Pancreatic neuroendocrine tumors: a comprehensive review

Prospective study on stereotactic body radiotherapy for small pancreatic neuroendocrine tumors: tolerance and effectiveness analysis

INTRODUCTION

Surgery is the standard treatment for pancreatic neuroendocrine tumors (pNETs), obtaining favorable results but associating high morbidity and mortality rates. This study assesses stereotactic body radiation therapy (SBRT) as a radical approach for small (< 2 cm) nonfunctioning pNETs.

MATERIALS AND METHODS

From January 2017 to June 2023, 20 patients with small pNETs underwent SBRT in an IRB-approved study. Endpoints included local control, tolerance, progression-free survival, and overall survival (OS). Diagnostic assessments comprised endoscopy, CT scans, OctreScan or PET-Dotatoc, abdominal MRI, and histological confirmatory samples.

RESULTS

In a 30-month follow-up of 20 patients (median age 55.5 years), SBRT was well-tolerated with no grade > 2 toxicity. 40% showed morphological response, 55% remained stable. Metabolically, 50% achieved significant improvement. With a median OS of 41.5 months, all patients were alive without local or distant progression or need for surgical resection.

CONCLUSION

SBRT is a feasible and well-tolerated approach for small neuroendocrine pancreatic tumors, demonstrating effective local control. Further investigations are vital for validation and extension of these findings.

Pancreatic Vasoactive Intestinal Peptide-Producing Tumor as a Rare Cause of Acute Diarrhea and Severe Hypokalemia

Pancreatic vasoactive intestinal peptide-producing tumor (VIPoma) is a rare functional neuroendocrine tumor most commonly presenting with watery diarrhea and electrolyte abnormalities that include hypokalemia, hypercalcemia and metabolic acidosis. This type of tumor has usually insidious clinical behavior that is characterized by chronic secretory diarrhea, lasting usually from months to years before diagnosis, not responsive to usual medical or dietary treatment approaches. Given the resemblance of VIPoma with other more common causes of chronic watery diarrhea, the final diagnosis is often delayed and the tumors are usually large and metastatic at the time of detection. Our case of pancreatic VIPoma demonstrates an unusual clinical course for this type of tumor with acute refractory diarrhea and rapid deterioration of patient's clinical and biochemical status that required emergent in-hospital diagnosis and treatment. Our patient is a 45-year-old woman who presented with abrupt, watery diarrhea during the past 24 h before admission accompanied with severe hypokalemia as well as hyponatremia, hyperglycemia and hypercalcemia. Despite aggressive management with fluid administration and electrolyte replenishment, no significant improvement in patient's symptoms and electrolyte imbalance was observed. After exclusion of other causes of acute diarrhea from the medical history and the laboratory tests, the clinical suspicion of a functional neuroendocrine tumor was raised. After the establishment of final diagnosis of pancreatic VIPoma with biochemical tests and magnetic resonance imaging (MRI), somatostatin analogues were prescribed and the patient underwent distal pancreatectomy and splenectomy with no signs of lymph node and splenic metastases. Few days after the surgical resection of the tumor, the patient readmitted to our hospital with tarry stools and severe anemia. The abdominal computed tomography (CT) revealed a retroperitoneal cystic lesion. The gastrointestinal bleeding gradually recessed after endoscopic hemostasis of duodenal ulcer lesions whereas the cystic lesion (postoperative lymphocele) was successfully drained under CT-guidance before discharge. After almost 10 years postoperatively, the patient is still asymptomatic with no signs of relapse or metastasis of the disease in the periodic laboratory and imaging follow-up. In conclusion, pancreatic VIPoma can sometimes manifest symptoms of abrupt onset and rapid progression that require high clinical suspicion, appropriate diagnostic workup and aggressive management.

