Frequency and significance of physiological versus pathological uptake of 68Ga-DOTATATE in the pancreas: Validation with morphological imaging

AIM: The objective of this study was to assess the relevance of physiological Ga-DOTATATE PET/CT findings in the pancreas guided by morphological imaging (MI) in comparison with pathological tumour uptake in patients with neuroendocrine tumours (NETs). METHODS: A total of 138 patients with pancreatic NET (pNET; n=38) or non-pNET (n=100) underwent Ga-DOTATATE PET/CT. Pancreatic regions with intensity higher than background were localized with anatomical reference support [head/uncinate process (HUP); body/tail (BT)] and classified as tumour, suspicious or physiological. Maximum standardized uptake value (SUVmax) was assessed in all regions. PET/CT findings were compared with MI results. RESULTS: Physiological uptake was seen in 10/38 pNETs (SUVmax range, mean±SD and median in HUP and BT: 2.4-12.7, 5.9±3.2 and 4.6; 3.8-6.6, 6.6±2.5 and 5.6, respectively). A total of 18/38 showed high uptake (SUVmax range, mean±SD and median in HUP and BT: 6.9-50, 26.9±13.5 and 27; 10-151, 32.2±36 and 19.4, respectively) with abnormal MI results. Among 10/38 patients we observed a total of n=15 discordant findings between PET/CT and MI: two lesions detected by MI did not correspond to any pathologial uptake on PET/CT, five suspicious uptake in the HUP did not correspond to any abnormal finding on MI, one HUP suspicious uptake correspondend to a lymphadenopaty on MI and seven suspicious BT uptake correspondend to calcification (1/6), cystic lesions (3/6), lesion different form the one detected by PET/CT (1/6) or negative findings (2/6) on MI. Among the 100 patients with non-pNETs, 97 showed homogeneous uptake and three had suspicious pancreatic uptake without concordant findings on MI. CONCLUSION: Physiological pancreatic uptake of Ga-DOTATATE showed low SUVmax, whereas tumours showed higher SUVmax; this is in agreement with previously published data. Equivocal findings showed SUVmax in the grey area between physiological and pathological ranges, and for these lesions MI and histological confirmation are required for final diagnosis.