(18)F-FDG PET/CT can be used to detect non-functioning pancreatic neuroendocrine tumors

Recent advances and future challenges in the diagnosis of neuroendocrine neoplasms

Neuroendocrine neoplasms (NEN) are a heterogeneous group of malignancies with increasing incidence, whose diagnosis is usually delayed, negatively impacting on patients' prognosis. The latest advances in pathological classifications, biomarker identification and imaging techniques may provide early detection, leading to personalized treatment strategies. In this narrative review the recent developments in diagnosis of NEN are discussed including progresses in pathological classifications, biomarker and imaging. Furthermore, the challenges that lie ahead are investigated. By discussing the limitations of current approaches and addressing potential roadblocks, we hope to guide future research directions in this field. This article is proposed as a valuable resource for clinicians and researchers involved in the management of NEN. Update of pathological classifications and the availability of standardized templates in pathology and radiology represent a substantially improvement in diagnosis and communication among clinicians. Additional immunohistochemistry markers may now enrich pathological classifications, as well as miRNA profiling. New and multi-analytical circulating biomarkers, as liquid biopsy and NETest, are being proposed for diagnosis but their validation and availability should be improved. Radiological imaging strives for precise, non-invasive and less harmful technique to improve safety and quality of life in NEN patient. Nuclear medicine may benefit of somatostatin receptors' antagonists and membrane receptor analogues. Diagnosis in NEN still represents a challenge due to their complex biology and variable presentation. Further advancements are necessary to obtain early and minimally invasive diagnosis to improve patients' outcomes.

The utility of 18F-FDG PET/CT in the diagnosis, staging of non-functioning pancreatic neuroendocrine tumors

Background

The non-functional PNETs are often discovered incidentally, they are commonly malignant and commonly present at a late stage with large size. We evaluate in this study the usefulness of 18F-FDG PET/CT in the detection and staging of non-functioning PNETs.

Results

Thirty patients with non-functioning PNETs were involved in this prospective study over a period starting from September 2016 to March 2021. Age ranged from 33 to 79 years. 18F-FDG PET/CT detected 26 patients had SUV max ≥ 2.5 of primary lesions and 4 lesions had SUV max < 2.5. There was no statistical significant between the site of the lesions and the type of grading of the tumors. 32 distant metastatic lesions were detected which show SUVmax ≥ 2.5 and only 9%where below 2.5. Of 30 patients, 4 patients (13.3%) of well differentiated tumor had altered their clinical strategies according to the results of PET/CT examinations. 18F-FDG PET/CT upstaged 1 patient with stage IB and 3 patients with IIA and B to stage IV.

Conclusion

The increased use of 18F-FDG PET/CT in the investigation of patient with PNETs allows for more accurate staging and therefore more appropriate management decision.

Recent Advances in Gene Therapy for Cancer Theranostics

There is great interest in developing gene therapies for many disease indications, including cancer. However, successful delivery of nucleic acids to tumor cells is a major challenge, and in vivo efficacy is difficult to predict. Cancer theranostics is an approach combining anti-tumor therapy with imaging or diagnostic capabilities, with the goal of monitoring successful delivery and efficacy of a therapeutic agent in a tumor. Successful theranostics must maintain a high degree of anticancer targeting and efficacy while incorporating high-contrast imaging agents that are nontoxic and compatible with clinical imaging modalities. This review highlights recent advancements in theranostic strategies, including imaging technologies and genetic engineering approaches. Graphical Abstract.