Approaching Small Neuroendocrine Tumors with Radiofrequency Ablation

In recent years, small pancreatic neuroendocrine tumors (pNETs) have shown a dramatic increase in terms of incidence and prevalence, and endoscopic ultrasound (EUS) radiofrequency ablation (RFA) is one potential method to treat the disease in selected patients. As well as the heterogeneity of pNET histology, the studies reported in the literature on EUS-RFA procedures for pNETs are heterogeneous in terms of ablation settings (particularly ablation powers), radiological controls, and radiological indications. The aim of this review is to report the current reported experience in EUS-RFA of small pNETs to help formulate the procedure indications and ablation settings. Another aim is to evaluate the timing and the modality of the radiological surveillance after the ablation. Moreover, new studies on large-scale series are needed in terms of the safety and long-term oncological efficacy of RFA on these small lesions.

Metastatic pancreatic neuroendocrine tumors feature elevated T cell infiltration

Pancreatic neuroendocrine tumors (PNETs) are malignancies arising from the islets of Langerhans. Therapeutic options are limited for the over 50% of patients who present with metastatic disease. We aimed to identify mechanisms to remodel the PNET tumor microenvironment (TME) to ultimately enhance susceptibility to immunotherapy. The TMEs of localized and metastatic PNETs were investigated using an approach that combines RNA-Seq, cancer and T cell profiling, and pharmacologic perturbations. RNA-Seq analysis indicated that the primary tumors of metastatic PNETs showed significant activation of inflammatory and immune-related pathways. We determined that metastatic PNETs featured increased numbers of tumor-infiltrating T cells compared with localized tumors. T cells isolated from both localized and metastatic PNETs showed evidence of recruitment and antigen-dependent activation, suggestive of an immune-permissive microenvironment. A computational analysis suggested that vorinostat, a histone deacetylase inhibitor, may perturb the transcriptomic signature of metastatic PNETs. Treatment of PNET cell lines with vorinostat increased chemokine CCR5 expression by NF-κB activation. Vorinostat treatment of patient-derived metastatic PNET tissues augmented recruitment of autologous T cells, and this augmentation was substantiated in a mouse model of PNET. Pharmacologic induction of chemokine expression may represent a promising approach for enhancing the immunogenicity of metastatic PNET TMEs.

Development and Validation of a Modified Eighth AJCC Staging System for Primary Pancreatic Neuroendocrine Tumors

OBJECTIVE

To improve the prognostic accuracy of the eighth edition of AJCC staging system for pNETs with establishment and validation of a new staging system.

BACKGROUND

Validation of the updated eighth AJCC staging system for pNETs has been limited and controversial.

METHODS

Data from the SEER registry (1975-2016) (n = 3303) and a multi-institutional database (2000-2016) (n = 825) was used as development and validation cohorts, respectively. A mTNM was proposed by maintaining the eighth AJCC T and M definitions, and the recently proposed N status as N0 (no LNM), N1 (1-3 LNM), and N2 (≥4 LNM), but adopting a new stage classification.

RESULTS

The eighth TNM staging system failed to stratify patients with stage I versus IIA, stage IIB versus IIIA, and overall stage I versus II relative to long-term OS in both database. There was a monotonic decrement in survival based on the proposed mTNM staging classification among patients derived from both the SEER (5-year OS, stage I 87.0% vs stage II 80.3% vs stage III 72.9% vs stage IV 57.2%, all P < 0.001), and multi-institutional (5-year OS, stage I 97.6% vs stage II 82.7% vs stage III 78.4% vs stage IV 50.0%, all P < 0.05) datasets. On multivariable analysis, mTNM staging remained strongly associated with prognosis, as the hazard of death incrementally increased with each stage among patients in the 2 cohorts.

CONCLUSION

A mTNM pNETs clinical staging system using N0, N1, N2 nodal categories was better at stratifying patients relative to long-term OS than the eighth AJCC staging.

Genetically Determined Telomere Length Is Associated with Pancreatic Neuroendocrine Neoplasms Onset

INTRODUCTION

Telomere length (TL) is a potential indicator of cancer predisposition; however, the multitude of techniques used to measure it causes the results to be heterogeneous and, in some cases, controversial. In the last years, several studies adopted a strategy based on TL-associated genetic variants to generate a polygenic score, often referred as teloscore, used in lieu of direct TL measurement. For pancreatic neuroendocrine neoplasms (PanNEN), this strategy has not been attempted yet.

