Somatostatin receptor scintigraphy of orbital inflammatory pseudotumor associated with systemic vasculitis

Abstract

Objective To explore the value of somatostatin receptor scintigraphy(SRS) in evaluating the immune activity of orbital inflammatory pseudotumor associated with systemic vasculitis. Methods Twenty-five patients with orbital inflammatory pseudotumor associated with systemic vasculitis (10 males, 15 females, average age: (51.2±14.2) years) underwent SRS. The uptake ratio (UR) of orbital inflammatory pseudotumor was obtained. (1)Patients were divided into group A (with immune activity) and group B (without immune activity) according to Birmingham vasculitis activity score (BVAS). The difference of UR between the 2 groups was compared by two-sample t test. The difference of UR before and after treatment in 12 patients was also compared. (2) Based on the results by BVAS, ROC curve was used to obtain the cut-off value of UR, as well as the diagnostic efficiency and Youden index. The consistency between SRS and BVAS was calculated. (3)Patients were divided into two groups according to the cut-off value of UR and the prognosis difference between them was compared by Fisher exact test. (4)The expression of SSTR2 and SSTR5 was observed by immunohistochemistry. Results (1)UR in group A was significantly higher than that in group B (2.09±0.44 vs 1.32±0.46, t=5.94, P 0.05). (2)ROC curve analysis identified UR cut-off value as 1.66, with the sensitivity of 87.5%, specificity of 95.7%, positive predictive value of 95.2%, negative predictive value of 88.0%, accuracy of 91.3% and Youden index of 83.2%. The consistency between SRS and BVAS was strong (Kappa=0.840). (3) The prognosis was significantly different between patients with UR≥1.66 and UR<1.66 (P<0.05). (4) The immunohistochemical results revealed high expression of SSTR2 and SSTR5 in inflammatory cells in patients with immune activity. Conclusion SRS has potential value in evaluating the immune activity of orbital inflammatory pseudotumor associated with systemic vasculitis. Key words: Orbital pseudotumor; Systemic vasculitis; Radionuclide imaging; Receptors, somatostatin