Pancreatic neuroendocrine tumours: hypoenhancement on arterial phase computed tomography predicts biological aggressiveness

Neuroendocrine Tumors: Diagnostics

Neuroendocrine neoplasms (NEN) are rare tumors arising from neuroendocrine cells. NEN are ideally suited for a theragnostic approach due to their specific expression of somatostatin receptors (SSTR). SSTR imaging of NEN dates back to the 1980s, but has evolved recently due to the introduction of more sensitive SSTR PET radiotracers. SSTR PET is a primary imaging modality for identifying NEN and characterizing SSTR expression. SSTR PET is complementary to anatomic imaging for assessing tumor response to treatment. SSTR PET is mandated to determine eligibility for peptide receptor radionuclide therapy. Here, the role of imaging to aid management of NEN is reviewed.

Imaging differentiation of solid pseudopapillary neoplasms and neuroendocrine neoplasms of the pancreas

Purpose

The present study aimed to compare the computed tomography (CT) and magnetic resonance imaging (MRI) features of solid pseudopapillary neoplasms (SPNs) and pancreatic neuroendocrine neoplasms (pNENs).

Method

Lesion imaging features of 39 patients with SPNs and 127 patients with pNENs were retrospectively extracted from 104 CT and 91 MRI scans.

Results

Compared to pNEN patients, SPN patients were significantly younger (mean age 51.8 yrs versus 32.7 yrs) and more often female (female: male ratio, 5.50:1 versus 1.19:1). Most SPNs and pNENs presented as well-defined lesions with an expansive growth pattern. SPNs more often appeared as round or ovoid lesions, compared to pNENs which showed a lobulated or irregular shape in more than half of cases (p<0.01). A surrounding capsule was detected in the majority of SPNs, but only in a minority of pNENs (<0.01). Hemorrhage occurred non-significantly more often in SPNs (p=0.09). Signal inhomogeneity in T1-fat-saturated (p<0.01) and T2-weighted imaging (p=0.046) as well as cystic degeneration (p<0.01) were more often observed in SPNs. Hyperenhancement in the arterial and portal-venous phase was more common in pNENs (p<0.01). Enlargement of locoregional lymph nodes (p<0.01) and liver metastases (p=0.03) were observed in some pNEN patients, but not in SPN patients. Multivariate logistic regression identified the presence of a capsule (p<0.01), absence of arterial hyperenhancement (p<0.01), and low patient age (p<0.01), as independent predictors for SPN.

Conclusions

The present study provides three key features for differentiating SPNs from pNENs extracted from a large patient cohort: presence of a capsule, absence of arterial hyperenhancement, and low patient age.

Accuracy and Prognostic Impact of Nodal Status on Preoperative Imaging for Management of Pancreatic Neuroendocrine Tumors: A Multi-Institutional Study

BACKGROUND

We sought to define the accuracy of preoperative imaging to detect lymph node metastasis (LNM) among patients with pancreatic neuroendocrine tumors (pNETs), as well as characterize the impact of preoperative imaging nodal status on survival.

METHODS

Patients who underwent curative-intent resection for pNETs between 2000 and 2020 were identified from eight centers. Sensitivity and specificity of computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET)-CT, and OctreoScan for LNM were evaluated. The impact of preoperative lymph node status on lymphadenectomy (LND), as well as overall and recurrence-free survival was defined.

RESULTS

Among 852 patients, 235 (27.6%) individuals had LNM on final histologic examination (hN1). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 12.4%, 98.1%, 71.8%, and 74.4% for CT, 6.3%, 100%, 100%, and 80.1% for MRI, 9.5%, 100%, 100%, and 58.7% for PET, 11.3%, 97.5%, 66.7%, and 70.8% for OctreoScan, respectively. Among patients with any combination of these imaging modalities, overall sensitivity, specificity, PPV, and NPV was 14.9%, 97.9%, 72.9%, and 75.1%, respectively. Preoperative N1 on imaging (iN1) was associated with a higher number of LND (iN1 13 vs. iN0 9, p = 0.003) and a higher frequency of final hN1 versus preoperative iN0 (iN1 72.9% vs. iN0 24.9%, p < 0.001). Preoperative iN1 was associated with a higher risk of recurrence versus preoperative iN0 (median recurrence-free survival, iN1→hN1 47.5 vs. iN0→hN1 92.7 months, p = 0.05).

CONCLUSIONS

Only 4% of patients with LNM on final pathologic examine had preoperative imaging that was suspicious for LNM. Traditional imaging modalities had low sensitivity to determine nodal status among patients with pNETs.

Prognostic value of CT-based radiomics in grade 1-2 pancreatic neuroendocrine tumors

BACKGROUND

Surgically resected grade 1-2 (G1-2) pancreatic neuroendocrine tumors (PanNETs) exhibit diverse clinical outcomes, highlighting the need for reliable prognostic biomarkers. Our study aimed to develop and validate CT-based radiomics model for predicting postsurgical outcome in patients with G1-2 PanNETs, and to compare its performance with the current clinical staging system.

METHODS

This multicenter retrospective study included patients who underwent dynamic CT and subsequent curative resection for G1-2 PanNETs. A radiomics-based model (R-score) for predicting recurrence-free survival (RFS) was developed from a development set (441 patients from one institution) using least absolute shrinkage and selection operator-Cox regression analysis. A clinical model (C-model) consisting of age and tumor stage according to the 8th American Joint Committee on Cancer staging system was built, and an integrative model combining the C-model and the R-score (CR-model) was developed using multivariable Cox regression analysis. Using an external test set (159 patients from another institution), the models' performance for predicting RFS and overall survival (OS) was evaluated using Harrell's C-index. The incremental value of adding the R-score to the C-model was evaluated using net reclassification improvement (NRI) and integrated discrimination improvement (IDI).

RESULTS

The median follow-up periods were 68.3 and 59.7 months in the development and test sets, respectively. In the development set, 58 patients (13.2%) experienced recurrence and 35 (7.9%) died. In the test set, tumors recurred in 14 patients (8.8%) and 12 (7.5%) died. In the test set, the R-score had a C-index of 0.716 for RFS and 0.674 for OS. Compared with the C-model, the CR-model showed higher C-index (RFS, 0.734 vs. 0.662, p = 0.012; OS, 0.781 vs. 0.675, p = 0.043). CR-model also showed improved classification (NRI, 0.330, p < 0.001) and discrimination (IDI, 0.071, p < 0.001) for prediction of 3-year RFS.

CONCLUSIONS

Our CR-model outperformed the current clinical staging system in prediction of the prognosis for G1-2 PanNETs and added incremental value for predicting postoperative recurrence. The CR-model enables precise identification of high-risk patients, guiding personalized treatment planning to improve outcomes in surgically resected grade 1-2 PanNETs.

Tumor vascularity on contrast-enhanced computed tomography as a predictive marker of metastatic potential for small nonfunctioning pancreatic neuroendocrine tumors

BACKGROUND

Although surgical resection is generally suggested for nonfunctioning pancreatic neuroendocrine tumors, observation can be proposed for carefully selected patients with small tumors. However, the indications for observation remain unclear.

METHODS

This retrospective study included 77 patients with nonfunctioning pancreatic neuroendocrine tumors, including small tumors (≤2.0 cm, n = 41), who received pancreatectomy. The ratio of the mean computed tomography value of a tumor in the late arterial/equilibrium phase (computed tomography a/e ratio) was used to evaluate tumor vascularity. Pathologic examinations of small tumors were conducted. The associations among the computed tomography a/e ratio, pathologic findings, and survival outcomes were investigated.

RESULTS

Small tumors were pathologically categorized by the degree of fibrosis as follows: medullary (n = 20), intermediate (n = 11), and fibrotic (n = 10). The fibrotic type had significantly lower computed tomography a/e ratios than the medullary type (median, 1.42 vs 2.03, P < .001). The median number of vessels with microscopic venous invasion was significantly higher in the fibrotic type than in the medullary type (4.5 vs 0.0, P < .001). The cutoff value of the computed tomography a/e ratio for predicting microscopic venous invasion was determined to be 1.54 by the receiver operating characteristic curve (area under the curve, 0.832; sensitivity, 80.0%; specificity, 83.9%; accuracy, 82.9%). Microscopic venous invasion was an independent prognostic factor for relapse-free survival in overall patients (hazard ratio 5.18, P = .017).

CONCLUSION

The computed tomography a/e ratio may be a useful predictor of the metastatic potential of nonfunctioning pancreatic neuroendocrine tumors and may help decide the indications of observation for small nonfunctioning pancreatic neuroendocrine tumors.