Role of PET/CT and Therapy Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show peculiar clinical and histomorphological features, with variable prognosis. In recent years, advances in knowledge regarding the pathophysiology and heterogeneous clinical presentation, as well as the availability of different diagnostic procedures for panNEN diagnosis and novel therapeutic options for patient clinical management, has led to the recognition of the need for an active multidisciplinary discussion for optimal patient care. Molecular imaging with positron emission tomography/computed tomography (PET/CT) has become indispensable for the management of panNENs. Several PET radiopharmaceuticals can be used to characterize either panNEN receptor expression or metabolism. The aim of this review is to offer an overview of all the currently used radiopharmaceuticals and of the new upcoming tracers for pancreatic neuroendocrine tumors (panNETs), and their clinical impact on therapy management. [68Ga]Ga-DOTA-peptide PET/CT (SSA-PET/CT) has high sensitivity, specificity, and accuracy and is recommended for the staging and restaging of any non-insulinoma well-differentiated panNEN cases to carry out detection of unknown primary tumor sites or early relapse and for evaluation of in vivo somatostatin receptors expression (SRE) to select patient candidates for peptide receptor radiometabolic treatment (PRRT) with 90Y or 177Lu and/or cold analogs. SSA-PET/CT also has a strong impact on clinical management, leading to a change in treatment in approximately a third of the cases. Its role for treatment response assessment is still under debate due to the lack of standardized criteria, even though some semiquantitative parameters seem to be able to predict response. [18F]FDG PET/CT generally shows low sensitivity in small growing and well-differentiated neuroendocrine tumors (NET; G1 and G2), while it is of utmost importance in the evaluation and management of high-grade NENs and also provides important prognostic information. When positive, [18F]FDG PET/CT impacts therapeutical management, indicating the need for a more aggressive treatment regime. Although FDG positivity does not exclude the patient from PRRT, several studies have demonstrated that it is certainly useful to predict response, even in this setting. The role of [18F]FDOPA for the study of panNET is limited by physiological uptake in the pancreas and is therefore not recommended. Moreover, it provides no information on SRE that has crucial clinical management relevance. Early acquisition of the abdomen and premedication with carbidopa may be useful to increase the accuracy, but further studies are needed to clarify its utility. GLP-1R agonists, such as exendin-4, are particularly useful for benign insulinoma detection, but their accuracy decreases in the case of malignant insulinomas. Being a whole-body imaging technique, exendin-PET/CT gives important preoperative information on tumor size and localization, which is fundamental for surgical planning as resection (enucleation of the lesion or partial pancreatic resection) is the only curative treatment. New upcoming tracers are under study, such as promising SSTR antagonists, which show a favorable biodistribution and higher tumor-to-background ratio that increases tumor detection, especially in the liver. [68Ga]pentixafor, an in vivo marker of CXCR4 expression associated with the behavior of more aggressive tumors, seems to only play a limited role in detecting well-differentiated NET since there is an inverse expression of SSTR2 and CXCR4 in G1 to G3 NETs with an elevation in CXCR4 and a decrease in SSTR2 expression with increasing grade. Other tracers, such as [68Ga]Ga-PSMA, [68Ga]Ga-DATA-TOC, [18F]SiTATE, and [18F]AlF-OC, are also under investigation.

Usefulness of 18 F-FDG-PET/CT in the diagnosis and prediction of recurrence of pancreatic neuroendocrine neoplasms

BACKGROUND

Although ¹⁸ F-FDG-PET/CT is a widely used diagnostic tool for several malignancies, its efficacy in diagnosing pancreatic neuroendocrine tumors is reported to be controversial because of the short-term follow-up.

METHODS

We retrospectively compared demographics and pathological features between ¹⁸ F-FDG-positive and -negative diseases. Additionally, we evaluated whether the avidity of ¹⁸ F-FDG-PET/CT affected earlier recurrence after curative treatment of non-functioning tumors. The median duration of observation was 65.6 months.

RESULTS

Seventy-two patients were enrolled. ¹⁸ F-FDG-positive diseases were pathologically advanced and significantly associated with metastatic behavior. In a multivariate analysis, metastatic behavior and WHO tumor grade was independently associated with ¹⁸ F-FDG accumulation. Only 25% of functional tumors (4/16) and 8% of insulinomas (1/12) were ¹⁸ F-FDG-positive. In a Kaplan-Meier analysis in patients with non-functioning tumors (n = 56), ¹⁸ F-FDG-positivity was significantly correlated with poorer recurrence-free survival (RFS) but had no correlation with overall survival. In univariate analysis of factors associated with shorter RFS, male gender, prevalence of nodal metastasis, WHO tumor grade ≥G2, or ¹⁸ F-FDG-positive disease were significantly higher in patients with shorter RFS, whereas only ¹⁸ F-FDG-positivity was associated with shorter RFS in multivariate analyses.

