Serum thyroglobulin in the follow-up of patients with treated differentiated thyroid cancer.

Abstract

To determine the significance of serum thyroglobulin (Tg) level in terms of presence or absence of thyroid cancer, we evaluated available serum Tg data on and off T4 therapy in 180 patients with differentiated thyroid cancer who have now been followed up to 18 yr. The presence of cancer was established by radioiodine scans, x-rays, and clinical examination. Thirty-two patients with detectable serum Tg autoantibodies were excluded from this analysis. Tg was measured by RIA with a sensitivity of 1 ng/mL. Patients who had all stages of cancer, but who had no evidence of active disease after treatment, were grouped according to operative and 131I ablative therapy. In patients with a partial thyroidectomy with or without ablation, the presence of Tg did not indicate the presence of cancer since levels were often above either a 5 ng/mL or a 10 ng/mL cutoff. The presence of residual normal thyroid tissue decreases the diagnostic value of serum Tg assay. In patients who underwent near total (NTT) or total thyroidectomy (TT) and 131I ablation, 3 of 55 (5.5%) patients had Tg greater than 5 ng/mL and 1 of 55 (1.8%) patients had Tg greater than 10 ng/mL during therapy, whereas off therapy 13 of 57 (22.8%) patients had Tg greater than 5 ng/mL and 6 of 57 (10.5%) patients had Tg levels greater than 10 ng/mL. In this group of patients, a Tg level less than 10 ng/mL during suppressive therapy indicated the absence of apparent tumor in 54 of 55 (98.2%) of patients. Whereas sensitivity of the assay was increased by withdrawal of hormone, "false positives" increased especially at lower (3-6 ng/mL) cut-off levels. No cut-off value properly categorized all patients. These data suggest, that even in patients who underwent 131I ablation and total thyroidectomy and were thought to be cured, small foci of thyroid tissue which are undetectable by standard 2 mCi 131I scans may exist and produce some Tg. However, these residual cells do not appear to cause an adverse prognosis in most patients. In patients with recurrent or continued disease, during T4 treatment, Tg levels ranged between 2-21,000 ng/mL and 5 of 11 patients had a Tg less than 5 ng/mL. Off treatment, Tg levels ranged between 6-10,700 ng/mL and 3 of 13 patients had a Tg less than 10 ng/mL. In 4 patients Tg levels were less than 10 ng/mL on treatment but greater than 10 ng/mL off therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Carcinoma diferenciado de tireóide: avaliação inicial e acompanhamento

“…Para Ozata, níveis de Tg menores que 3ng/ml raramente corresponderiam a recorrência tumoral (36). Estudos mais atuais apontam para níveis de 2,5ng/ml sem o uso do T4 (37).…”

Molecular technology and the recombinant TSH have changed diagnostics of thyroid carcinoma with positive I-131 whole body scan but low serum thyroglobulin

“…Patients who underwent near total thyroidectomy or total thyroidectomy followed by 131 I ablation can also show a progressive decrease of Tg as demonstrated by a 18 year follow-up study (Ozata et al, 1994). 131 I ablation and T4-suppressive therapy may play a role in determining gradual atrophy or death of residual cells able to produce Tg (Ozata et al, 1994). Therefore, the possibility of changes in biology and clinical appearance of disease has to be kept into account during long-term follow-up.…”

“…In presence of normal thyroid tissue, such as in patients with a partial thyroidectomy with or without ablation, the diagnostic value of Tg measure is obviously poor (Ozata et al, 1994). Different cut-off Tg values have been used in order to detect patients with active disease from those without known cancer.…”

The clinical utility of Lens culinaris agglutinin-reactive thyroglobulin ratio in serum for distinguishing benign from malignant conditions of the thyroid

“…At present, serum Tg is used for follow-up of thyroid carcinoma patients after treatment [9][10][11]. Traditionally, the follow-up of differentiated thyroid carcinoma consists of periodic withdrawal from L-T4-suppressive therapy to allow performance of a highly sensitive serum Tg measurement to detect recurrences.…”