Maximum Value on Arterial Phase Computed Tomography Predicts Prognosis and Treatment Efficacy of Sunitinib for Pancreatic Neuroendocrine Tumours

PURPOSE

This study was designed to assess the computed tomography maximum (CTmax) value on pretherapeutic arterial phase computed tomography (APCT) images to predict pancreatic neuroendocrine tumours (pNETs) recurrence and clarify its role in predicting the outcome of tumour therapy.

METHODS

This retrospective study enrolled 250 surgical patients and 24 nonsurgical patients with sunitinib-based treatment in our hospital from 2008 to 2019. CT images were assessed, the maximum value was defined as "CTmax," and recurrence-free survival (RFS) or progression-free survival (PFS) was compared between a high-CTmax group and a low-CTmax group among patients who underwent surgical resection or nonsurgical, sunitinib-based treatment according to the CTmax cutoff value.

RESULTS

In ROC curve analysis, a CTmax of 108 Hounsfield units, as the cutoff value, achieved an AUC of 0.796 in predicting recurrence. Compared with the low-CTmax group, the high-CTmax group had a longer RFS (p < 0.001). Low CTmax was identified as an independent factor for RFS (p < 0.001) in multivariate analysis; these results were confirmed using the internal validation set. The CTmax value was significantly correlated with the microvascular density (MVD) value (p < 0.001) and the vascular endothelial growth factor receptor 2 (VEGFR2) score (p < 0.001). Furthermore, the high-CTmax group had a better PFS than the low-CTmax group among the sunitinib treatment group (p = 0.007).

CONCLUSIONS

The tumour CTmax on APCT might be a potential and independent indicator for predicting recurrence in patients who have undergone surgical resection and assessing the efficacy of sunitinib for patients with advanced metastatic pNETs.

Aberrant transcription factors in the cancers of the pancreas

Transcription factors (TFs) are essential for proper activation of gene set during the process of organogenesis, differentiation, lineage specificity. Reactivation or dysregulation of TFs regulatory networks could lead to deformation of organs, diseases including various malignancies. Currently, understanding the mechanism of oncogenesis became necessity for the development of targeted therapeutic strategy for different cancer types. It is evident that many TFs go awry in cancers of the pancreas such as pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine neoplasms (PanNENs). These mutated or dysregulated TFs abnormally controls various signaling pathways in PDAC and PanNENs including RTK, PI3K-PTEN-AKT-mTOR, JNK, TGF-β/SMAD, WNT/β-catenin, SHH, NOTCH and VEGF which in turn regulate different hallmarks of cancer. Aberrant regulation of such pathways have been linked to the initiation, progression, metastasis, and resistance in pancreatic cancer. As of today, a number of TFs has been identified as crucial regulators of pancreatic cancer and a handful of them shown to have potential as therapeutic targets in pre-clinical and clinical settings. In this review, we have summarized the current knowledge on the role and therapeutic usefulness of TFs in PDAC and PanNENs.

Advances in the imaging of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms comprise a heterogeneous group of tumors that differ in their pathogenesis, hormonal syndromes produced, biological behavior and consequently, in their requirement for and/or response to specific chemotherapeutic agents and molecular targeted therapies. Various imaging techniques are available for functional and morphological evaluation of these neoplasms and the selection of investigations performed in each patient should be customized to the clinical question. Also, with the increased availability of cross sectional imaging, these neoplasms are increasingly being detected incidentally in routine radiology practice. This article is a review of the various imaging modalities currently used in the evaluation of neuroendocrine neoplasms, along with a discussion of the role of advanced imaging techniques and a glimpse into the newer imaging horizons, mostly in the research stage.

Prediction of recurrence after surgery based on preoperative MRI features in patients with pancreatic neuroendocrine tumors

OBJECTIVES

To investigate useful MRI features in pancreatic neuroendocrine tumor (PNET) patients for predicting recurrence and its timing after surgery.

METHODS

A total of 99 patients with PNET who underwent MRI and surgery from 2000 to 2018 were enrolled. Two radiologists independently assessed MRI findings, including size, location, margin, T1 and T2 signal intensity, enhancement patterns, common bile duct (CBD) or main pancreatic duct (MPD) dilatation, vascular invasion, lymph node enlargement, DWI, and ADC value. Imaging findings associated with recurrence and disease-free survival (DFS) were assessed using logistic regression analysis and Cox proportional hazard regression analysis.

RESULTS

The median follow-up period was 40.4 months, and recurrence after surgery occurred in 12.1% (12/99). Among them, 6 patients experienced recurrence within 1 year, and 9 patients experienced recurrence within 2 years after surgery. In multivariate analysis, major venous invasion (OR 10.76 [1.14-101.85], p = 0.04) was associated with recurrence within 1 year, and portal phase iso- to hypoenhancement (OR 51.89 [1.73-1557.89], p = 0.02), CBD or MPD dilatation (OR 10.49 [1.35-81.64], p = 0.03) and larger size (OR 1.05 [1.00-1.10], p = 0.046) were associated with recurrence within 2 years. The mean DFS was 116.4 ± 18.5 months, and the 5-year DFS rate was 85.7%. In multivariate analysis, portal phase iso- to hypoenhancement (HR 21.36 [2.01-197.77], p = 0.01), ductal dilatation (HR 5.22 [1.46-18.68], p = 0.01), major arterial invasion (HR 42.90 [3.66-502.48], p = 0.003), and larger size (HR 1.04 [1.01-1.06], p = 0.01) showed a significant effect on poor DFS.

CONCLUSION

MRI features, including size, enhancement pattern, vascular invasion, and ductal dilatation, are useful in predicting recurrence and poor DFS after surgery in PNET. Key Points • MRI features are useful for predicting prognosis in patients with PNET after surgery. • PV or SMV invasion (OR 10.49 [1.35-81.64], p = 0.04) was significantly associated with 1-year recurrence. • Portal phase iso- to hypoenhancement (HR 21.36), CBD or MPD dilatation (HR 5.22), arterial invasion (HR 42.90), and larger size (HR 1.04) had significant effects on poor DFS (p < 0.05).

Somatostatin Receptor Imaging and Theranostics: Current Practice and Future Prospects

A new era of precision diagnostics and therapy for patients with neuroendocrine neoplasms began with the approval of somatostatin receptor (SSTR) radiopharmaceuticals for PET imaging followed by peptide receptor radionuclide therapy (PRRT). With the transition from SSTR-based γ-scintigraphy to PET, the higher sensitivity of the latter raised questions regarding the direct application of the planar scintigraphy-based Krenning score for PRRT eligibility. Also, to date, the role of SSTR PET in response assessment and predicting outcome remains under evaluation. In this comprehensive review article, we discuss the current role of SSTR PET in all aspects of neuroendocrine neoplasms, including its relation to conventional imaging, selection of patients for PRRT, and the current understanding of SSTR PET-based response assessment. We also provide a standardized reporting template for SSTR PET with a brief discussion.

Differentiation between non-hypervascular pancreatic neuroendocrine tumors and mass-forming pancreatitis using contrast-enhanced computed tomography

BACKGROUND

Non-hypervascular pancreatic neuroendocrine tumors (PNETs) showed slight or iso-enhancement in contrast-enhanced computed tomography (CE-CT), which shared similar imaging findings with mass-forming pancreatitis (MFPs).

PURPOSE

To explore the value of CT imaging features in differentiating the two diseases.

MATERIAL AND METHODS

Fifty-one patients with histologically proved MFPs (n = 27) or non-hypervascular PNETs (n = 24) were included. Two radiologists reviewed CT imaging findings and clinical features. Logistic regression analysis was performed to identify relevant features in differentiating non-hypervascular PNETs and MFPs. Receiver operating characteristic (ROC) curve analysis was used to show the performance of the optimal parameters in differentiating non-hypervascular PNETs and MFPs.

RESULTS

A well-defined margin was more common in non-hypervascular PNETs (P < 0.05) than that in MFPs. MFPs often occurred in older people (P < 0.01) and the head-neck of the pancreas compared with non-hypervascular PNETs (P < 0.05). Metastases only presented in non-hypervascular PNETs (P < 0.05). CT values at venous phase and delay phase of MFPs were higher (P = 0.010 and P = 0.029) than those in non-hypervascular PNETs. Logistic analysis showed gender, tumor margin, CT values at venous phase, and tumor components were independent predictors in differentiating the two lesions. The area under the curve (AUC) was 0.938 with a sensitivity of 87.5% and specificity of 92.6% for combined predicators.

CONCLUSION

Gender, tumor margin, CT values at venous phase, and tumor components were useful predicators in differentiating non-hypervascular PNETs and MFPs.

