Staging and Functional Characterization of Pheochromocytoma and Paraganglioma by 18F-Fluorodeoxyglucose (18F-FDG) Positron Emission Tomography

Abstract

Pheochromocytomas and paragangliomas (PPGLs) are rare tumors of the adrenal medulla and extra-adrenal sympathetic chromaffin tissues; their anatomical and functional imaging are critical to guiding treatment decisions. This study aimed to compare the sensitivity and specificity of ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (¹⁸F-FDG PET/CT) for tumor localization and staging of PPGLs with that of conventional imaging by [¹²³I]-metaiodobenzylguanidine single photon emission CT (¹²³I-MIBG SPECT), CT, and magnetic resonance imaging (MRI). A total of 216 patients (106 men, 110 women, aged 45.2 ± 14.9 years) with suspected PPGL underwent CT or MRI, ¹⁸F-FDG PET/CT, and ¹²³I-MIBG SPECT/CT. Sensitivity and specificity were measured as endpoints and compared by the McNemar test, using two-sided P values only. Sixty (28%) of patients had nonmetastatic PPGL, 95 (44%) had metastatic PPGL, and 61 (28%) were PPGL negative. For nonmetastatic tumors, the sensitivity of ¹⁸F-FDG was similar to that of ¹²³I-MIBG but less than that of CT/MRI (sensitivity of ¹⁸F-FDG = 76.8%; of ¹²³I-MIBG = 75.0%; of CT/MRI = 95.7%; ¹⁸F-FDG vs ¹²³I-MIBG: difference = 1.8%, 95% confidence interval [CI] = −14.8% to 14.8%, P = .210; ¹⁸F-FDG vs CT/MRI: difference = 18.9%, 95% CI = 9.4% to 28.3%, P < .001). The specificity was 90.2% for ¹⁸F-FDG, 91.8% for ¹²³I-MIBG, and 90.2% for CT/MRI. ¹⁸F-FDG uptake was higher in succinate dehydrogenase complex– and von Hippel–Lindau syndrome–related tumors than in multiple endocrine neoplasia type 2 (MEN2) related tumors. For metastases, sensitivity was greater for ¹⁸F-FDG and CT/MRI than for ¹²³I-MIBG (sensitivity of ¹⁸F-FDG = 82.5%; of ¹²³I-MIBG = 50.0%; of CT/MRI = 74.4%; ¹⁸F-FDG vs ¹²³I-MIBG: difference = 32.5%, 95% CI = 22.3% to 42.5%, P < .001; CT/MRI vs ¹²³I-MIBG: difference = 24.4%, 95% CI = 11.3% to 31.6%, P < .001). For bone metastases, ¹⁸F-FDG was more sensitive than CT/MRI (sensitivity of ¹⁸F-FDG = 93.7%; of CT/MRI = 76.7%; difference = 17.0%, 95% CI = 4.9% to 28.5%, P = .013). Compared with ¹²³I-MIBG SPECT and CT/MRI, both considered gold standards for PPGL imaging, metastases were better detected by ¹⁸F-FDG PET. ¹⁸F-FDG PET provides a high specificity in patients with a biochemically established diagnosis of PPGL.