INDIUM-111-PENTETREOTIDE IN GRAVES-DISEASE

Thyroidal and orbital lymphocytic infiltration in Graves' disease, as well as identification of somatostatin receptors on lymphocytes, has p rovided a rationale for receptor imaging with the radiolabeled somatos tatin analog pentetreotide. Recently, we demonstrated that in contrast to controls, Graves' patients showed markedly increased orbital accum ulation of pentetreotide. Longitudinal and follow-up data are presente d here. Methods: In 20 (16 hyperthyroid) Graves' patients with active eye disease, planar (thyroid) and SPECT (orbit) images were performed 4 and 24 hr after injection of In-111-pentetreotide (222 MBq) before a nd 3 mo after starting antithyroid and combined steroid and orbital ra diotherapy. Results: Thyroidal uptake decreased during methimazole tre atment (4 hr postinjection, median: hyperthyroid 989 counts/pixel/MBq injected activity, euthyroid 253 counts, p = 0.001; 24 hr, 437 versus 95 counts/pixel/MBq, p = 0.005). Fourteen patients (70%) responded to steroid and radiotherapy. The pentetreotide orbit-to-brain ratio decre ased markedly after completion of therapy (4 hr: 25 before versus 6.2 after therapy, p = 0.0003; 24 hr: 9.6 versus 2.7, p = 0.003). A high p retreatment ratio correlated with a response to therapy (p = 0.001: in 14 of 16 patients with a ratio > 10, 4 hr postinjection, ophthalmopat hy improved; positive predictive value: 90%; median activity score bef ore 6 versus 2 after therapy, p = 0.0001) in contrast to none of the f our cases with a ratio less than 10 (score 5 versus 4, p = 0.08), Conc lusion: Pentetreotide scans may be regarded as a semiobjective tool in the evaluation of Graves' disease, both at initial stages as well as during treatment.