Molecular Imaging of Gastroenteropancreatic Neuroendocrine Tumors: Current Status and Future Directions

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to (1) summarize the main clinical features of gastroenteropancreatic neuroendocrine tumors; (2) describe the specific mechanisms of uptake of radiotracers and identify the relation of imaging phenotype with site of origin and tumor grade; and (3) recommend the best imaging modalities across the different tumor subtypes for imaging and for selecting candidates for peptide receptor radionuclide therapy.

Prospective evaluation of 68Ga‐DOTATATE PET/CT in limited disease neuroendocrine tumours and/or elevated serum neuroendocrine biomarkers

“…Sensitivities were calculated for patients and for involved anatomical regions. The differences in sensitivity between the imaging procedures were compared using the chi test and Fisher's exact test when n was <5, according to Hawass et al…”

“…These tumours may be diagnostically challenging since primary or secondary lesions can be millimetric in size. Furthemore, it is known that anatomic imaging can fail to locate these extremely small tumours, especially those located in the midgut . The role of imaging is to provide the most comprehensive and precise evaluation at initial staging and re‐staging of NETs.…”

“…Novel PET radiotracers like 18 F‐fluorodopa ( 18 F‐FDOPA) and 68 Ga‐labelled somatostatin analogues ( 68 Ga‐DOTA‐SSAs) appear promising. 18 F‐FDOPA PET/CT performed better than SRS and CT of midgut NETs but may have suboptimal sensitivity in some pancreatic NETs . Several studies have shown that 68 Ga‐DOTA‐SSAs like 68 Ga‐DOTATATE, 68 Ga‐DOTATOC and 68 Ga‐DOTANOC have a high detection rate and a high impact on patient management, especially in NETs with unknown primary or in potential candidates for curative surgery or requiring liver transplantation.…”

Association between neuroendocrine tumors biomarkers and primary tumor site and disease type based on total 68Ga-DOTATATE-Avid tumor volume measurements

“…111 In-pentetreotide (Octreoscan) has been widely used for NET imaging, but is limited by its low image resolution and long scan duration and relatively lower SSTRs affinity[8]. In contrast, the 68 -Gallium ( 68 Ga)-DOTA-compounds recently introduced into clinical practice ( 68 Ga-DOTATATE, 68 Ga-DOTANOC, 68 Ga-DOTATOC), have been shown to have higher sensitivity for detecting NET than Octreoscan[9] and significantly impact the management of patients with NET [10,11]. …”

Pancreatic neuroendocrine tumors

“…SRS provides for scanning of the whole body and allows detection of metastases outside of the abdominal region. Furthermore, SRS can offer functional information based on the levels of somatostatin receptor expression and contributes to selection of appropriate candidates for somatostatin-based therapies (33). However, SRS is limited by the expression of somatostatin receptors.…”