Imaging of pancreatic neuroendocrine tumors: recent advances, current status, and controversies

Abstract

Recently, there have been a number of advances in imaging pancreatic neuroendocrine tumors (panNETs), as well as other neuroendocrine tumors (NETs), which have had a profound effect on the management and treatment of these patients, but in some cases are also associated with controversies. Areas covered: These advances are the result of numerous studies attempting to better define the roles of both cross-sectional imaging, endoscopic ultrasound, with or without fine-needle aspiration, and molecular imaging in both sporadic and inherited panNET syndromes; the increased attempt to develop imaging parameters that correlate with tumor classification or have prognostic value; the rapidly increasing use of molecular imaging in these tumors and the attempt to develop imaging parameters that correlate with treatment/outcome results. Each of these areas and the associated controversies are reviewed. Expert commentary: There have been numerous advances in all aspects of the imaging of panNETs, as well as other NETs, in the last few years. The advances are leading to expanded roles of imaging in the management of these patients and the results being seen in panNETs/GI-NETs with these newer techniques are already being used in more common tumors.

(Radio)Theranostic Patient Management in Oncology Exemplified by Neuroendocrine Neoplasms, Prostate Cancer, and Breast Cancer

“…The (semi)-quantitative assessment of the response, using [ 68 Ga]Ga-SST PET/CT, to the endoradiotherapy with 177 Lu-or 90 Y-based somatostatin analogues and re-staging of the disease have entered clinical practice. Patient selection, prognosis, prediction of absorbed dose for radiotherapy, and treatment response based on [ 68 Ga]Ga-SST PET/CT have been performed using various parameters such as maximum standardized uptake value (SUV max ), tumor-to-background SUV max ratio (TBR), tumor-to-liver SUV max ratio (TLR), tumor-to spleen SUV max ratio (TSR), functional volume (FV), K-Patlak and Ki [60,76,[82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97]. SUV max cut-off of 16.4 was proposed for patient stratification for endoradiotherapy [84].…”

Prevention and Management of Hormonal Crisis during Theragnosis with LU-DOTA-TATE in Neuroendocrine Tumors. A Systematic Review and Approach Proposal

“…Positron emission tomography (PET) uses positron-emitting radioisotopes (18F, 11C, 68Ga), a new generation of tracers whose shorter half-life reduces patients’ radiation. In addition, PET offers a higher spatial resolution, detects more lesions, and allows a quantification of their uptake (standard uptake value, SUV) of great utility in therapy monitoring [ 9 ]. These are the studies currently considered of whenever they are available, since they change the follow-up strategy in more than 70% of patients [ 10 ].…”

Unmet Needs in Functional and Nonfunctional Pancreatic Neuroendocrine Neoplasms

“…This recommendation is based on the findings that NF-PanNENs of this size are not associated with increased mortality in MEN1 patients, many do not grow or show aggressive behavior, and these patients cannot be completely cured of PanNENs, because they all have small, microscopic NF-PanNEN tumors throughout the gland and only 0–12% ever become symptomatic [5, 11, 12, 45-47]. Only recently is this approach being increasingly used in patients with sporadic, asymptomatic NF-PanNENs [19-21, 23, 48]. This recommendation is not without controversy, with some authors advocating surgery for all PanNENs, whereas others support the conclusion that small, asymptomatic PanNENs are good candidates for surveillance [19-21, 49-52].…”

“…The prognostic pathologic features included here are discussed in more detail in proposed protocol 2, below. Recent studies report that a number of radiologic parameters can have predictive value for tumor aggressiveness and correlate to varying degrees with the pathologic grading [48]. These include the correlation of grading/tumor aggressiveness with 18 F- fluorodeoxyglucose (FDG) PET/CT positivity, the 18 F-FDG maximum standardized uptake (SUV/MAX) value, as well as the diffusion-weighted MRI apparent diffusion coefficient values [48, 54-57].…”

“…Recent studies report that a number of radiologic parameters can have predictive value for tumor aggressiveness and correlate to varying degrees with the pathologic grading [48]. These include the correlation of grading/tumor aggressiveness with 18 F- fluorodeoxyglucose (FDG) PET/CT positivity, the 18 F-FDG maximum standardized uptake (SUV/MAX) value, as well as the diffusion-weighted MRI apparent diffusion coefficient values [48, 54-57]. Recent studies report that the Ki-67 value correlates significantly with the size of the PanNEN [58, 59], thus this should be studied prospectively in more detail.…”