METHODS

A teloscore was generated using 11 SNPs (NAF1-rs7675998, ZNF676-rs409627, TERC-rs10936599, CTC1-rs3027234, PXK-rs6772228, DHX35-rs6028466, OBFC1-rs9420907, ZNF208-rs8105767, ACYP2-rs11125529, TERT-rs2736100, and ZBTB46-rs755017), and 291 PanNEN cases and 1,686 controls collected by the PANcreatic Disease ReseArch (PANDoRA) consortium were genotyped to analyse the association of the teloscore and its individual SNPs with the risk of developing PanNEN.

RESULTS

An association between genetically determined long telomeres and the risk of developing PanNEN (OR = 1.99, CI: 1.33-2.98, p = 0.0008) for highest versus median (third) quintile was observed. In addition, two novel SNPs associated with PanNEN risk were identified: ZNF676-rs409627 (ORC/C_vs_G/G = 2.27, CI: 1.58-3.27, p = 8.80 × 10-6) and TERT-rs2736100 (ORC/A_vs_C/C = 2.03, CI: 1.42-2.91, p = 1.06 × 10-4).

CONCLUSION

In conclusion, this study provides for the first time a clear indication of the association between long genetically determined telomeres and increased risk of developing PanNEN.

Enhanced computed tomography features predict pancreatic neuroendocrine neoplasm with Ki-67 index less than 5

BACKGROUND

Several studies have suggested that patients with pancreatic neuroendocrine neoplasm (pNEN) with the Ki-67 index of < 5% are more likely to show better prognosis after clinical intervention. Moreover, the Ki-67 index at 5% has also been suggested as a potential threshold by the 2016 European Neuroendocrine Tumor Society guidelines.

OBJECTIVE

Based on preoperative enhanced computed tomography (CT), this study aimed to investigate imaging characteristics eligible to discriminate the ≤ 5% Ki-67 group from the > 5% Ki-67 group of patients with nonmetastatic pNEN.

METHODS

Patients with pathologically diagnosed pNEN and preoperative multiphase CT were enrolled. Their Ki-67 index was calculated and grouped according to the 5% cutoff value. The following CT imaging characteristics and some serum biomarkers were assessed between the two groups: the diameter, location, tumor margin, calcification, pancreatic atrophy, distal pancreatic duct dilation, vessel involvement, and enhancement pattern characteristics of both arterial phase (AP) and portal vein phase (PVP).

RESULTS

A total of 142 patients with pNEN were enrolled in this study, comprising 104 in the low (Ki-67, 1%-5%) and 38 in the high index group (Ki-67, >5%). Alpha fetoprotein and cancer antigen 125 were significantly different between the two groups (P-values, 0.030 and 0.049, respectively). The diameter (P < 0.0001), margin (P = 0.003), distal main ductal dilation (P = 0.021), vessel involvement (P = 0.002), AP hypoenhancement (P < 0.0001), PVP hypoenhancement (P = 0.003), AP ratio (P = 0.0001), and PVP ratio (P = 0.0003) were significantly different between the low and high index groups. The area under the curve of the multivariate logistic regression model was 0.853.

CONCLUSION

Nonmetastatic pNENs with larger diameter, ill-defined margin, distal main ductal dilation, and tumor hypoenhancement in AP in preoperative enhanced CT tend to have a Ki-67 index of > 5%.The results of this study provide an alternative method to clinicians to decide whether surgery is appropriate.

Cancer Cells Retrace a Stepwise Differentiation Program during Malignant Progression