Presentation and outcome of mixed neuroendocrine non-neuroendocrine neoplasms of the pancreas

BACKGROUND/OBJECTIVES

Mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) of the pancreas and periampullary region are extremely rare and heterogeneous malignancies. Literature is sparse, clinical management is not standardized and little is known about survival outcomes. The aim of this study was to identify pathological and radiological features of MiNEN and assess the outcome of surgical management.

METHODS

Patients undergoing surgery for pancreatic and periampullary MiNEN between 2001 and 2019 were retrospectively analysed based on a prospective database. Histological, radiological and clinical features were assessed. Survival was analysed in a nested case-control study and matched-pair analyses with pure neuroendocrine neoplasms (pNEN) and ductal adeno- or acinar cell carcinomas of the pancreas. A literature review with focus on survival after surgical resection was additionally performed.

RESULTS

Of 13 patients with MiNEN, 5 had acinar-MiNEN and 8 adeno-MiNEN. Two of 5 (40%) acinar-MiNEN and one adeno-MiNEN patients had liver metastases. All but one adeno-MiNEN (88%) showed preoperative radiological features of pancreatic adenocarcinoma, 3 of 5 (60%) acinar-MiNEN exhibited mainly neuroendocrine features. No surgical mortality was observed. The 5-year overall survival rate in all MiNEN was 40%. Five-year survival rate was 58% in adeno-MiNEN and comparable to that of matched ductal adenocarcinomas (36%) and pNEN (48%). Five-year overall survival rate was 20% in acinar-MiNEN, compared to 39% in acinar carcinoma patients and 59% in matched pNEN patients.

CONCLUSIONS

MiNEN are rare and difficult to distinguish from pure adenocarcinoma or neuroendocrine neoplasm preoperatively. Surgical resection would therefore be the treatment of choice in localized tumors.

Dynamic Enhancement Pattern on CT for Predicting Pancreatic Neuroendocrine Neoplasms with Low PAX6 Expression: A Retrospective Observational Study

Paired box 6 (PAX6) is a transcription factor that plays a critical role in tumor suppression, implying that the downregulation of PAX6 promotes tumor growth and invasiveness. This study aimed to examine dynamic computed tomography (CT) features for predicting pancreatic neuroendocrine neoplasms (Pan-NENs) with low PAX6 expression. We retrospectively evaluated 51 patients with Pan-NENs without synchronous liver metastasis to assess the pathological expression of PAX6. Two radiologists analyzed preoperative dynamic CT images to determine morphological features and enhancement patterns. We compared the CT findings between low and high PAX6 expression groups. Pathological analysis identified 11 and 40 patients with low and high PAX6 expression, respectively. Iso- or hypoenhancement types in the arterial and portal phases were significantly associated with low PAX6 expression (p = 0.009; p = 0.001, respectively). Low PAX6 Pan-NENs showed a lower portal enhancement ratio than high PAX6 Pan-NENs (p = 0.044). The combination based on enhancement types (iso- or hypoenhancement during arterial and portal phases) and portal enhancement ratio (≤1.22) had 54.5% sensitivity, 92.5% specificity, and 84.3% accuracy in identifying low PAX6 Pan-NENs. Dynamic CT features, including iso- or hypoenhancement types in the arterial and portal phases and lower portal enhancement ratio may help predict Pan-NENs with low PAX6 expression.

Pancreatic neuroendocrine tumors (pNETs): the predictive value of MDCT characteristics in the differentiation of histopathological grades

PURPOSE

To investigate the correlation between multiple detector computed tomography (MDCT) features of pancreatic neuroendocrine tumors (pNETs) and histopathologic grade and find valuable imaging criteria for grade prediction.

MATERIAL AND METHODS

MDCT of 61 patients with 65 masses, which pNETs were approved histopathologically, underwent revision retrospectively. Each MDCT was evaluated for various radiologic characteristics. Absolute and relative (R: tumor/pancreas, D: tumor-pancreas) tumor enhancements were calculated in multiple post contrast phases.

RESULTS

61 patients [mean age = 50.70 ± 14.28 y/o and 30(49.2%) were male] were evaluated and classified into 2 groups histopathologically: G₁: 32 (49.2%) and G_2,3: 33 (50.8%). Significant relationships were observed between histopathologic tumor grade regarding age (p = 0.006), the longest tumor size (p = 0.006), presence of heterogeneity (p < 0.0001), hypodense foci in delayed phase (p = 0.004), lobulation (p = 0.002), vascular encasement (p < 0.0001), adjacent organ invasion (p = 0.01), presence (p < 0.0001) and number (0.02) of liver metastases, presence of lymphadenopathy with short axis of more than 10 mm (LAP) (p = 0.008), pathologic lymph node size (p = 0.004), relative (R and D) (p = 0.05 and 0.02, respectively), and percentage of arterial hyper-enhancing area (p = <0.0001). Tumor grades, however, had no significant relationship with gender, tumor location, tumor outline, calcification, cystic change, or pancreatic (PD) or biliary duct (BD) dilation (p = 0.21, 0.60, 0.05, 0.05 1, 0.10, and 0.51, respectively). Then, we suggested a novel imaging criteria consisting of six parameters (tumor size > 33 mm, relative (R) tumor enhancement in arterial phase ≤ 1.33, relative (D) tumor enhancement in arterial phase ≤ 16.5, percentage of arterial hyper-enhancing area ≤ 75%, vascular encasement, and lobulation), which specificity and accuracy of combination of all findings (6/6) for predicting G_2,3 were 100% and 70.1%, respectively. The highest accuracy (84.21%) was seen in combinations of at least 4 of 6 findings, with 80.00% sensitivity, 87.5% specificity, 83.33% PPV, and 84.85% NPV.

CONCLUSION

We suggested reliable imaging criteria with high specificity and accuracy for predicting the histopathologic grade of pNETs.

The Landmark Series: Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) comprise a heterogeneous group of neoplasms arising from pancreatic islet cells that remain relatively rare but are increasing in incidence worldwide. While significant advances have been made in recent years with regard to systemic therapies for patients with advanced disease, surgical resection remains the standard of care for most patients with localized tumors. Although formal pancreatectomy with regional lymphadenectomy is the standard approach for most PNETs, pancreas-preserving approaches without formal lymphadenectomy are acceptable for smaller tumors at low risk for lymph node metastases. Furthermore, observation of small, asymptomatic, low-grade PNETs is a safe, initial strategy and is generally recommended for tumors < 1 cm in size. In this Landmark Series review, we highlight the critical studies that have defined the surgical management of PNETs.

Radiomics Analysis Based on Diffusion Kurtosis Imaging and T2 Weighted Imaging for Differentiation of Pancreatic Neuroendocrine Tumors From Solid Pseudopapillary Tumors

Objective

To develop and validate a radiomics model of diffusion kurtosis imaging (DKI) and T2 weighted imaging for discriminating pancreatic neuroendocrine tumors (PNETs) from solid pseudopapillary tumors (SPTs).

Materials and Methods

Sixty-six patients with histopathological confirmed PNETs (n = 31) and SPTs (n = 35) were enrolled in this study. ROIs of tumors were manually drawn on each slice at T2WI and DWI (b = 1,500 s/mm²) from 3T MRI. Intraclass correlation coefficients were used to evaluate the interobserver agreement. Mean diffusivity (MD) and mean kurtosis (MK) were derived from DKI. The least absolute shrinkage and selection operator regression were used for feature selection.

Results

MD and MK had a moderate diagnostic performancewith the area under curve (AUC) of 0.71 and 0.65, respectively. A radiomics model, which incorporated sex and age of patients and radiomics signature of the tumor, showed excellent discrimination performance with AUC of 0.97 and 0.86 in the primary and validation cohort. Moreover, the new model had better diagnostic performance than that of MD (P = 0.023) and MK (P = 0.004), and showed excellent differentiation with a sensitivity of 95.00% and specificity of 91.67% in primary cohort, and the sensitivity of 90.91% and specificity of 81.82% in the validation cohort. The accuracy of radiomics analysis, radiologist 1, and radiologist 2 for diagnosing SPTs and PNETs were 92.42, 77.27, and 78.79%, respectively. The accuracy of radiomics analysis was significantly higher than that of subjective diagnosis (P < 0.05).

Conclusions

Radiomics model could improve the diagnostic accuracy of SPTs and PNETs and contribute to determining an appropriate treatment strategy for pancreatic tumors.

