Somatostatin receptor scintigraphy in the follow-up of patients with differentiated thyroid cancer

The aim of this study was to compare the results of somatostatin receptor s cintigraphy (SRS) and of radioiodine scintigraphy in patients with metastat ic differentiated thyroid carcinoma during L-thyroxine suppression therapy and after withdrawal. Twenty-five patients were studied: 16 patients had pa pillary cancer and 12 of them had metastatic disease; 9 patients had follic ular cancer and 7 of these had known metastases. In 7 patients SRS was perf ormed during thyroxine withdrawal, in 12 during thyroxine therapy within 9 months from radioiodine scintigraphy, in 6 others both during suppression t herapy and after withdrawal. SRS was positive in 18 of 25 (72%) patients. I t demonstrated lesions in 11 of 13 (85%) patients after thyroxine withdrawa l and in 12 of 18 (67%) patients during thyroxine suppression. In 6 patient s in whom a direct comparison was made before and after withdrawal, essenti ally the same information was obtained. Six of 8 (75%) patients with lesion s that did not concentrate radioiodine showed uptake of labeled octreotide in these lesions. In 5 of 17 (29%) patients whose tumors concentrated radio iodine, no uptake was found during SRS. Conclusions: 1) in patients with me tastatic differentiated thyroid carcinoma, tumor sites can be visualized us ing SRS; 2) there is no need to withdraw patients from suppression therapy in order to perform SRS; 3) in some patients whose lesions do concentrate l abeled octreotide but not radioiodine, the use of somatostatin analogues la beled with In-111 or [Y-90] can provide new therapeutic options. (J. Endocr inol. Invest. 24: 415-422, 2001) (C) 2001, Editrice Kurtis.