Is super(68)Ga-DOTA-NOC PET/CT indicated in patients with clinical, biochemical or radiological suspicion of neuroendocrine tumour?

Purpose: In recent years, super(68)Ga-DOTA-peptides positron emission tomography (PET)/CT has been increasingly used to study patients with neuroendocrine tumours (NET). However, performing specialized examinations in the appropriate contest is mandatory for both medical and economic reasons. The aim of the study is to evaluate the potential usefulness of super(68)Ga-DOTA-NOC PET/CT in patients with suspected NET. Methods: Among the patients undergoing super(68)Ga-DOTA-NOC PET/CT at our centre, we reviewed those studied for suspected NET based on the presence of either clinical signs/symptoms or imaging or raised biochemical markers or a combination of these conditions. PET/CT results were compared with clinical and imaging follow-up of at least 1 year or pathology. Results: Overall 131 suspected NET cases were included. The most common condition considered suspicious for NET was the increase of blood markers (66), followed by inconclusive findings at conventional imaging (CI, 41), clinical signs/symptoms (10), equivocal super(18)F-fluorodeoxyglucose (FDG) PET (7) or somatostatin receptor scintigraphy (SRS, 4), or a combination of the above (3). PET/CT results were true-positive in 17 cases, true-negative in 112 and false-negative in 2 (overall sensitivity 89.5 %, specificity 100 %). Interestingly, increased blood markers and clinical signs/symptoms were associated with the lowest frequency of true-positive findings (1/66 and 1/10, respectively), while CI findings were confirmed in one third of the cases (13/41). Overall, the incidence of NET in the studied population was 14.5 % (19/131). Conclusion: Our data confirm the good accuracy (98 %) of super(68)Ga-DOTA-NOC PET/CT in NET lesion detection. However, our results also suggest that super(68)Ga-DOTA-NOC PET/CT may not be routinely recommended in patients with a suspicion of NET based on the mere detection of increased blood markers or clinical symptoms. Positive CI alone or in association with clinical/biochemical findings is on the contrary associated with a higher probability of true-positive findings.