Pancreatic Neuroendocrine Neoplasms: 2020 Update on Pathologic and Imaging Findings and Classification

Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show characteristic clinical, histomorphologic, and prognostic features; genetic alterations; and biologic behavior. Up to 10% of panNENs develop in patients with syndromes that predispose them to cancer, such as multiple endocrine neoplasia type 1, von Hippel-Lindau disease, tuberous sclerosis complex, neurofibromatosis type 1, and glucagon cell adenomatosis. PanNENs are classified as either functioning tumors, which manifest early because of clinical symptoms related to increased hormone production, or nonfunctioning tumors, which often manifest late because of mass effect. PanNENs are histopathologically classified as well-differentiated pancreatic neuroendocrine tumors (panNETs) or poorly differentiated pancreatic neuroendocrine carcinomas (panNECs) according to the 2010 World Health Organization (WHO) classification system. Recent advances in cytogenetics and molecular biology have shown substantial heterogeneity in panNECs, and a new tumor subtype, well-differentiated, high-grade panNET, has been introduced. High-grade panNETs and panNECs are two distinct entities with different pathogenesis, clinical features, imaging findings, treatment options, and prognoses. The 2017 WHO classification system and the eighth edition of the American Joint Committee on Cancer staging system include substantial changes. Multidetector CT, MRI, and endoscopic US help in anatomic localization of the primary tumor, local-regional spread, and metastases. Somatostatin receptor scintigraphy and fluorine 18-fluorodeoxyglucose PET/CT are helpful for functional and metabolic assessment. Knowledge of recent updates in the pathogenesis, classification, and staging of panNENs and familiarity with their imaging findings allow optimal patient treatment. ^©RSNA, 2020.

Liver Tumor Burden in Pancreatic Neuroendocrine Tumors: CT Features and Texture Analysis in the Prediction of Tumor Grade and 18F-FDG Uptake

Pancreatic neuroendocrine tumors (p-NETs) are a rare group of neoplasms that often present with liver metastases. Histological characteristics, metabolic behavior, and liver tumor burden (LTB) are important prognostic factors. In this study, the usefulness of texture analysis of liver metastases in evaluating the biological aggressiveness of p-NETs was assessed. Fifty-six patients with liver metastases from p-NET were retrospectively enrolled. Qualitative and quantitative CT features of LTB were evaluated. Histogram-derived parameters of liver metastases were calculated and correlated with the tumor grade (G) and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) standardized uptake value (SUV). Arterial relative enhancement was inversely related with G (−0.37, p = 0.006). Different metastatic spread patterns of LTB were not associated with histological grade. Arterial_entropy was significantly correlated to G (−0.368, p = 0.038) and to Ki67 percentage (−0.421, p = 0.018). The ROC curve for the Arterial_entropy reported an area under the curve (AUC) of 0.736 (95% confidence interval 0.545–0.928, p = 0.035) in the identification of G1–2 tumors. Arterial_uniformity values were correlated to G (0.346, p = 0.005) and Ki67 levels (0.383, p = 0.033). Arterial_entropy values were directly correlated with the SUV (0.449, p = 0.047) which was inversely correlated with Arterial_uniformity (−0.499, p = 0.025). Skewness and kurtosis reported no significant correlations. In conclusion, histogram-derived parameters may predict adverse histological features and metabolic behavior of p-NET liver metastases.

ePAD: An Image Annotation and Analysis Platform for Quantitative Imaging

Medical imaging is critical for assessing the response of patients to new cancer therapies. Quantitative lesion assessment on images is time-consuming, and adopting new promising quantitative imaging biomarkers of response in clinical trials is challenging. The electronic Physician Annotation Device (ePAD) is a freely available web-based zero-footprint software application for viewing, annotation, and quantitative analysis of radiology images designed to meet the challenges of quantitative evaluation of cancer lesions. For imaging researchers, ePAD calculates a variety of quantitative imaging biomarkers that they can analyze and compare in ePAD to identify potential candidates as surrogate endpoints in clinical trials. For clinicians, ePAD provides clinical decision support tools for evaluating cancer response through reports summarizing changes in tumor burden based on different imaging biomarkers. As a workflow management and study oversight tool, ePAD lets clinical trial project administrators create worklists for users and oversee the progress of annotations created by research groups. To support interoperability of image annotations, ePAD writes all image annotations and results of quantitative imaging analyses in standardized file formats, and it supports migration of annotations from various propriety formats. ePAD also provides a plugin architecture supporting MATLAB server-side modules in addition to client-side plugins, permitting the community to extend the ePAD platform in various ways for new cancer use cases. We present an overview of ePAD as a platform for medical image annotation and quantitative analysis. We also discuss use cases and collaborations with different groups in the Quantitative Imaging Network and future directions.

Radiographic characteristics of neuroendocrine liver metastases do not predict clinical outcomes following liver resection

Background

Previous research has demonstrated that specific radiographic criteria, including the presence of calcifications and the enhancement pattern on computed tomography (CT) imaging, correlates with clinicopathologic features and outcomes of patients with gastroenteropancreatic neuroendocrine tumors (NET). We sought to investigate whether these radiographic characteristics were prognostic among patients with neuroendocrine liver metastases (NELM) undergoing surgical resection.

Methods

The preoperative contrast-enhanced CT scans of all patients who underwent resection of NELM at a single institution between 2000-2015 were retrospectively reviewed. The presence of calcifications was determined on non-contrast phase imaging. Enhancement on the arterial phase scan was categorized as hyperenhancing, hypoenhancing, or mixed. Relevant clinicopathologic characteristics as well as recurrence-free survival (RFS) and overall survival (OS) were compared between groups.

Results

Among 82 patients who underwent resection of NELM, 57 had available data on calcifications while 51 had data available on arterial enhancement patterns. Among all patients, median age was 58 (IQR: 47-63) and the majority were female (N=48, 59.5%). The most common primary tumor locations were pancreas (N=25, 30.5%) and small bowel (N=27, 32.9%). The most commonly performed operations were right hepatectomy (N=29, 35.4%), bisegmentectomy (N=15, 18.3%), and segmentectomy (N=14, 17.1%). Median tumor number was 4 (IQR: 2-9), median Ki-67 was 5% (IQR: 2-10%), and median size of the largest liver metastasis was 4.5 (IQR: 2.8-7.7) cm. Twelve (21%) patients had tumor calcifications. Among patients with and without calcifications there were no differences in demographics, clinicopathologic characteristics, RFS (P=0.772) or OS (P=0.095). Arterial enhancement was hypoenhancing in 23 (45.1%), hyperenhancing in 10 (19.6%), and mixed in 18 (35.3%). Similarly, there were no differences between arterial enhancement groups in demographics, clinicopathologic characteristics, RFS (P=0.618) or OS (P=0.268).

Conclusions

Radiographic characteristics on contrast-enhanced CT are not associated with the outcomes of patients undergoing resection of NELM. Future investigations should evaluate the prognostic impact of functional neuroendocrine imaging.

Quantitative 3D Assessment of 68Ga-DOTATOC PET/MRI with Diffusion-Weighted Imaging to Assess Imaging Markers for Gastroenteropancreatic Neuroendocrine Tumors: Preliminary Results

⁶⁸Ga-DOTATOC PET/MRI combines the advantages of PET in the acquisition of metabolic-functional information with the high soft-tissue contrast of MRI. SUVs in tumors have been suggested to be a measure of somatostatin receptor expression. A challenge with receptor ligands is that the distribution volume is confined to tissues with tracer uptake, potentially limiting SUV quantification. In this study, various functional 3-dimensional SUV apparent diffusion coefficient (ADC) parameters and arterial tumor enhancement were tested for ability to characterize gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). Methods: For this single-center, cross-sectional study, 22 patients with 24 histologically confirmed GEP NET lesions (15 men and 7 women; median age, 61 y; range, 43-81 y) who underwent hybrid ⁶⁸Ga-DOTA PET/MRI at 3 T between January 2017 and July 2019 met the eligibility criteria. SUV, tumor-to-background ratio, total functional tumor volume, and mean and minimum ADC were measured on the basis of volumes of interest and examined with receiver-operating-characteristic analysis to determine cutoffs for differentiation between low- and intermediate-grade GEP NETs. The Spearman rank correlation coefficient was used to assess correlations between functional imaging parameters. Results: The ratio of PET-derived SUV_mean and diffusion-weighted imaging-derived minimum ADC was introduced as a combined variable to predict tumor grade, outperforming single predictors. On the basis of a threshold ratio of 0.03, tumors could be classified as grade 2 with a sensitivity of 86% and a specificity of 100%. SUV and functional ADCs, as well as arterial contrast enhancement parameters, showed nonsignificant and mostly negligible correlations. Conclusion: Because receptor density and tumor cellularity appear to be independent, potentially complementary phenomena, the combined ratio of PET/MRI and SUV_mean/ADC_min may be used as a novel biomarker allowing differentiation between grade 1 and grade 2 GEP NETs.