Pancreatic neuroendocrine tumors (PanNET) comprise two molecular subtypes, relatively benign islet tumors (IT) and invasive, metastasis-like primary (MLP) tumors. Until now, the origin of aggressive MLP tumors has been obscure. Herein, using multi-omics approaches, we revealed that MLP tumors arise from IT via dedifferentiation following a reverse trajectory along the developmental pathway of islet β cells, which results in the acquisition of a progenitor-like molecular phenotype. Functionally, the miR-181cd cluster induces the IT-to-MLP transition by suppressing expression of the Meis2 transcription factor, leading to upregulation of a developmental transcription factor, Hmgb3. Notably, the IT-to-MLP transition constitutes a distinct step of tumorigenesis and is separable from the classic proliferation-associated hallmark, temporally preceding accelerated proliferation of cancer cells. Furthermore, patients with PanNET with elevated HMGB3 expression and an MLP transcriptional signature are associated with higher-grade tumors and worse survival. Overall, our results unveil a new mechanism that modulates cancer cell plasticity to enable malignant progression. SIGNIFICANCE: Dedifferentiation has long been observed as a histopathologic characteristic of many cancers, albeit inseparable from concurrent increases in cell proliferation. Herein, we demonstrate that dedifferentiation is a mechanistically and temporally separable step in the multistage tumorigenesis of pancreatic islet cells, retracing the developmental lineage of islet β cells.This article is highlighted in the In This Issue feature, p. 2355.

Pancreatic Neuroendocrine Neoplasms: CT Spectral Imaging in Grading

RATIONALE AND OBJECTIVES

The purpose of this study was to define the CT spectral imaging characteristics of pancreatic neuroendocrine neoplasms (PNENs) and evaluate their potential for differential diagnosis of nonlow grade (non-LG) PNENs from low grade (LG) PNENs.

MATERIALS AND METHODS

CT spectral imaging data of 54 pathologically proven PNENs were retrospectively reviewed. Patients were divided into two groups: 40 cases with grade 1 in LG PNENs group and 14 cases with grade 2 and grade 3 in non-LG PNENs group.

RESULTS

Gender, calcification, inhomogeneity, invasiveness, PD dilatation, lymph node enlargement, size, normalized iodine (water) concentration in arterial phase (AP) (Iodine (ap)), normalized effective-Z (Z_ap), slope of normalized CT spectral curves in both AP, and portal venous phase were found to be significant variables for differentiating non-LG PNENs from LG PNENs (p < 0.05). Non-LG PNENs had larger size and lower Z_ap and Iodine (ap) than LG PNENs. The tumor size, Z_ap and Iodine (ap) had fair to good diagnostic performance with the area under receiver-operating-characteristic curve (AUC) 0.843, 0.733, and 0.728, respectively. Multivariate analysis with logistic regression had higher AUC (p<0.05) than all the single parameters except for size.

CONCLUSION

There were significant differences in CT spectral imaging parameters between non-LG and LG PNENs. Tumor size was the most promising independent parameter and the combination of quantitative parameters with qualitative parameters is the best predictor in differentiating of non-LG PNENs from LG PNENs. CT spectral imaging can help determine the malignancy of PNENs, which can better assist in surgical planning.

SST gene hypermethylation acts as a pan-cancer marker for pancreatic ductal adenocarcinoma and multiple other tumors: toward its use for blood-based diagnosis

Aberrant DNA methylation is often involved in carcinogenesis. Our initial goal was to identify DNA methylation biomarkers associated with pancreatic cancer. A genomewide methylation study was performed on DNA from pancreatic ductal adenocarcinoma (PDAC) and endocrine pancreas tumors. Validation of DNA methylation patterns and concomitant alterations in expression of gene candidates was performed on patient samples and pancreatic cancer cell lines. Furthermore, validation was done on independent data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO). Finally, droplet digital PCR was employed to detect DNA methylation marks in cell-free (cf) DNA isolated from plasma samples of PDAC patients and cancer-free blood donors. Hypermethylation of the SST gene (encoding somatostatin) and concomitant downregulation of its expression were discovered in PDAC and endocrine tumor tissues while not being present in chronic pancreatitis (inflamed) tissues and normal pancreas. Fittingly, treatment with a somatostatin agonist (octreotide) reduced cell proliferation and migration of pancreatic cancer cells. Diagnostic performance of SST methylation in a receiver operating characteristic curve analysis was 100% and 89% for tissue and plasma samples, respectively. A large body of TCGA and GEO data confirmed SST hypermethylation and downregulation in PDAC and showed a similar effect in a broad spectrum of other tumor entities. SST promoter methylation represents a sensitive and promising molecular, pan-cancer biomarker detectable in tumor tissue, and liquid biopsy samples.

