Interlesional Heterogeneity of Metastatic Neuroendocrine Tumors Based on 18F-DOPA PET/CT

Purpose Neuroendocrine tumors (NETs) can produce neuroendocrine amines resulting in symptoms. Selecting the most active amine-producing tumor lesions for local treatment might be beneficial for patients with metastatic small intestinal NET. Tumor burden correlates with catecholamine pathway activity. We analyzed interlesional heterogeneity with 18F-DOPA PET scans in patients with small intestinal NET and investigated if lesions with substantially higher 18F-DOPA uptake could be identified. Methods In this retrospective, observational study, the 18F-DOPA uptake was calculated by dividing SUVpeak of the lesion by the SUVmean of the background organ. The magnitude of heterogeneity between lesions within a patient was calculated by dividing the lesion with the highest by the one with the lowest 18F-DOPA uptake. Lesions with a higher 18F-DOPA uptake than the upper inner or outer fence (>1.5 or 3 times the interquartile range above the third quartile) were defined as lesions with mild or extreme high 18F-DOPA uptake, respectively, and presence of these was determined in patients with 10 lesions or more. Results 18F-DOPA was detected over 680 lesions in 38 patients, of which 35 were serotonin producing. 18F-DOPA uptake varied with a median of 8-fold up to 44-fold between lesions within a patient. In 12 of 20 evaluable patients, lesions with mild high 18F-DOPA uptake were found, and in 5, lesions with extreme high 18F-DOPA uptake. Conclusions 18F-DOPA-PET showed considerable heterogeneity in 18F-DOPA uptake between tumor lesions and identified lesions within patients with mild or extreme high 18F-DOPA uptake.