The added value of intravoxel incoherent motion diffusion weighted imaging parameters in differentiating high-grade pancreatic neuroendocrine neoplasms from pancreatic ductal adenocarcinoma

The aim of the present study was to investigate the potential significance of intravoxel incoherent motion (IVIM)-diffusion weighted imaging (DWI) in differentiating high-grade pancreatic neuroendocrine neoplasms (pNENs) from pancreatic ductal adenocarcinoma (PDAC). A total of 50 patients, including 37 patients with PDAC and 13 patients with high-grade pNENs, underwent pancreatic multiple b-values DWI with 15 b-values including 0, 10, 20, 40, 60, 80, 100, 150, 200, 400, 800, 1,000, 1,200, 1,500 and 2,000 sec/mm². Standard apparent diffusion coefficient (ADC_standard) and IVIM parameter [slow apparent diffusion coefficient (D_slow), fast apparent diffusion coefficient (D_fast), fraction of fast apparent diffusion coefficient (ƒ)] values of PDAC and pNENs were compared. P<0.05 was considered to indicate a statistically significant difference. Receiver operating characteristics analysis was performed in order to evaluate the diagnostic potential of IVIM parameters for differentiating high-grade pNENs from PDAC. D_slow of pNENs was significantly lower compared with that of PDAC (0.460 vs. 0.579×10⁻³ mm²/sec; P=0.001). D_fast of pNENs was significantly higher compared with that of PDAC (13.361 vs. 4.985×10⁻³ mm²/sec; P<0.001). Area under the curve of D_slow, D_fast and combined D_slow and D_fast was 0.793, 0.863 and 0.885 respectively. The specificity and sensitivity of D_slow≤0.472×10⁻³ mm²/sec were 97.3 and 53.9%, respectively, for differentiating high-grade pNENs from PDAC. The specificity and sensitivity of D_fast >9.58×10⁻³ mm²/sec were 91.9 and 69.2%, respectively, for differentiating high-grade pNENs from PDAC. When D_slow and D_fast were combined, the specificity and sensitivity for differentiating high-grade pNENs from PDAC were 76.9 and 100%, respectively. Taken together, these results indicated that the diffusion-associated parameter D_slow and the perfusion-associated parameter D_fast of IVIM-DWI may differentiate high-grade pNENs from PDAC with high diagnostic accuracy, and that IVIM-DWI may be a valuable biomarker in differentiating pancreatic neoplasms.

Pancreatic neuroendocrine tumors

PURPOSE OF REVIEW

Pancreatic neuroendocrine tumors (pNETs) are a rare, heterogeneous group of pancreatic neoplasms with a wide range of malignant potential. They may manifest as noninfiltrative, slow-growing tumors, locally invasive masses, or even swiftly metastasizing cancers.

RECENT FINDINGS

In recent years, because of the increasing amount of scientific literature available for pNETs, the classification, prognostic stratification criteria, and available consensus guidelines for diagnosis and therapy have been revised and updated.

SUMMARY

The vast majority of new pNET diagnoses consist of incidentally discovered lesions on cross-sectional imaging. The biologic behavior of pNETs is defined by the grade and stage of the tumor. Surgery is the only curative treatment and it, therefore, represents the first therapeutic choice for any localized pNET; however, recent evidence suggests that patients with small (<2 cm), nonfunctioning G1 tumors can be safely observed.An aggressive surgical approach towards liver metastases is recommended in selected cases, as well as liver-directed therapies for disease control. In the presence of unresectable progressive disease, somatostatin analogs, targeted therapies such as everolimus, peptide receptor radionuclide therapy, and systemic chemotherapy are all useful tools for prolonging survival.

Ki-67 Index of 5% is Better Than 2% in Stratifying G1 and G2 of the World Health Organization Grading System in Pancreatic Neuroendocrine Tumors

OBJECTIVE

The World Health Organization (WHO) grading system for the stratification of G1 and G2 pancreatic neuroendocrine tumors (pNETs) using an optimal Ki-67 index cutoff is still controversial. The present study aimed at finding one optimal Ki-67 cutoff value that distinguishes G1 and G2 tumors by analyzing the prognosis of patients with pNET in our center.

METHODS

Data from 84 patients with pNET undergoing surgical resection in The First Affiliated Hospital of Sun Yat-sen University between March 2003 and October 2015 were retrospectively analyzed.

RESULTS

The 5-year overall survival rate was 74.2%. Univariate analysis revealed that functional secretion, WHO grade, and TNM stage were significantly associated with long-term survival (all P < 0.05). Multivariate analysis demonstrated that WHO grade (P = 0.023) and TNM stage (P = 0.040) were independent prognostic factors. The receiver operating characteristic curve showed that the Ki-67 index of 5% had the best predictive ability (76.7%) for 5-year survival with a hazard ratio of 44.7. The hazard ratio was only 8.14 when the Ki-67 index cutoff was 2%.

CONCLUSIONS

TNM stage and WHO grade were independent prognostic factors of pNETs. A Ki-67 index of 5% is better than 2% in stratifying G1 and G2 pNET tumors.

Pancreatic neuroendocrine tumors: MR imaging features preoperatively predict lymph node metastasis

PURPOSES

Predictive factors of lymph node metastasis (LNM) in pancreatic neuroendocrine tumors (pNETs) are not well established. We sought to identify the value of MR imaging features in preoperatively predicting the lymph node metastasis of pNETs.

MATERIALS AND METHODS

In this study, we enrolled 108 consecutive patients with pNETs between January 2009 and June 2018. MR morphologic features and quantitative data were evaluated. Predictors of LNM were evaluated using univariate and multivariate logistic regression models.

RESULTS

A total of 108 patients with pNETs were finally enrolled, including 82 LNM-negative and 26 LNM-positive patients. Features significantly related to the LNM of pNETs at univariate analysis were tumor size > 2 cm (P = 0.003), Ki-67 > 5% (P = 0.002), non-enhancement pattern (P < 0.001), apparent diffusion coefficient value (P < 0.001), main pancreatic duct dilation (P < 0.001) and pancreatic atrophy (P = 0.032) and extrapancreatic tumor spread (P = 0.001), CNRs during arterial, portal and delay phase (P = 0.005, 0.047, and 0.045, respectively), and histological classification (P = 0.006). At multivariate analysis, non-enhancement pattern (P = 0.019; odds ratio, 6.652; 95% CI 1.369, 32.321) and main pancreatic duct dilation (P = 0.018; odds ratio, 6.745; 95% CI 1.379, 32.991) were independent risk factors for predicting the LNM of pNETs.

CONCLUSION

The non-enhancement characteristic and main pancreatic duct dilation appear to be linked with LNM in pNETs. These radiological predictors can be easily obtained preoperatively, and may help to avoid missing pNETs with a high risk of LNM.

Differentiation of hypovascular pancreatic neuroendocrine tumors from pancreatic ductal adenocarcinoma using contrast-enhanced computed tomography

Hypovascular pancreatic neuroendocrine tumors (hypo-PNETs) are often misdiagnosed as pancreatic ductal adenocarcinoma (PDAC). However, the treatment options and prognosis of PNETs and PDAC are substantially different. This retrospective study differentiated hypo-PNETs from PDAC using contrast-enhanced CT (CE-CT). Clinical data and CE-CT findings, including tumor location, size, boundary, pancreatic duct dilatation, local invasion or metastases, tumor contrast enhancement, and tumor-to-pancreas enhancement ratio, were compared between 39 PDACs and 18 hypo-PNETs. At CT imaging, hypo-PNETs showed a higher frequency of a well-defined margin and lower frequencies of pancreatic duct dilatation and local invasion or metastasis when compared with PDAC (p < 0.05 for all). The mean attenuation of hypo-PNETs at the arterial and portal venous phase was significantly higher than that of PDAC (p < 0.001, p = 0.003, respectively). Similar results were observed in tumor-to-pancreas enhancement ratio. Tumor attenuation and tumor-to-pancreas enhancement ratio at the arterial phase showed the largest area under the curve (AUC) of 0.888 and 0.812 with 83.3–88.9% of sensitivity and 61.6–77.0% of specificity. Pancreatic duct dilatation, local invasion or metastasis, and tumor attenuation at the portal venous phase also showed acceptable AUC (0.703–0.748). Thus CE-CT features, especially the enhancement degree at the arterial phases, may be useful for differentiating hypo-PNETs from PDAC using CE-CT.

EUS-guided radiofrequency ablation as an alternative to surgery for pancreatic neuroendocrine neoplasms: Who should we treat?

