Somatostatin receptor scintigraphy in medullary thyroid carcinoma

Background111In-radiolabelled (DTPA-D-Phe1)-octreotide scintigraphy can be used to localize neuroendocrine tumours expressing somatostatin receptors (SSTRs). The aim of this paper was to analyse the importance of tumour volume and growth for the visualization by SSTR scintigraphy of metastases from medullary thyroid carcinoma (MTC). Methods Serum calcitonin concentrations were used to estimate volume and growth rate of MTC. Twenty-two patients who had persistent hypercalcitoninaemia after total thyroidectomy for MTC, indicating the presence of metastases, were studied. Results SSTR scintigraphy visualized 15 tumours in 11 patients. Patients with scintigraphically visualized tumours had higher serum calcitonin and carcinoembryonic antigen concentrations and larger tumours, and the serum calcitonin concentration increased more rapidly with time. Tumour-associated symptoms and death from MTC occurred only in patients with scintigraphically visualized tumours. Conclusion Scintigraphically visualized tumours grow more rapidly and are more aggressive than non-visualized lesions. SSTR scintigraphy can be helpful in the planning of palliative surgery for MTC and for diagnosing distant metastases, but cannot localize microscopic metastases.