Physiological uptake of 68Ga-DOTATATE in the pancreas: Does it matter?

Objectives The objective of this study was to assess the relevance of physiological 68Ga-DOTATATE PET/CT findings in the pancreas guided by morphological imaging (MI) in relation to pathological tumor uptake in patient with neuroendocrine tumors (NET).

Methods 138 pts with pancreatic NET (pNET;n=38) or non-pNET (n=100) underwent 68Ga-DOTATATE PET/CT (2010-2013).Pancreatic regions with intensity higher than background were localized with the aid of anatomical reference (HUP:head/uncinate process; BT:body/tail) and classified as tumor (intense uptake and CT finding),suspicious (focal uptake and no CT finding) or physiological (faint uptake and no CT finding);SUVmax and mean were assessed. PET/CT findings were compared with MI.

Results Physiological uptake with no abnormal MI findings were seen in 10/38 pNETs (SUVmax, range, mean ± SD, and median in HUP and BT were 2.4-12.7, 5.9±3.2, 4.6 and 3.8-6.6, 6.6±2.5, 5.6, respectively). In contrast, 18/28 scans from pts with suspected pNET were considered pathologic (6.9-50, 26.9±13.5, 27 and 10-151, 32.2±36, 19.4, respectively). Notably,10/28 pts in the latter group had discordant PET/CT versus MI data: 2 pts had negative PET/CT (4mm and 12 mm lesions were seen on CT); 6 HUP suspicious uptake did not correspond to abnormal findings on MI; 6 BD suspicious uptake on PET/CT corresponded to calcification (1/6), cystic lesions (2/6) or negative findings (3/6) on MI. Finally uptake variables among 100 pts in the non-pNET group were: 2.1-17.9, 6.7±2.5, 6.4 and 3.33-28, 6.7±3.1, 6.5, respectively. In 3 of these pts, suspicious pancreatic uptake was detected (SUVmax, range, mean ± SD: 4.4-12.3; 8.9± 4) without concordant findings on MI.

Conclusions We report detectable 68Ga-DOTATATE physiological uptake in pancreas but of lower SUVmax than tumors. Equivocal findings had SUVmax between physiological and pathological ranges, and for these lesions MI and histological confirmation are required for final diagnosis.We conclude that low diffuse uptake of 68Ga-DOTATATE within the pancreas requires confirmation.