CT radiomics may predict the grade of pancreatic neuroendocrine tumors: a multicenter study

OBJECTIVE

To develop and validate a radiomics-based nomogram for preoperatively predicting grade 1 and grade 2/3 tumors in patients with pancreatic neuroendocrine tumors (PNETs).

METHODS

One hundred thirty-eight patients derived from two institutions with pathologically confirmed PNETs (104 in the training cohort and 34 in the validation cohort) were included in this retrospective study. A total of 853 radiomic features were extracted from arterial and portal venous phase CT images respectively. Minimum redundancy maximum relevance and random forest methods were adopted for the significant radiomic feature selection and radiomic signature construction. A fusion radiomic signature was generated by combining both the single-phase signatures. The nomogram based on a comprehensive model incorporating the clinical risk factors and the fusion radiomic signature was established, and decision curve analysis was applied for clinical use.

RESULTS

The fusion radiomic signature has significant association with histologic grade (p < 0.001). The nomogram integrating independent clinical risk factor tumor margin and fusion radiomic signature showed strong discrimination with an area under the curve (AUC) of 0.974 (95% CI 0.950-0.998) in the training cohort and 0.902 (95% CI 0.798-1.000) in the validation cohort with good calibration. Decision curve analysis verified the clinical usefulness of the predictive nomogram.

CONCLUSION

We proposed a comprehensive nomogram consisting of tumor margin and fusion radiomic signature as a powerful tool to predict grade 1 and grade 2/3 PNET preoperatively and assist the clinical decision-making for PNET patients.

KEY POINTS

• Radiomic signature has strong discriminatory ability for the histologic grade of PNETs. • Arterial and portal venous phase CT imaging are complementary for the prediction of PNET grading. • The comprehensive nomogram outperformed clinical factors in assisting therapy strategy in PNET patients.

Pancreatic neuroendocrine tumor: prediction of the tumor grade using magnetic resonance imaging findings and texture analysis with 3-T magnetic resonance

Purpose

The purpose of this study was to evaluate the performance of magnetic resonance imaging (MRI) findings and texture parameters for prediction of the histopathologic grade of pancreatic neuroendocrine tumors (PNETs) with 3-T magnetic resonance.

Patients and methods

PNETs are classified into Grade 1 (G1), Grade 2 (G2), and Grade 3 (G3) tumors based on the Ki-67 proliferation index and the mitotic activity. A total of 77 patients with pathologically confirmed PNETs met the inclusion criteria. Texture analysis (TA) was applied to T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI) maps. Patient demographics, MRI findings, and texture parameters were compared among three different histopathologic subtypes by using Fisher’s exact tests or Kruskal–Wallis test. Then, logistic regression analysis was adopted to predict tumor grades. ROC curves and AUCs were calculated to assess the diagnostic performance of MRI findings and texture parameters in prediction of tumor grades.

Results

There were 31 G1, 29 G2, and 17 G3 patients. Compared with G1, G2/G3 tumors showed higher frequencies of an ill-defined margin, a predominantly solid tumor type, local invasion or metastases, hypo-enhancement at the arterial phase, and restriction diffusion. Four T2-based (inverse difference moment, energy, correlation, and differenceEntropy) and five DWI-based (correlation, contrast, inverse difference moment, maxintensity, and entropy) TA parameters exhibited statistical significance among PNETs (P<0.001). The AUCs of six predicting models on T2WI and DWI ranged from 0.703–0.989.

Conclusion

Our data indicate that MRI findings, including tumor margin, texture, local invasion or metastases, tumor enhancement, and diffusion restriction, as well as texture parameters can aid the prediction of PNETs grading.