Pancreatic neuroendocrine neoplasms (PanNENs) are rare tumors, but their incidental diagnosis has significantly increased due to the widespread use of imaging studies. Therefore, most PanNENs are now diagnosed when completely asymptomatic and in early stages. PanNENs are classified according to their grade (Ki-67 index) and can be functional (F-) or nonfunctional (NF-) depending on the presence or absence of a clinical, hormonal hypersecretion syndrome. The mainstay treatment of PanNENs is a surgery that is mostly curative but also associated with significant short- and long-term adverse events. Therefore, less invasive alternative locoregional treatment modalities are warranted. Recently, few case reports and two case series have described EUS-guided radiofrequency ablation (EUS-RFA) for the treatment of patients with both F-PanNENs and NF-PanNENs. If for F-PanNENs EUS-RFA can very easily become the standard of care, for NF-PanNENEs it is still controversial how to select patients for EUS-RFA. A balance between overtreatment (i.e., RFA/surgery in patients who will not progress) and undertreatment (locoregional treatments in patients with undetected metastases) needs to be found based on solid data. The decision should also take into account patients’ comorbidity and risk of postoperative death, life expectancy, tumor location, risk of postoperative fistula and postoperative morbidity, and risk of long-term exocrine and/or endocrine insufficiency. To answer the important question on which a patient should be treated with EUS-RFA, properly designed studies to evaluate the efficacy of this treatment in large cohorts of patients with NF-PanNENs and to establish prognostic factors associated with treatment response are urgently needed.

Natural History of Small Pancreatic Lesions Suspected to Be Nonfunctioning Pancreatic Neuroendocrine Tumors

OBJECTIVES

Nonfunctioning pancreatic neuroendocrine tumors (NF-PNETs) are a rare disease but have been diagnosed more frequently than before. The aim of this study was to evaluate the natural course of small NF-PNETs.

METHODS

We performed a retrospective analysis of patients with incidentally found small NF-PNETs (<20 mm) from 1999 to 2015. The patients who were recommended surveillance were included.

RESULTS

There were 69 patients with small NF-PNETs with a mean size of 10.9 (standard deviation [SD], 3.1) mm. The average follow-up period was 52.2 (SD, 38.7) months. The changes in tumor size were as follows: increased (13.0%), sustained (84.1%), and decreased (2.9%). Eighteen were evaluated with grade 1 NF-PNETs and 1 with grade 2 among the obtained tissues. Thirteen patients underwent surgery after an average 32.9 (SD, 42.6) months later. There were 7 patients of Ia, 1 of Ib, 2 of IIa, and 1 of IIb according to the pathologic stages. Two patients received reoperation for recurrent tumors, and 2 patients showed distant metastasis after surgery, but no disease-related death occurred.

CONCLUSIONS

Most of the small NF-PNETs did not increase in size and seldom showed metastasis. The wait-and-see strategy can be used for NF-PNETs less than 2 cm.

Nonhypervascular pancreatic neuroendocrine tumors: Spectrum of MDCT imaging findings and differentiation from pancreatic ductal adenocarcinoma

PURPOSE

The purpose of our study was to determine contrast-enhanced MDCT features to differentiate nonhypervascular pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal adenocarcinomas (PDACs).

METHODS

and materials: We included 74 patients with PNETs and 80 patients with PDACs who underwent preoperative MDCT. Two radiologists evaluated the morphologic characteristic and enhancement patterns of the tumors. Quantitative and qualitative analysis was performed, including evaluation of tumor size, homogeneity, contrast enhancement pattern, presence of pancreatic duct dilatation and tumor invasion to the adjacent vessels and peripancreatic infiltration. Tumor-to-pancreas enhancement ratio was defined as the Hounsfield units (HU) value of the tumor divided by the HU value of the pancreas. the first group was hypervascular PNETs showing hyperenhancement on arterial phase images and nonhypervascular PNETs, showing iso- or hypoenhancement on arterial phase images. After that, two radiologists estimated the possibilities of PNET or PDAC were for nonhypervascular PNETs.

RESULTS

On the basis of arterial enhancement, 43 PNETs were hypervascular and 31 were nonhypervascular. When compared to PDAC, nonhypervascular PNETs more frequently had well-defined tumor margins, intratumoral cystic components, calcifications and blood vessels and less frequently had main pancreatic duct dilatation, peripancreatic infiltration and vascular invasion (p < 0.01 for all). Nonhypervascular PNETs had higher tumor-to-pancreas enhancement ratio in venous phase (1.02 vs. 0.78, p = 0.012). Nonhypervascular PNETs more often had portal-venous hyperenhancement or persistent isoenhancement, while PDAC more often had persistent hypoenhancement or gradual delayed enhancement (p < 0.001). The absence of pancreatic duct dilatation and portal-venous hyperenhancement or persistent isoenhancement were the independent predictors for nonhypervascular PNETs. (The most accurate MDCT-findings to predict nonhypervascular PNET were the absence of pancreatic duct dilatation and peripancreatic infiltration (79% and 92% accuracy), portal-venous phase hyperenhancement or persistent isoenhancement (77%), the presence of intratumoral blood vessels (77%) and relative enhancement intensity in venous phase >0.9 (76%). Using these criteria, the area under curve for differentiation of PNET from PDAC was 0.906-0.846.

CONCLUSION

Combined assessment of the enhancement and morphologic characteristics can improve the differentiation between nonhypervascular PNETs and PDAC at contrast-enhanced MDCT.

Association between pathologic grade and multiphase computed tomography enhancement in pancreatic neuroendocrine neoplasm

BACKGROUND AND AIM

Pancreatic neuroendocrine neoplasms (PanNENs) are rare diseases but gradually increasing in prevalence with different prognosis. Multiphase contrast-enhanced computed tomography (CT) is known as widely used imaging modality for the diagnosis of pancreatic tumors. We aimed to investigate whether CT enhancement pattern is associated with the pathologic tumor grade and can predict that of PanNEN.

METHODS

Ninety PanNEN patients who underwent multiphase enhanced CT before pathologic diagnosis were retrospectively reviewed. CT enhancement values at each phase were measured, and its relation with pathologic grade was assessed.

RESULTS

Ninety PanNENs included 62 G1 (68.9%), 21 G2 (23.3%), and 7 G3 (7.8%). The enhancement values of the early arterial phase were significantly different among three groups (G1 119.4 HU, G2 94.7 HU, and G3 64.8 HU; G1 vs G2, P = 0.043; G1 vs G3, P = 0.001; and G2 vs G3, P = 0.027). In the late arterial phase, there was a difference between grade 1/2 and 3 but no significant difference between grade 1 and grade 2 (G1 164.3 HU, G2 142.9 HU, and G3 94.1 HU; G1 vs G2, P = 0.804; G1 vs G3, P = 0.016; and G2 vs G3, P = 0.022). The enhancement value of the portal phase did not differ significantly among the three groups. Diagnostic ability of the early arterial enhancement value for the differentiation of the G1 (cutoff 109.5 HU, sensitivity 73.3%, and specificity 62.5%) was comparable with that of the tumor size (cutoff 20.5 mm, sensitivity 68.9%, and specificity 66.7%).

CONCLUSIONS

Computed tomography enhancement value at early arterial phase and its changing pattern can be a useful predictor for the differentiation of pathologic grade of PanNENs.

Prediction of lymph node metastasis in pancreatic neuroendocrine tumors by contrast enhancement characteristics

BACKGROUND

Iso- or hypo-attenuating areas in the arterial phase on contrast-enhanced computed tomography (CE-CT) have been reported to be negative prognostic features in pancreatic neuroendocrine tumors (PNETs). Given that the optimal indication for lymph node dissection in patients with PNET remains unclear, we sought to utilize enhancement characteristics on CE-CT as a preoperative predictor of regional lymph node metastasis in PNETs.

METHODS

The medical records of patients with well-differentiated PNETs who underwent pancreatectomy along with lymphadenectomy were retrospectively analyzed. We divided PNETs into two groups based on the extent of attenuation in the late arterial phase on CE-CT imaging. PNETs that showed hyper-attenuation over the entire area compared to the adjacent normal pancreas were categorized as hyper-PNETs. PNETs that contained both hyper and iso- or hypo-attenuation regions as well as those that showed only iso- or hypo-attenuation over the entire area were categorized as hetero/hypo-PNETs.

RESULTS

Forty-one patients with a median age of 64 years were enrolled, including 11 with hyper-PNETs and 30 with hetero/hypo-PNETs. Hetero/hypo-PNETs were significantly larger than hyper-PNETs (P = 0.022), and the former group more frequently comprised G2 tumors, according to the World Health Organization 2010 classification (P < 0.001). On univariate and multivariate analyses, hetero/hypo-PNETs were independently associated with regional lymph node metastasis.

