Basal or stimulated thyroglobulin in the assessment of response to therapy in papillary thyroid Carcinoma? A retrospective cohort study

Abstract

The response to initial therapy is an excellent tool for monitoring papillary thyroid carcinomas (PTC) and uses, among other tests, serum thyroglobulin (Tg) measurement, the main marker for detecting persistence/recurrence of the disease. Although the Tg measurement is sensitized by the presence of high TSH concentration, still isn't clear if the response of initial therapy is best rated by the measurement of Tg under levothyroxine (TgB) or in the absence of medication, that is, Tg stimulated by elevated TSH (TgS). Objectives: Evaluate, in patients treated with TT and ¹³¹I if the therapy response changes 1 year after initial therapy, using TgS in relation to TgB. Once observed this change, there'll be an evaluation of which answer- obtained with TgB or TgS - better represents the cases evolution. Methods: This is a retrospective observational cohort study with patients with PTC undergoing therapy (TT + 131I). The main variable of interest will be the response obtained 1 year after the initial therapy, classified as excellent, incomplete and undetermined biochemistry, according only to TgB and TgS. The main outcome considered will be the percentage of cases that had altered their response to therapy, evaluated 1 year after the initial treatment (TT + ¹³¹I), as a function of TgS in relation to TgB. Also considered is the evolution of cases (clinical status of patients in the last evaluation: excellent response, incomplete biochemistry, incomplete structural and undetermined) and disease-free survival time (time under excellent response); in addition to other clinical and laboratory parameters. (AU)