CONCLUSIONS

The avidity of ¹⁸ F-FDG-PET/CT was associated with metastatic behavior of pancreatic neuroendocrine tumors and recurrence after treatment of non-functioning tumors.

Novel PET tracers: added value for endocrine disorders

Nuclear medicine has been implicated in the diagnosis and treatment of endocrine disorders for several decades. With recent development of PET tracers, functional imaging now plays a major role in endocrine tumors enabling with high performance to their localization, characterization, and staging. Besides ¹⁸F-FDG, which may be used in the management and follow-up of endocrine tumors, new tracers have emerged, such as ¹⁸F-DOPA for neuroendocrine tumors (NETs) (medullary thyroid carcinoma, pheochromocytomas and paragangliomas and well-differentiated NETs originating from the midgut) and ¹⁸F-Choline in the field of primary hyperparathyroidism. Moreover, some peptides such as somatostatin analogs can also be used for peptide receptor radionuclide therapy. In this context, Gallium-68 labeled somatostatin analogs (⁶⁸Ga-SSA) can help to tailor therapeutic choices and follow the response to treatment in the so-called "theranostic" approach. This review emphasizes the usefulness of these three novel PET tracers (¹⁸F-Choline, ¹⁸F-FDOPA, and ⁶⁸Ga-SSA) for primary hyperparathyroidism and neuroendocrine tumors.

The utility of 68Ga-DOTATATE positron-emission tomography/computed tomography in the diagnosis, management, follow-up and prognosis of neuroendocrine tumors

Neuroendocrine tumors (NETs) are rare neoplasms that emerge mainly from the GI tract, pancreas and respiratory tract. The incidence of NETs has increased more than sixfold in the last decades. NETs typically express somatostatin receptors on their cell surface, which can be targeted by 'cold' somatostatin analogs for therapy or by 'hot' radiolabeled somatostatin analogs for tumor localization and treatment. 68-Gallium-DOTA peptides (DOTATATE, DOTATOC, DOTANOC) positron emission tomography/computed tomography is a highly accurate imaging modality for NETs that has been found to be more sensitive for NET detection than other imaging modalities. In the current review, we will discuss the clinical utility of 68-Gallium-DOTATATE positron emission tomography/computed tomography for the diagnosis and management of patients with NETs.

Carbohydrate antigen 19-9 as a prognostic biomarker in pancreatic neuroendocrine tumors

Carbohydrate antigen 19-9 (CA19-9) is not generally considered to be a biomarker in pancreatic neuroendocrine tumors (pNETs), as the majority of pNETs present with a normal range of CA19-9. The present study aimed to evaluate the role of serum CA19-9 levels as a prognostic factor in a relatively large number of patients with pNETs. Consecutive patients were retrospectively collected from a single institution between June 2006 and February 2015. The receiver operating characteristic (ROC) curve and the area under the ROC curve were used to select the cut-off values for the baseline CA19-9 levels. The primary end point was set as overall survival. Potential factors associated with the abnormal elevation of CA19-9 expression levels in pNETs were also investigated. The cut-off value for CA19-9 was 16 U/ml as determined by the ROC curve, and for the area under the ROC curve it was 0.68. In total, 32.7% of patients (51/156) had CA19-9 expression levels higher than the cut-off value. Univariate analysis demonstrated that CA19-9 >16 U/ml was an adverse prognostic factor for patients' overall survival. The CA19-9 >16 U/ml group had a statistically higher proportion of tumor node metastasis (TNM) stage III or IV, as compared with the CA19-9 ≤16 U/ml group. To the best of our knowledge, the present study is the first to demonstrate that CA19-9 is a prognostic biomarker of pNETs, one that may reflect its aggressiveness and severity.

