Clinical implications of somatostatin-receptor scintigraphy in ophthalmic Graves' disease

The role of the scintigraphy using 111In-DTPA-d-Phe1-octreotide as well as of treatment with somatostatin analogues in TAO is still under debate. Patients with very active eye disease are likely to respond favourably to immunosuppression: in these patients, the activity of ophthalmopathy is clinically evident and further assessment with 111In-DTPA-d-Phe1-octreotide scintigraphy could be considered unnecessary. In many patients with moderately severe ophthalmopathy, however, it is not clear whether or not eye disease is still in the active stage and, thus, whether or not the patient will benefit from immunosuppression. In these cases, orbital scintigraphy using 111In-DTPA-d-Phe1-octreotide might be used as a predictor for the outcome of immunosuppressive treatments. However, prediction using the technique of orbital SRS requires great accuracy, so each institution should develop its own cut-off values. Scintigraphy is an expensive method with a not-inconsiderable radiation burden. The future availability of somatostatin analogues labelled with 99mtechnetium could overcome such problems. Moreover, orbital scintigraphy with 111In-DTPA-d-Phe1-octreotide is not specific, since positive scans may be obtained in patients with orbital meningioma, malignant lymphoma, pseudo-tumour orbitae, orbital myositis, sarcoidosis, Wegener's granulomatosis, necrotizing scleritis, sinusitis or infections of the nasal mucosa. Finally, orbital scintigraphy does not allow precise imagingand thus the evaluation of eye-muscle swelling and apical crowding still requires imaging with CT or MRI scans (Fig. 4). Similarly, treatment of Graves' ophthalmopathy with somatostatin analogues needs further validation from controlled studies before it can be considered as an alternative to the standard immunosuppressive treatment with steroids and irradiation.