CONCLUSIONS

The presence of iso- or hypo-attenuating regions appears to be associated with regional lymph node metastasis in PNETs. Tumor enhancement characteristics should be assessed in patients with PNET so as not to miss those at high risk of lymph node metastasis.

Imaging of secretory tumors of the gastrointestinal tract

Gastrointestinal secretory tumors, or gastroenteropancreatic neuroendocrine tumors, encompass a wide array of endocrine cell tumors. The significance of these tumors lies in their ability to alter physiology through hormone production as we well as in their malignant potential. Functioning tumors may present earlier due to symptomatology; conversely, non-functioning tumors are often diagnosed late as they reach large sizes, causing symptoms secondary to local mass effect. Imaging aids in the diagnosis, staging, and prognosis and provides key information for presurgical planning. Although most of these tumors are sporadic, some are associated with important syndromes and associations, knowledge of which is critical for patient management. In this article, we provide an overview of secretory and neuroendocrine tumors of the GI tract and pancreas.

Vascularity and Tumor Size are Significant Predictors for Recurrence after Resection of a Pancreatic Neuroendocrine Tumor

BACKGROUND

It is difficult to identify patients at high risk of recurrence after pancreatectomy for pancreatic neuroendocrine tumor (PNET) using only the grading classification, especially the G2 category, which includes both benign and low- and high-grade malignant tumors.

METHODS

Forty-one patients with PNET who underwent pancreatectomy were enrolled in this study. We defined the computed tomography (CT) ratio as the CT value of the tumor divided by that of non-tumorous pancreatic parenchyma using the late arterial phase dynamic CT. The optimal cut-off values for CT ratio and tumor size were determined using p-values that were calculated using the log-rank test.

RESULTS

The optimal cut-off values of CT ratio and tumor size for dividing patients into groups according to the greatest difference in disease-free survival (DFS) were 0.85 (p < 0.001) and 3.0 cm (p < 0.001), respectively. In analysis using Spearman's correlation coefficient, CT ratio (p = 0.007) and tumor size (p = 0.003) were individually associated with the Ki-67 proliferative index. Cox proportional hazard analysis identified that a CT ratio <0.85 (n = 10, p = 0.006) and tumor size ≥3.0 cm (n = 13, p = 0.023) were independent prognostic factors associated with DFS. All patients in the CT ratio ≥0.85 and tumor size <3.0 cm group (n = 23, including seven patients with G2 disease) did not develop recurrence after surgery. On the other hand, 5-year DFS in the CT ratio <0.85 and tumor size ≥3.0 cm group (n = 5, including three patients with G2 disease) was zero.

CONCLUSIONS

PNETs with a CT ratio <0.85 and tumor size ≥3.0 cm should be considered as having a high risk of recurrence after pancreatectomy.

Nonfunctioning, small, incidental pancreatic neuroendocrine tumors: Results of a nonoperative approach cohort

OBJECTIVE

The availability of new imaging techniques has conditioned an increase in the incidental diagnosis of small nonfunctioning pancreatic neuroendocrine tumors (PNET-NF). The best treatment is controversial, some authors advise a conservative approach in selected cases. Our aim is to analyze the evolution of incidental, small size PNET-NF, treated with clinical follow-up without surgery.

METHODS

We performed a retrospective analysis of a prospective database of patients diagnosed incidentally with PNET-NF since November 2007 to September 2015. We include those with PNET-NF ≤2cm and asymptomatic. The diagnosis was performed using imaging tests indicating endoscopic ultrasound-guided fine-needle aspiration in case of doubts in the diagnosis. The follow-up was performed at our center, registering clinical and/or radiological changes.

RESULTS

We included 24 patients with a median age of 70 years, and a similar distribution in terms of sex. The diagnosis was made through computed tomography multidetector or magnetic resonance imaging and octreotide scan. The tumors were located mainly in the head and neck (46%), with a mean size of 11,5±3,55mm at diagnosis (5-19mm). In 2 cases endoscopic ultrasound fine needle aspiration was used (8%), confirming the diagnosis of low-grade PNET with Ki67<5%. The median follow-up was 39 months (7-100). In 19 patients (79%) they remained the same size, 21% (5) increased its size with a mean of 2,6±2mm (1-6). No cases had progression of disease.

CONCLUSION

In selected patients, non-surgical management of PNET-NF is an option to consider, when they are asymptomatic and ≤2cm. Larger studies with more patients and more time of follow-up are needed to validate this non-operative approach.

Imaging in pancreatic disease

Pancreatic diseases, chronic pancreatitis, pancreatic cancer and diabetes mellitus, taken together, occur in >10% of the world population. Pancreatic diseases, as with other diseases, benefit from early intervention and appropriate diagnosis. Although imaging technologies have given clinicians an unprecedented toolbox to aid in clinical decision-making, advances in these technologies and development of molecular-based diagnostic tools could enable physicians to identify diseases at an even earlier stage and, thereby, improve patient outcomes. In this Review, we discuss and identify gaps in the use of imaging techniques for the early detection and appropriate treatment stratification of various pancreatic diseases, including diabetes mellitus, acute and chronic pancreatitis and pancreatic cancer. Imaging techniques discussed are MRI, CT, PET and ultrasonography. Additionally, the identification of new molecular targets for imaging and the development of contrast agents that are able to give molecular information in noninvasive radionuclear imaging and ultrasonography are emerging areas of innovation that could lead to increased diagnostic accuracy and improved patient outcomes.

Nonhypervascular Pancreatic Neuroendocrine Tumors: Differential Diagnosis from Pancreatic Ductal Adenocarcinomas at MR Imaging-Retrospective Cross-sectional Study

Purpose To determine useful magnetic resonance (MR) imaging features to differentiate nonhypervascular pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal adenocarcinomas (PDACs). Materials and Methods The institutional review board approved this retrospective study and waived the informed consent requirement. Seventy-four patients with surgically confirmed PNETs and 82 patients with PDACs who underwent gadobutrol-enhanced MR imaging were included. Two radiologists independently evaluated the morphologic characteristics and temporal enhancement patterns of each tumor. Quantitative analysis, including measurement of tumor size, maximal upstream parenchymal thickness (MUPT), contrast-to-noise ratio, and apparent diffusion coefficient values, was performed. Uni- and multivariate logistic regression analyses were performed to identify relevant features to differentiate between PNETs and PDACs. Results On the basis of arterial enhancement, 38 PNETs (51%, 38 of 74) were hypervascular and 36 PNETs (49%, 36 of 74) were nonhypervascular. At MR imaging, nonhypervascular PNETs showed significantly higher frequencies of a well-defined margin, portal hyper- or isoenhancement, and MUPT of 10 mm or greater but lower frequencies of ductal dilatation, vascular invasion, and peripancreatic infiltration when compared with PDACs (P < .05 for all). At multivariate analysis, a well-defined margin and portal hyper- or isoenhancement were independent significant differentiators of PNETs from PDACs (odds ratio, 20.3 and 16.1, respectively). When applying the criteria of a well-defined margin and portal hyper- or isoenhancement, 64% of sensitivity and 99% of specificity were observed for the differential diagnosis of PNETs from PDACs. Conclusion A well-defined margin and hyper- or isoenhancement in the portal venous phase are useful MR imaging features that are more common in nonhypervascular PNETs and may help discriminate nonhypervascular PNETs from PDACs. ^© RSNA, 2017 Online supplemental material is available for this article.

Indications for Surgical Resection in Low-Grade Pancreatic Neuroendocrine Tumors

The role of surgical resection in low-grade pancreatic neuroendocrine tumors (P-NET) is unclear. The patients diagnosed with low-grade P-NET from 1988 to 2012 were identified in SEER. Five hundred and sixty-one patients met the inclusion criteria. A majority were white (82.9%), and node negative (69.9%). Univariate analysis revealed that tumor size (<2 cm 8.3%, 2–4 cm 38.5%, and >4 cm 40.3%; P < 0.0001) and surgery (30.9% vs 25.3%; P = 0.0014) were associated with the risk of lymph node metastases (LNM). In contrast, age ( P = 0.8360), gender ( P = 0.4903), and race ( P = 0.4235) were not. Five-year disease-free survival was associated with size (<2 cm 89.4%, 2–4 cm 80.0%, and >4 cm 74.5%; P = 0.0089), LNM (72.4% vs 82.9%; P = 0.0025), and surgery (84.3% vs 47.5%; P < 0.0001). Cox regression model showed that the association with LNM ( P = 0.0025) and surgery ( P < 0.0001) was significant. Surgery was associated with an improved disease-free survival for tumors >2 cm (2–4 cm, 84.4% vs 26.0% at five years; P = 0.0003, and >4 cm, 80.5% vs 49.5% at five years; P < 0.0001) but not for those with tumor size <2 cm ( P = 0.4525). In conclusions, low-grade P-NETs in patients with tumor size >2 cm showed an increased risk of LNM and improved survival with resection.

