Ga-DOTATOC PET/CT in the localization of head and neck paraganglioma compared with F-DOPA PET/CT and I-MIBG SPECT/CT.

PURPOSE

F-Fluoro-L-dihydroxyphenylalanine (F-DOPA) PET offers high sensitivity and specificity in the imaging of non-malignant head and neck paraganglioma (HNPGL) but lower sensitivity in metastatic disease of these neuroendocrine tumours (NET). In contrast to the radiotracer F-DOPA, both I-meta-iodo-benzylguanidine (I-MIBG) and Ga-DOTA-Tyr3-octreotide (Ga-DOTA-TOC) offer valuable clinical information on norepinephrine and somatostatin (SST) receptor status for planning I-MIBG and radionuclide peptide therapy (PRRT), respectively. Therefore, we compared Ga-DOTA-TOC and F-DOPA PET/CT with I-MIBG planar and SPECT/CT imaging, for the detection of HNPGL. Combined cross-sectional imaging was the reference standard.

METHODS

A total of 3 men and 7 women (age range 22 to 73 years) with anatomical and/or histologically proven HNPGL were included in this study. Of these patients, 3 patients had metastatic HNPGL. Comparative evaluation included morphological imaging with CT and functional imaging with Ga-DOTA-TOC and F-DOPA PET, including I-MIBG imaging. The imaging results were analysed on a per-patient and per-lesion basis.

RESULTS

On a per-patient analysis, the detection rate of both Ga-DOTA-TOC PET/CT and F-DOPA PET/CT was 100%, that of planar I-MIBG imaging 10.0% and that of SPECT/CT 20.0%. On a per-lesion basis and in reference to diagnostic CT, the sensitivity of Ga-DOTA-TOC PET/CT was 100% (McNemar, P < 0.5), that of F-DOPA PET/CT was 66.7% (McNemar, P < 0.01), that of planar I-MIBG imaging was 3.7% (McNemar, P < 0.0001), and that of SPECT/CT was 7.4% (McNemar, P < 0.0001) in HNPGL. Overall, Ga-DOTA-TOC PET identified 29 lesions and anatomical imaging identified 27 lesions. F-DOPA PET identified 18 lesions, whereas planar I-MIBG imaging identified 1 lesion and SPECT/CT 2 lesions.

CONCLUSION

Ga-DOTA-TOC PET/CT is superior for imaging, non-malignant and metastatic HNPGL compared to F-DOPA PET/CT and planar I-MIBG imaging, including SPECT/CT, particularly in bone lesions. Combined functional/anatomical imaging (Ga-DOTA-TOC PET/CT) enables excellent delineation of tumour extent in these rare tumour entities. Compared to I-MIBG scintigraphy, Ga-DOTA-TOC PET appears far more useful for planning radionuclide therapy in patients with surgically inoperable tumours or metastatic disease.