Clinical evaluation of tumor characteristics predisposing serum thyroglobulin to be undetectable in patients with differentiated thyroid cancer

Abstract

This study delineates tumor characteristics which predispose serum thyroglobulin (TG) to be undetectable in patients in spite of persistent or recurrent differentiated thyroid cancer. Three hundred seventy four thyroid carcinoma patients with completed thyroid ablation were investigated by means of conventional diagnostic procedures (131 iodine total-body scan, x-ray, TG determination) and, in addition, with high-resolution sonographic study of the neck. Sensitivity of TG for the detection of metastases amounted to 83% under TSH stimulation and 50% under thyroxine (T4) treatment. Specificity proved to be 95% under TSH stimulation and 99% under T4 treatment. Common features of the tumors associated with false-negative TG determinations (n = 16) were papillary histologic characteristics, manifestation in lymph nodes of the neck or mediastinum, and small size. It is therefore necessary for the early detection of persistent or recurrent papillary cancer metastases to perform in addition to 131 iodine scans high-resolution sonography of the neck in combination with the determination of TG serum concentrations under endogenous TSH stimulation.

Non-suppressed thyrotropin and elevated thyroglobulin are independent predictors of recurrence in differentiated thyroid carcinoma

“…When on L-T 4 therapy, a consistent level of 2 mg/l during the follow-up period has proved to be highly indicative of the cancer-free state, although only a minority of patients meets this criteria (9). Our cut-off value for serum thyroglobulin level was 3 mg/l, which has also been used in some other studies (7,25,26). In our study, one year after operation, 35 patients (21%) had thyroglobulin over 3 mg/l, of whom 15 (43%) had recurrent disease.…”

“…In our analyses, thyroglobulin values measured during L-T 4 treatment were used. The sensitivity of thyroglobulin measurement decreases but specificity increases compared with values measured when off L-T 4 treatment (25). When on L-T 4 therapy, a consistent level of 2 mg/l during the follow-up period has proved to be highly indicative of the cancer-free state, although only a minority of patients meets this criteria (9).…”

Evaluation and treatment of persistent thyroglobulinemia in patients with well-differentiated thyroid cancer

“…We define persistent thyroglobulinemia as measurable serum Tg in a patient who has had surgical thyroidectomy followed by radioiodine treatment to ablate or treat residual thyroid cancer. Since Tg is increased by TSH stimulation, Tg sensitivity is greater during induced hypothyroidism than while on L-T 4 treatment (5,8,12,(36)(37)(38)(39)(40). Most well-differentiated thyroid cancers display concordance between 131 I uptake (or WBS) and serum Tg.…”

“…Although numerous reports have described alternate imaging procedures for the follow-up of thyroid cancer patients (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), few have assessed the response to therapeutic intervention based on the findings from these images (23).…”

Revisitando a tireoglobulina sérica no seguimento de pacientes com carcinoma diferenciado de tireóide

“…Alguns pacientes podem permanecer com restos tireoidianos normais, mesmo após uma dose terapêutica de iodo 131, que também são estimulados pelo TSH elevado, apresentando Tg detectável mesmo sem doença evidente (2,3,5,7). Além disso, resultados falso-negativos da Tg podem ocorrer em metástases muito pequenas ou linfonodais (3,5,(8)(9)(10)(11)(12)(13). Devemos ressaltar que a propedêutica para os pacientes com Tg detectável geralmente não distingue aqueles com maior probabilidade de metástase distantes daqueles com provável doença cervical apenas, que necessitariam de menor investigação.…”