Strong antitumor efficacy of a pancreatic tumor-targeting oncolytic adenovirus for neuroendocrine tumors

Although oncolytic adenoviruses are promising cancer therapy agents, for effective oncolytic activity, viruses need to specifically infect and effectively replicate in cancer cells but not in normal cells. We have previously identified a pancreatic cancer-targeting ligand, SYENFSA (SYE), by screening an adenovirus library displaying random peptides against human pancreatic cancer cells and reported that a survivin promoter-regulated adenovirus, displaying the SYE ligand (AdSur-SYE), provided effective oncolysis of pancreatic ductal adenocarcinoma (PDAC) in a preclinical study. As we examined the infectivity of AdSur-SYE in human surgical specimens of various pancreatic tumors, we unexpectedly found that AdSur-SYE showed high gene transduction efficiency for pancreatic neuroendocrine tumors (PNETs) as well as for PDAC, 9.1- and 6.2-fold, respectively, compared to that of the nontargeting virus (AdSur). The infectivity of both vectors was almost the same in other cancers and organs such as the pancreas. Immunostaining indicated that the cells infected with AdSur-SYE were PNET cells but not stromal cells. AdSur-SYE showed a significantly higher oncolytic potency than that of AdSur in human PNET cell lines, and intratumoral infection with AdSur-SYE completely diminished subcutaneous tumors in a murine model, in which AdSur-SYE effectively proliferated and spread. AdSur-SYE exerted a stronger oncolytic effect in primary PNET cells cocultured with mouse embryonic fibroblasts than AdSur did. Thus, AdSur-SYE shows promise as a next-generation therapy for PNET.

Pancreatic neuroendocrine neoplasms: Correlation between MR features and pathological tumor grades

This study investigated the accuracy of MRI features in differentiating the pathological grades of pancreatic neuroendocrine neoplasms (PNENs). A total of 31 PNENs patients were retrospectively evaluated, including 19 cases in grade 1, 5 in grade 2, and 7 in grade 3. Plain and contrastenhanced MRI was performed on all patients. MRI features including tumor size, margin, signal intensity, enhancement patterns, degenerative changes, duct dilatation and metastasis were analyzed. Chi square tests, Fisher's exact tests, one-way ANOVA and ROC analysis were conducted to assess the associations between MRI features and different tumor grades. It was found that patients with older age, tumors with higher TNM stage and without hormonal syndrome had higher grade of PNETs (all P<0.05). Tumor size, shape, margin and growth pattern, tumor pattern, pancreatic and bile duct dilatation and presence of lymphatic and distant metastasis as well as MR enhancement pattern and tumor-topancreas contrast during arterial phase were the key features differentiating tumors of all grades (all P<0.05). ROC analysis revealed that the tumor size with threshold of 2.8 cm, irregular shape, pancreatic duct dilatation and lymphadenopathy showed satisfactory sensitivity and specificity in distinguishing grade 3 from grade 1 and grade 2 tumors. Features of peripancreatic tissue or vascular invasion, and distant metastasis showed high specificity but relatively low sensitivity. In conclusion, larger size, poorlydefined margin, heterogeneous enhanced pattern during arterial phase, duct dilatation and the presence of metastases are common features of higher grade PNENs. Plain and contrast-enhanced MRI provides the ability to differentiate tumors with different pathological grades.

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.

p53 and p16Ink4a/p19Arf Loss Promotes Different Pancreatic Tumor Types from PyMT-Expressing Progenitor Cells

In human studies and mouse models, the contributions of p53 and p16^Ink4a/p19^Arf loss are well established in pancreatic ductal adenocarcinoma (PDAC). Although loss of functional p53 pathway and loss of Ink4a/Arf in human pancreatic acinar cell carcinoma (PACC) and pancreatic neuroendocrine tumor (PanNET) are identified, their direct roles in tumorigenesis of PACC and PanNET remain to be determined. Using transgenic mouse models expressing the viral oncogene polyoma middle T antigen (PyMT), we demonstrate that p53 loss in pancreatic Pdx1+ progenitor cells results in aggressive PACC, whereas Ink4a/Arf loss results in PanNETs. Concurrent loss of p53 and Ink4a/Arf resembles loss of p53 alone, suggesting that Ink4a/Arf loss has no additive effect to PACC progression. Our results show that specific tumor suppressor genotypes provocatively influence the tumor biological phenotypes in pancreatic progenitor cells. Additionally, in a mouse model of β-cell hyperplasia, we demonstrate that p53 and Ink4a/Arf play cooperative roles in constraining the progression of PanNETs.

