Comparación entre la PET/TC con ¹⁸ F-DOPA y la PET/TC con ⁶⁸ Ga-DOTATOC para la localización del paraganglioma maligno extra-adrenal y el feocromocitoma

Objective: ¹⁸ F-Fluoro-L-dihydroxyphenylalanine ( ¹⁸ F-DOPA) PET offers high sensitivity and specificity in the imaging of non-malignant extra-adrenal paraganglioma (PGL) and pheochromocytoma (PHEO) but lower sensitivity in metastatic disease. These tumours are of neuroendocrine origin and can be detected by ⁶⁸ Ga-DOTA-Tyr3-octreotide ( ⁶⁸ Ga-DOTA-TOC) PET. Therefore, we compared ⁶⁸ Ga-DOTA-TOC and ¹⁸ F-DOPA as radiolabels for PET/CT imaging for the diagnosis of metastatic extra-adrenal PGL and PHEO. Combined cross-sectional imaging was the reference standard. Methods: A total of 6 men and 4 women (age range 22–72 years) with anatomical and/or histologically proven metastatic PGL and PHEO were included in this study. Of these patients, 2 male patients suffered from PHEO, while the remaining 8 patients were diagnosed as metastatic extra-adrenal PGL disease. Comparative evaluation included morphological imaging with CT and functional imaging with ⁶⁸ Ga-DOTA-TOC and ¹⁸ F-DOPA PET. The imaging results were analyzed on a per-lesion basis. The maximum standardized uptake value (SUV _max ) of each functional imaging modality in concordant tumour lesions was measured. Results: Compared with anatomical imaging, the per-lesion detection rate of ⁶⁸ Ga-DOTA-TOC was 100% (McNemar, P < 0.01), and that of ¹⁸ F-DOPA PET was 82.3% (McNemar, P < 0.8) in metastatic extra-adrenal PGL and PHEO. Overall, ⁶⁸ Ga-DOTA-TOC PET identified 67 lesions; anatomical imaging identified 62 lesions, and ¹⁸ F-DOPA PET identified 56 lesions. The SUV _max (mean ± SD) of all concordant lesions was 29.3 ± 19.9 for ⁶⁸ Ga-DOTA-TOC PET and 12.3 ± 9.1 for ¹⁸ F-DOPA PET (Mann–Whitney U test, P < 0.0001). Conclusion: ⁶⁸ Ga-DOTA-TOC PET offers the highest detection rate in metastatic extra-adrenal PGL and PHEO compared to ¹⁸ F-DOPA PET and even to diagnostic CT, particularly in bone lesions. Combined functional/anatomical imaging ( ⁶⁸ Ga-DOTA-TOC PET/CT) enables exact tumour extension to be detected in these rare tumour entities, especially in the case of unclear anatomical correlation.