Islet Cell Tumors of the Pancreas

Islet cell tumors of the pancreas, also known as pancreatic neuroendocrine tumors, constitute less than 5% of pancreatic tumors, and 7% of all neuroendocrine tumors. Most are non-functional, and patients often present with metastatic disease. Functional tumors present with distinct clinical syndromes. Accurate staging is critical as surgery is both the cornerstone of treatment, and the only hope for cure. Medical management involves treating the manifestations of hormonal excess, and using somatastatin analogues when appropriate. Systemic chemotherapy, targeted molecular therapy, and peptide receptor radiotherapy may be used for refractory disease in lieu of or as an adjunct to surgery.

Contrast-enhancement ratio on multiphase enhanced computed tomography predicts recurrence of pancreatic neuroendocrine tumor after curative resection

BACKGROUND/OBJECTIVE

No previous study has quantitatively investigated the degree of enhancement of pancreatic neuroendocrine tumors (pNETs) using a routine preoperative modality. The aim of this study was to evaluate the contrast-enhancement ratio (CER) of pNETs using multiphase enhanced CT and to assess the impact of the CER on disease recurrence after surgery.

METHODS

A retrospective study was performed using data from 47 consecutive patients with pNETs who had undergone curative surgery. The CER of the tumor was calculated by dividing the CT attenuation value obtained during the maximum-enhanced phase by that obtained during the pre-enhanced phase. A region of interest was placed in the largest tumor dimension plane so as to cover as much surface of the tumor as possible while avoiding adjacent normal structures, calcification, and necrotic areas of the tumor.

RESULTS

During a median follow-up period of 51 months (range, 1-132 months), a total of 4 patients (8.5%) developed disease recurrence. The median CER value was significantly lower for the patients with recurrence than for the patients without recurrence (2.9 vs. 4.3, P = 0.013). Univariate analyses showed that a CER ≤3.2 was significantly associated with disease recurrence (P < 0.001). All the patients with disease recurrence had tumors that were both large (>20 mm) and weakly enhanced (CER ≤ 3.2), whereas no recurrences were observed even in patients with tumors >20 mm when the CER was greater than 3.2.

CONCLUSIONS

CER might be a useful predictor of disease recurrence in patients with pNETs.

Imaging of pancreatic neoplasms

Ductal adenocarcinoma accounts for 85% to 90% of all solid pancreatic neoplasms, is increasing in incidence, and is the fourth leading cause of cancer-related deaths. There are currently no screening tests available for the detection of ductal adenocarcinoma. The only chance for cure in pancreatic adenocarcinoma is surgery. Imaging has a crucial role in the identification of the primary tumor, vascular variants, identification of metastases, disease response assessment to treatment, and prediction of respectability. Pancreatic neuroendocrine neoplasms can have a distinctive appearance and pattern of spread, which should be recognized on imaging for appropriate management of these patients.

Non-functional neuroendocrine tumors of the pancreas: Advances in diagnosis and management

Nonfunctional neuroendocrine tumors of the pancreas (NF-PNETs) are a heterogeneous group of neoplasms. Although rare, the incidence of NF-PNETs is increasing significantly. The classification of PNETs has evolved over the past decades and is now based on a proliferation grading system. While most NF-PNETs are slow growing, tumors with more aggressive biology may become incurable once they progress to unresectable metastatic disease. Tumors of higher grade can be suspected preoperatively based on the presence of calcifications, hypoenhancement on arterial phase computed tomography, positron emission technology avidity and lack of octreotide scan uptake. Surgery is the only curative treatment and is recommended for most patients for whom complete resection is possible. Liver-directed therapies (thermal ablation, transarterial embolization) can be useful in controlling unresectable hepatic metastatic disease. In the presence of unresectable progressive disease, somatostatin analogues, everolimus and sunitinib can prolong progression-free survival. This article provides a comprehensive review of NF-PNETs with special emphasis on recent advances in diagnosis and management.

Pancreatic neuroendocrine tumors containing areas of iso- or hypoattenuation in dynamic contrast-enhanced computed tomography: Spectrum of imaging findings and pathological grading

PURPOSE

To evaluate dynamic contrast-enhanced computed tomography (CT) features of pancreatic neuroendocrine tumors (PNETs) containing areas of iso- or hypoattenuation and the relationship with pathological grading.

MATERIALS AND METHODS

Between June 2006 and March 2014, 61 PNETs in 58 consecutive patients (29 male, 29 female; median-age 55 years), which were surgically diagnosed, underwent preoperative dynamic contrast-enhanced CT. PNETs were classified based on contrast enhancement patterns in the pancreatic phase: iso/hypo-PNETs were defined as tumors containing areas of iso- or hypoattenuation except for cystic components, and hyper-PNETs were tumors showing hyperattenuation over the whole area. CT findings and contrast-enhancement patterns of the tumors were evaluated retrospectively by two radiologists and compared with the pathological grading.

RESULTS

Iso/hypo-PNETs comprised 26 tumors, and hyper-PNETs comprised 35 tumors. Not only hyper-PNETs but also most iso/hypo-PNETs showed peak enhancement in the pancreatic phase and a washout from the portal venous phase to the delayed phase. Iso/hypo-PNETs showed larger tumor size than the hyper-PNETs (mean, 3.7 cm vs. 1.6 cm; P<0.001), and were significantly correlated with unclear tumor margins (n=4 vs. n=0; P=0.029), the existence of cystic components (n=10 vs. n=3; P=0.006), intratumoral blood vessels in the early arterial phase (n=13 vs. n=3; P<0.001), and a smooth rim enhancement in the delayed phase (n=12 vs. n=6; P=0.019). Iso/hypo-PNETs also showed significantly higher pathological grading (WHO 2010 classification; iso/hypo, G1=14, G2=11, G3=1; hyper, G1=34, G2=1; P<0.001).

CONCLUSION

PNETs containing iso/hypo-areas showed a rapid enhancement pattern as well as hyper-PNETs, various radiological features and higher malignant potential.

Pancreatic neuroendocrine tumour (PNET): Staging accuracy of MDCT and its diagnostic performance for the differentiation of PNET with uncommon CT findings from pancreatic adenocarcinoma

PURPOSE

To investigate staging accuracy of multidetector CT (MDCT) for pancreatic neuroendocrine tumour (PNET) and diagnostic performance for differentiation of PNET from pancreatic adenocarcinoma.

MATERIAL AND METHODS

We included 109 patients with surgically proven PNET (NETG1 = 66, NETG2 = 31, NEC = 12) who underwent MDCT. Two reviewers assessed stage and presence of predefined CT findings. We analysed the relationship between CT findings and tumour grade. Using PNETs with uncommon findings, we also estimated the possibility of PNET or adenocarcinoma.

RESULTS

Accuracy for T stage was 85-88% and N-metastasis was 83-89%. Common findings included well circumscribed, homogeneously enhanced, hypervascular mass, common in lower grade tumours (p < 0.05). Uncommon findings included ill-defined, heterogeneously enhanced, hypovascular mass and duct dilation, common in higher grade tumours (p < 0.05). Using 31 PNETs with uncommon findings, diagnostic performance for differentiation from adenocarcinoma was 0.760-0.806. Duct dilatation was an independent predictor for adenocarcinoma (Exp(B) = 4.569). PNETs with uncommon findings were associated with significantly worse survival versus PNET with common findings (62.7 vs. 95.7 months, p < 0.001).

CONCLUSION

MDCT is useful for preoperative evaluation of PNET; it not only accurately depicts the tumour stage but also prediction of tumour grade, because uncommon findings were more common in higher grade tumours.

KEY POINTS

• CT accurately depicts the T stage and node metastasis of PNET. • Uncommon findings were more common in higher grade tumours. • CT information may be beneficial for optimal therapeutic planning.

Multiple Endocrine Neoplasia: Genetics and Clinical Management

Early diagnosis of multiple endocrine neoplasia (MEN) syndromes is critical for optimal clinical outcomes; before the MEN syndromes can be diagnosed, they must be suspected. Genetic testing for germline alterations in both the MEN type 1 (MEN1) gene and RET proto-oncogene is crucial to identifying those at risk in affected kindreds and directing timely surveillance and surgical therapy to those at greatest risk of potentially life-threatening neoplasia. Pancreatic, thymic, and bronchial neuroendocrine tumors are the leading cause of death in patients with MEN1 and should be aggressively considered by at least biannual computed tomography imaging.