Hydroxyephedrine in Tumors of the Sympathetic Nervous System: Feasibility Study and Comparison with 123I-MIBG SPECT/CT

The 11C-labeled tracer meta-hydroxyephedrine (11C-HED) is a noradrenaline analog that was developed to visualize the sympathetic nervous system with PET. Initial clinical studies show a rapid uptake of 11C-HED in localized tumors of this system. Whole-body imaging with 11C-HED PET is now possible as PET/CT scanners allow a rather short examination time. The aim of this study was to evaluate the feasibility of whole-body 11C-HED PET/CT for examination of tumors of the sympathetic nervous system and to directly compare the results with 123Ilabeled meta-iodobenzylguanidine (123I-MIBG) scintigraphy, including SPECT/CT. Methods: In 19 consecutive patients, 9 mo to 68 y old (median, 32 y), 24 whole-body 11C-HED PET/CT (low-dose CT) examinations were performed. Scans were compared with attenuation-corrected 123I-MIBG SPECT/CT scans (24-h scan, low-dose CT). The intensity of tracer accumulation above background was visually analyzed in both scans, PET and SPECT, using a 4-value scale. In 11C-HED PET, mean and maximum standardized uptake values were determined for all lesions. Results: In 14 patients with 19 pairs of examinations, the following tumors were confirmed histologically: 6 neuroblastomas, 5 pheochromocytomas, 1 ganglioneuroblastoma, and 2 paragangliomas. In 5 patients, each having 1 pair of examinations, clinical follow-up and/or histologic examination did not reveal any tumor deriving from the sympathetic nervous system. 11C-HED PET/CT detected 80 of 81 totally depicted tumor lesions (sensitivity, 0.99; soft tissue, 61; bone, 19). 123I-MIBG SPECT/CT detected 75 of 81 lesions (sensitivity, 0.93; soft tissue, 56; bone, 19).With bothmethods, therewere no false-positive lesions. The tumor-to-background contrast of 11C-HED uptake was higher in comparison with 123I-MIBG uptake in 26 lesions (0.32; soft tissue, 18; bone, 8), equal in 39 lesions (0.48; soft tissue, 30; bone, 9), and lower than 123I-MIBG uptake in 16 lesions (0.20; soft tissue, 14; bone, 2).Conclusion:Whole-body imaging using 11C-HED PET/CT is feasible in the clinical setting of patients with tumors of the sympathetic nervous system. 11C-HED PET/CT detected more tumor lesions than 123I-MIBG SPECT/CT. However, tumor-to-background contrast of 11CHED in lesions can be higher, equal, or lower compared with 123I-MIBG.