title: Current knowledge on the sensitivity of the (68)Ga-somatostatin receptor positron emission tomography and the SUVmax reference range for management of pancreatic neuroendocrine tumours.
abstract: Physiologically increased pancreatic uptake at the head/uncinate process is observed in more than one-third of patients after injection of one of the three (68)Ga-labelled octreotide-based peptides used for somatostatin (sst) receptor (r) imaging. There are minor differences between these (68)Ga-sstr-binding peptides in the imaging setting. On (68)Ga-sstr-imaging the physiological uptake can be diffuse or focal and usually remains stable over time. Differences in the maximal standardised uptake values (SUVmax) reported for the normal pancreas as well as for pancreatic neuroendocrine tumour (PNET) lesions may be related to several factors, including (a) differences in the peptide binding affinities as well as differences in sstr subtype expression of pancreatic α- and β-cells, and heterogeneity / density of tumour cells, (b) differences in scanner resolution, image reconstruction techniques and acquisition protocols, (c) mostly retrospective study designs, (d) mixed patient populations, or (e) interference with medications such as treatment with long-acting sst analogues. The major limitation in most of the studies lies in the lack of histopathological confirmation of abnormal findings. There is a significant overlap between the calculated SUVmax-values for physiological pancreas and PNET-lesions of the head/uncinate process that do not favour the use of quantitative parameters in the clinical setting. Anecdotal long-term follow-up studies have even indicated that increased uptake in the head/uncinate process still can turn out to be malignant over years of follow up. SUVmax-data for the pancreatic body and tail are limited. Therefore, any visible focal tracer uptake in the pancreas must be considered as suspicious for malignancy irrespective of quantitative parameters. In general, sstr-PET/CT has significant implications for the management of NET patients leading to a change in treatment decision in about one-third of patients. Therefore, follow-up with (68)Ga-sstr-PET/CT is mandatory in the clinical setting if uptake in the head/uncinate process is observed.
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. irene.virgolini@i-med.ac.at.
authors.forename: Irene
authors.initials: I
authors.lastname: Virgolini
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Gabriel
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kroiss
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: von Guggenberg
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Rupert
authors.initials: R
authors.lastname: Prommegger
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Boris
authors.initials: B
authors.lastname: Warwitz
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Nilica
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Llanos Geraldo
authors.initials: LG
authors.lastname: Roig
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Margarida
authors.initials: M
authors.lastname: Rodrigues
authors.affiliation: Department of Nuclear Medicine, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Uprimny
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D019317:Evidence-Based Medicine; D005710:Gallium Radioisotopes / Q000493:pharmacokinetics*; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D057054:Molecular Imaging / Q000379:methods; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000601:surgery; D015282:Octreotide / Q000493:pharmacokinetics; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000601:surgery; D049268:Positron-Emission Tomography / Q000592:standards*; D017410:Practice Guidelines as Topic; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D005710:Gallium Radioisotopes; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D015282:Octreotide
keywords: 68Ga-somatostatin analogue; Neuroendocrine tumour; Pancreatic imaging; SUVmax-calculation; Sensitivity; Specificity; Uncinate process