Neutrophil-lymphocyte ratio predicts survival in pancreatic neuroendocrine tumors

Although the prognostic role of neutrophil-lymphocyte ratio (NLR) has been confirmed in a variety of tumors, the prognostic role of NLR in pancreatic neuroendocrine tumors (PNETs) has not been examined. The present study was performed to assess the role of NLR as a prognostic factor in patients with PNETs. Clinical data were retrospectively retrieved from a single institution. The best cut-off value for baseline NLR levels was determined by the receiver operating characteristic (ROC) curve and area under the ROC curve. The primary event was overall survival and event times were assessed by the Kaplan-Meier method. Potential factors associated with the elevation of NLR in PNETs were examined. A total of 165 consecutive patients with pathologically confirmed PNETs were included in this study. The cutoff value of NLR was 2.4 by ROC curve (area under ROC curve, 0.70). NLR >2.4 was found to be a poor prognostic factor in the univariate and multivariate analyses. Patients with a NLR value >2.4 had a higher proportion of tumor size at >3 cm (P=0.001), TNM stage III or IV (P=0.019), and G2/G3 (P=0.003). We concluded that NLR is an independent predictor of overall survival for patients with PNETs. Aberrant elevation of NLR identifies high-risk patients with aggressive characteristics.

A wait-and-watch approach to small pancreatic neuroendocrine tumors: prognosis and survival

Background

Whether all the small (ø≤20mm) non-functional pancreatic neuroendocrine neoplasms (pNENs) should be routinely resected is unclear.

Aim

To assess the overall survival (OS) and progression-free survival (PFS) of patients with small pNENs, followed-up with different management options.

Material and methods

Between 2007-2014, 51 patients were newly diagnosed with pNEN. 15 patients with pNENs ø ≤20 mm underwent an intensive follow-up at 3-month intervals during the first year and then every 6 months (FU pNEN group). They were all at TNM stage I, except for one patient at stage IIA. 21 patients underwent surgical resection (SR pNEN group): 2 patients were at TNM stage I, 9 IIA, one IIIB, 9 IV. 15 patients received systemic therapy (ST pNEN group) due to advanced disease or contraindications to surgery: 5 were at stage IIA, 2 IIB, 8 IV.

Results

The median follow-up for the entire cohort was 50 months. Survival was similar in the FU and SR pNEN groups, but significantly worst in the ST pNEN patients (log-rank test P <0.05). The 4-year survival rate was 100% in the FU pNEN group, 90.5% among the SR pNEN patients, 61% for the ST pNEN ones (p <0.0001). The disease remained stable in all but one patient in the FU pNEN group, whereas six patients in the SR group and five in the ST group showed disease progression.

Conclusions

The “wait-and-watch” approach to early-stage small pNENs appears to be safe although further studies are needed to confirm these results in larger cohorts of patients.

FBW7 (F-box and WD Repeat Domain-Containing 7) Negatively Regulates Glucose Metabolism by Targeting the c-Myc/TXNIP (Thioredoxin-Binding Protein) Axis in Pancreatic Cancer

PURPOSE

FBW7 functions as a tumor suppressor by targeting oncoproteins for destruction. We previously reported that the oncogenic mutation of KRAS inhibits the tumor suppressor FBW7 via the Ras-Raf-MEK-ERK pathway, which facilitates the proliferation and survival of pancreatic cancer cells. However, the underlying mechanism by which FBW7 suppresses pancreatic cancer remains unexplored. Here, we sought to elucidate the function of FBW7 in pancreatic cancer glucose metabolism and malignancy.

EXPERIMENTAL DESIGN

Combining maximum standardized uptake value (SUVmax), which was obtained preoperatively via a PET/CT scan, with immunohistochemistry staining, we analyzed the correlation between SUVmax and FBW7 expression in pancreatic cancer tissues. The impact of FBW7 on glucose metabolism was further validated in vitro and in vivo Finally, gene expression profiling was performed to identify core signaling pathways.

