Long-term follow-up using serial serum thyroglobulin determinations in patients with differentiated thyroid carcinoma

Abstract

Although thyroglobulin is generally recognized as a useful marker for metastases in cases of differentiated thyroid carcinoma, there have been few reports of the use of thyroglobulin determination for long‐term follow‐up. This report presents the results of long‐term follow‐up studies carried out for periods of up to 4 years in 18 patients, including 4 patients with local and 14 with distant metastases. After successful treatment, thyroglobulin fell to unmeasurable levels in the four patients with local metastases and in four of six patients with distant metastases. In some patients treated successfully with 131I, the thyroglobulin level remained elevated for several months before falling to within the normal range. Thyroglobulin levels correlated with tumor growth in six of eight patients with tumor progression, remained high with a slight downward trend in one patient, and declined to unmeasurable levels in another case. Only one patient in this group showed radioiodine uptake in the metastases at the end of the observation period. The lack of 131I uptake in the other patients probably reflects the low degree of differentiation of the metastases. The following conclusions regarding the use of thyroglobulin measurement for the long‐term follow‐up of thyroid carcinoma can be made: (1) Following 131I therapy for metastatic thyroid carcinoma, return of thyroglobulin levels to within the normal range may take several months. The trend observed in serial thyroglobulin determinations is more meaningful than the absolute values for evaluating the success of therapy. (2) Thyroglobulin levels correlate with tumor growth in most cases of tumor progression, even when changes in differentiation may have led to a loss of radioiodine uptake by the metastases. It may be concluded that serial thyroglobulin determinations are therefore useful for the detection of metastases that do not accumulate radioiodine.

Circulating thyroglobulin measurements by homologous radioimmunoassay in dogs with thyroid carcinoma

“…Plasma Tg levels decreased after thyroidectomy (Fig. 2), similarly to observations in human thyroid cancer (36). Although the level returned to normal in 7 of the 8 dogs (88%), none had undetectable levels, in contrast to humans with thyroid cancer.…”

Tumor Markers and Oncogene Expression in Thyroid Cancer using Biochemical and Immunohistochemical Studies.

“…However, increased concentrations of Tg have also been seen in many thyroidal diseases, other than differentiated thyroid carcinoma (Botsch et al, 1983;Madeddu et al, 1985). RIA of Tg has often been jeopadized by the presence of and-thyroglobulin antibody in the patient's serum.…”

How to deal with undetectable and low measurable serum thyroglobulin levels in the follow-up of patients with differentiated thyroid carcinoma?

“…In earlier studies serum Tg levels have been below the 'critical values' used in 1.5% of the cases with detectable iodine accumulating tissue suggestive of the presence of residual, recurrent or metastatic cancer (Charles 1982). Serum Tg may also reveal the presence of resi¬ dual or recurrent thyroid cancer tissue which does not accumulate radioiodine and is in such a situa¬ tion superior to the whole body scanning (Charles et al 1980;Pacini et al 1980;Schneider et al 1981;Charles 1982;Echenique et al 1982;Galligan et al 1982;Botsch et al 1983;Hüfner et al 1983;Ericsson et al 1984). On the other hand, it is clear that the use of such a low critical value to some extent increases the need for control examinations some of which will be of limited use in the sense that the results do not influence the management of the patient.…”