Pancreatic neuroendocrine tumors: correlation between histogram analysis of apparent diffusion coefficient maps and tumor grade

PURPOSE

To explore the role of histogram analysis of apparent diffusion coefficient (ADC) MRI maps based on entire tumor volume data in determining pancreatic neuroendocrine tumor (PNT) grade.

METHODS AND MATERIALS

Retrospective evaluation of 22 patients with PNTs included low-grade (G1; n = 15), intermediate-grade (G2; n = 4), and high-grade (G3; n = 3) tumors. Regions of interest containing the lesion were drawn on every section of the ADC map containing the tumor and summated to obtain histograms for entire tumor volume. Calculated histographic parameters included mean ADC (mADC), 5th percentile ADC, 10th percentile ADC, 25th percentile ADC, 50th percentile ADC, 75th percentile ADC (ADC75), 90th percentile ADC (ADC90) and 95th percentile ADC (ADC95), skewness and kurtosis. Histogram parameters were correlated with tumor grade by repeated measures analysis of variance with Tukey-Kramer post hoc comparisons.

RESULTS

The mADC, ADC75, ADC90, and ADC95 were significantly higher in G1 tumors (1283 ± 267; 1404 ± 300; 1495 ± 318; 1562 ± 347 × 10(-6) mm(2)/s) compared to G2 (892 ± 390; 952 ± 381; 1036 ± 384; 1072 ± 374 × 10(-6) mm(2)/s) and to G3 tumors (733 ± 225; 864 ± 284; 1008 ± 288; 1152 ± 192 × 10(-6) mm(2)/s) (p value <0.05). Skewness and kurtosis were significantly different between G1 (0.041 ± 0.466; 2.802 ± 0.679) and G3 (1.01 ± 1.140; 5.963 ± 4.008) tumors (p value <0.05). Tumor volume (mL) was significantly higher on G3 (55 ± 15.7) compared to G1 (1.9 ± 2.7) and G2 (4.5 ± 3.6) tumors (p value <0.05). In this small sample size, we did not detect statistically significant parameters between G2 (n = 4) and G3 (n = 3) tumors.

CONCLUSIONS

Histographic analysis of ADC maps on the basis of the entire tumor volume can be useful in differentiating histologic grades of PNTs.

Behavior of Small, Asymptomatic, Nonfunctioning Pancreatic Neuroendocrine Tumors (NF-PNETs)

Small nonfunctioning pancreatic neuroendocrine tumors (NF-PNETs) usually exhibit minimal or no growth over many years. However, there is a controversy regarding the optimal management of incidentally discovered, small NF-PNETs. This study aimed to gain insights into tumor behavior and potential strategies for clinical management.We retrospectively reviewed a total of 202 patients with a suspected PNET (size 2 cm or smaller) at Samsung Medical Center from January 1, 1995 to April 30, 2012. Among these patients, 72 patients were excluded and 145 patients were enrolled in our study. Patients were included if the size of the tumor was ≤2 cm without familial syndrome, radiographic evidence of local invasion or metastases.Among the 145 patients, 76 patients (52.4%) had pathologically confirmed PNETs. Eleven (14.5%) and 3 (3.9%) of these 76 patients were diagnosed with NET G2 and G3, respectively. PNETs measuring 1.5 cm or more in size had a higher probability of being classified as NET G2 or G3 compared with PNETs measuring <1.5 cm (P = 0.03). Older age (≥55 years) and a meaningful tumor growth (≥20% or ≥5 mm) were significantly associated with NET G2 or G3 (P < 0.05).Older age (≥55 years), larger tumor size (≥1.5 cm), and a meaningful tumor growth (≥20% or ≥5 mm) were associated with NET G2 or G3. Intensive follow-up could be an acceptable approach in small (especially <1.5 cm), asymptomatic, NF-PNETs.

Intravoxel incoherent motion diffusion-weighted imaging of pancreatic neuroendocrine tumors: prediction of the histologic grade using pure diffusion coefficient and tumor size

PURPOSE

The purpose of this study was to assess the value of intravoxel incoherent motion and diffusion-weighted imaging for predicting the histologic grade of pancreatic neuroendocrine tumors (PNETs).