RESULTS

The expression level of FBW7 was negatively associated with SUVmax in pancreatic cancer patients. FBW7 significantly suppressed glucose metabolism in pancreatic cancer cells in vitro Using a xenograft model, MicroPET/CT imaging results indicated that FBW7 substantially decreased 18F-fluorodeoxyglucose ((18)F-FDG) uptake in xenograft tumors. Gene expression profiling data revealed that TXNIP, a negative regulator of metabolic transformation, was a downstream target of FBW7. Mechanistically, we demonstrated that TXNIP was a c-Myc target gene and that FBW7 regulated TXNIP expression in a c-Myc-dependent manner.

CONCLUSIONS

Our results thus reveal that FBW7 serves as a negative regulator of glucose metabolism through regulation of the c-Myc/TXNIP axis in pancreatic cancer. Clin Cancer Res; 22(15); 3950-60. ©2016 AACR.

The clinical utility of CA125/MUC16 in pancreatic cancer: A consensus of diagnostic, prognostic and predictive updates by the Chinese Study Group for Pancreatic Cancer (CSPAC)

The prognosis for pancreatic cancer (PC) is poor; however, the timely and accurate treatment of this disease will significantly improve prognosis. Serum biomarkers involve non-invasive tests that facilitate the early detection of tumors, predict outcomes and assess responses to therapy, so that the patient can be continuously monitored and receive the most appropriate therapy. Studies have reported that cancer antigen (CA)125 [also known as mucin 16 (MUC16)] has functional significance in the tumorigenic, metastatic and drug resistant properties of PC. Our aim was to use this biomarker in the diagnosis, detection of metastasis, prognosis and in the monitoring of the treatment effects of PC. Members of the Chinese Study Group for Pancreatic Cancer (CSPAC) reviewed the literature on CA125/MUC16 and developed an objective consensus on the clinical utility of CA125/MUC16 for PC. They confirmed the role of CA125/MUC16 in tumorigenesis and the progression of PC, and recommended monitoring CA125/MUC16 levels in all aspects of the diagnosis and treatment of PC, particularly those that involve the monitoring of treatments. In addition, they suggested that the combination of other biomarkers and imaging techniques, together with CA125/MUC16, would improve the accuracy of the clinical decision-making process, thereby facilitating the optimization of treatment strategies. Periodic clinical updates of the use of CA125/MUC16 have been established, which are important for further analyses and comparisons of clinical results from affiliates and countries, particularly as regards the in-depth biological function and clinical translational research of this biomarker.

A comprehensive comparison of clinicopathologic and imaging features of incidental/symptomatic non-functioning pancreatic neuroendocrine tumors: A retrospective study of a single center

BACKGROUND

Incidentally discovered, nonfunctioning pancreatic endocrine tumors (NF-pNETs) are being increasingly diagnosed with the widespread use of imaging examination. The objective of this study was to analyze the different clinicopathologic and imaging features between incidentally discovered and symptomatic NF-pNETs.

METHODS

From March 2010 to October 2014, we retrospectively analyzed 102 patients with pathologically confirmed sporadic NF-pNETs, among which 49 (48.0%) had lesions that were discovered incidentally. Differences in clinicopathologic features and various computerized tomography (CT) and endoscopic ultrasonography (EUS) findings were evaluated between incidental and symptomatic NF-pNETs.

RESULTS

Among 102 patients with NF-pNETs, 49 (48.0%) had lesions that were discovered incidentally. Incidental NF-pNETs were more highly associated with low tumor grades, stages and lymphatic metastasis compared with symptomatic tumors (p = 0.007, 0.029 and 0.003, respectively). Moreover, incidental NF-pNETs had a lower rate of hypoenhancement (p = 0.018), main pancreatic duct dilatation (p = 0.043), and unclear border (p = 0.022). In addition, hypoechoic lesion was the most common and had a slightly higher rate in symptomatic tumors (p = 0.032).

CONCLUSIONS

Incidental NF-pNETs are associated with lower rates of aggressive behaviors of clinicopathologic and imaging features compared with symptomatic tumors.