differentiated thyroid cancer

Purpose: To define prognostic value of first Tg (fTg) measured after thyroidectomy and just before radio-iodine therapy (RIT), in low/intermediate risk patients and to find optimal threshold of fTg for prediction of incomplete response.Materials and Methods: This is a retrospective study in 383 patients with low/intermediate risk DTC who were treated with surgery followed by risk based administration of 1110-5550MBq of 131I. Response to treatment was assessed 1 and 2 years after RIT. Odds ratio of different risk factors like age, sex, TNM stage, fTg and Anti-Tg Ab were compared between patients with and without incomplete response 1 and 2 years after treatment. Receiver operating curve (ROC) analysis was used for definition of optimal fTg cut off for prognostic purpose.Results: 273 patients (218 female and 55 male) with DTC including 252 PTC and 21 FTC with mean age of 37.5±14.5 years had negative anti-Tg antibody. 86 patients (31.5%) received 1100 MBq of 131I, 70 patients (25.6%): 3700MBq and 117 patients (42.9%): 3700-5550MBq. Using ROC analysis, fTg≥33.5 ng/ml and fTg/TSH ratio of ≥0.36 had the optimal sensitivity and specificity for detection of incomplete response 1 and 2 years after treatment. Multivariate analysis showed that fTg was the most potent risk factor for prediction of treatment failure 1 and 2 years after RIT.Conclusions: FTg was the most important risk factor for prediction of treatment failure after RIT and should be included in decision algorithm regarding RIT or optimal iodine dose determination in low/intermediate risk patients with DTC.

کلیدواژه ها:

Differentiated thyroid cancer ، Thyroglobulin ، Iodine therapy ، Remnant ablation