Usefulness of Tl-201 chloride scintigraphy in detection of metastasis and radioiodine therapy for metastasis of differentiated thyroid carcinoma

The aim of this study was to compare Tl-201 scintigraphy with I-131 scintigraphy and to assess whether T1-201 scintigraphy has diagnostic advantages in detecting metastasis of patients with thyroid carcinoma. All patients had undergone total thyroidectomy or subthyroidectomy. The study population included 4 men and 11 women, with ages ranging from 11-69 years. Eight had follicular adenocarcinomas, and 7 had papillary adenocarcinomas (including mixed papillary-follicular). The positive detection rate of both Tl-201 and I-131 scintigraphy was 67%, which correlated with the histological type (75% of papillary type and 63% of follicular type). Tl-201 scintigraphy has the advantage of detecting non-functioning metastases. On the other hand, I-131 scintigraphy has the advantage of detecting occult functioning metastases.Factors affecting the effect of radioiodine treatment for metastasis of 15 patients with differentiated thyroid cancer were studied. We evaluated the effect of I-131 treatment by the degree of I-131 accumulation shown on the scintigram. The degree of I-131 uptake in metastases was related to age, histology and type of metastatic lesion. Good I-131 uptake in metastases was found in patients less than 40 years old, with papillary adenocarcinoma and without bone metastasis.