MATERIALS AND METHODS

Forty patients with surgically diagnosed PNETs who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging with a series of 10 b values (0-1000 s/mm(2), were included in this institutional review board-approved retrospective study. The apparent diffusion coefficient (ADC(total)), the intravoxel incoherent motion parameters (pure diffusion coefficient [D], pseudodiffusion coefficient [D(*)], and perfusion fraction [f]) were measured on the tumors. Histologic grading was performed on the basis of the World Health Organization 2010 classification system. Logistic regression analysis and receiver operating curve analysis were performed to identify the significant factors predicting the histologic grades.

RESULTS

Grades 2 and 3 tumors were significantly larger than grade 1 tumors (average 3.62 cm vs 2.17 cm in diameter; P=0.001). Grades 2 and 3 tumors showed significantly lower D values than did grade 1 tumors (0.95 vs 1.21×10(-3) mm(2)/s; P=0.009), although the ADC(total) showed no significant difference. When any of the following 2 criteria was used, (a) tumor size smaller than 2.0 cm in diameter and (b) D value greater than 1.2×10(-3) mm(2)/s, the sensitivity, specificity, and positive predictive value for diagnosing grade 1 PNETs were 76.92%, 100%, and 100%, respectively.

CONCLUSIONS

Pure diffusion coefficient (D) is possibly a better marker than ADC(total) is for differentiating grade 1 from grade 2 or 3 PNET and, combined with tumor size, can predict grade 1 PNET with a high specificity.

Advancements in pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PanNETs) have increased in incidence in the USA over the last 20 years. Although PanNETs are often misconceived as being indolent tumors as they have a far more favorable prognosis over pancreatic adenocarcinoma, roughly 60-70% of patients have metastatic disease at the time of diagnosis due to presentation late in the disease process. While improvements in imaging modalities allow for early detection and better tumor localization, recent advancements in basic science, as well as surgical and medical management of PanNETs have further improved the prognosis. The mainstay of therapy for localized PanNETs is surgical intervention, which has become safer and is slowly shifting towards a more minimally invasive approach. However, the prognosis still remains relatively bleak for patients with unresectable disease. Fortunately, novel molecular targeted therapies, such as everolimus and sunitinib, have recently come into the limelight and have shown significant promise for the treatment of locally advanced and metastatic disease.

Synthesis, Structural Characterisation, and Preliminary Evaluation of Non-Indolin-2-one-based Angiogenesis Inhibitors Related to Sunitinib (Sutent®)

The indolin-2-one fused-ring system and the 2,4-dimethylpyrrole unit represent key structural motifs in the anticancer drug sunitinib (Sutent®) and predecessor angiogenesis inhibitors that have undergone anticancer clinical trials (e.g. semaxanib, SU5416). In pursuit of novel anti-angiogenic scaffolds, we were interested in identifying whether the indolin-2-one group in these structures could be modified without losing activity. This paper describes novel condensation chemistry used to prepare a test series of (E)- and (Z)-alkenes related to SU5416 that retain the 2,4-dimethylpyrrole unit while incorporating ring-opened indolin-2-ones. Unique structural characteristics were identified in the compounds, such as intramolecular hydrogen bonds in the (Z)-alkenes, and several examples were shown to possess significant anti-angiogenic activity in a rat aorta in vitro model of angiogenesis. The work demonstrates that the indolin-2-one moiety is not an absolute requirement for angiogenesis inhibition in the sunitinib/SU5416 class.

Pathology - grading and staging of GEP-NETs

Gastroenteropancreatic neuroendocrine tumours (GEP-NETs) constitute a heterogeneous group of neoplasms. In the last few decades, due to a substantial rise in incidence and prevalence, GEP-NETs have been included among the most common tumours of the gastrointestinal tract. Diagnosis could be challenging and a significant number of patients present with metastatic or unresectable disease. The development of appropriate tools for standardised prognostic stratification and the introduction of effective target therapies have opened new horizons for planning tailored surgical or medical management and follow-up programs for these complex neoplasms. An overview on the GEP-NETs' diagnostic and prognostic criteria proposed by the recently published WHO classification and ENETS and UICC TNM staging systems is presented, focussing on their impact on the clinical and therapeutical approaches.