Octreotide-scintigraphy is a disease-activity parameter in Graves' ophthalmopathy

OBJECTIVE It is thought that immunosuppressive treatment of Graves' ophthal mopathy should be restricted to patients with active eye disease, but asses sing disease activity is difficult. Octreotide scintigraphy has been claime d to differentiate active from inactive disease. Here we study the intraobs erver variability and diagnostic accuracy of the quantitative measurement o f orbital octreotide uptake. PATIENTS AND DESIGN Twenty-two consecutive patients with moderately severe ophthalmopathy were treated with retrobulbar radiotherapy. Pretreatment oct reotide scintigraphic data were related to the response at six months after radiotherapy, using Receiving-Operator-Characteristic curves. MEASUREMENTS Octreotide uptake was measured at 4 and 24 h after i.v. inject ion of approximately 3 mCi (=111 MBq; range 75-150 MBq) (111)Indium-DTPA-Oc treotide with a neuro-SPECT camera. Counts were measured in fixed regions-o f-interest in 4 transversal slices of the orbit, the temporal and the occip ital area. Measurements were done twice and intraobserver variability was a nalysed by coefficients of variations (CV), Uptake is expressed as orbital/ background ratio. The nature of the temporal uptake was studied by matching an octreoscan with a technetium scan and MRI. RESULTS Intra-observer variability of measuring octreotide uptake was accep table, and the coefficient of variation slightly better using the orbital/o ccipital ratio (11%), than the orbital/temporal ratio (16%). From matching studies it appears that the temporal uptake takes place, in part, in the pa rotid gland. The orbital/occipital ratio was used to predict the outcome of radiotherapy. Mean (+/-SD) uptake on the 4 h scan was higher in responders (2.2 +/- 0.66) than in nonresponders (1.7 +/- 0.39; P = 0.04). From the Re ceiving-Operator-Characteristic curve we determined a cut-off value of 1.85 , which yielded a positive predictive value of 92% and a negative predictiv e value of 70%. The 24 h scan could not predict a response. CONCLUSION Quantitative measurement of orbital octreotide uptake is possibl e. Using the orbital/occipital ratio on the 4 h scan, the octreoscan seems useful in predicting response to subsequent radiotherapy. The 24 h scan see ms not to be useful in predicting therapeutic outcome.