Management of Pancreatic Neuroendocrine Tumors: Surgical Strategies and Controversies

OBJECTIVE

Pancreatic neuroendocrine tumors (PNETs) are uncommon tumors which are increasing in incidence. The management of these tumors continues to evolve. This review examines the current role of surgery in the treatment of these tumors.

METHODS

Studies published over the past 10 years were identified using several databases including PubMed, MEDLINE, and Science Direct. Search terms included PNETs, treatment, and surgery. Clinical practice guidelines and updates from several major groups were reviewed.

RESULTS

Surgery continues to have a major role in the treatment of sporadic functional and nonfunctional PNETs. Pancreas-sparing approaches are increasingly accepted as alternatives to formal pancreatic resection in selected patients. Options such as watch and wait or endoscopic ablation may be reasonable alternatives to surgery for non-functional PNETs < 2 cm in size. Surgical decision-making in multiple endocrine neoplasia type 1 patients remains complex and in some situations such as gastrinoma quite controversial. The role of surgery has significantly diminished in patients with advanced disease due to the advent of more effective systemic and liver-directed therapies. However, the optimal treatments and sequencing in advanced disease remain poorly defined, and it has been suggested that surgery is underutilized in these patients.

CONCLUSIONS

Surgery remains a major treatment modality for PNETs. Given the plethora of available treatments, ongoing controversies and the changing landscape, management has become increasingly complex. An experienced multidisciplinary team which includes surgery is essential to manage these patients.

Differentiating small (< 2 cm) pancreatic ductal adenocarcinoma from neuroendocrine tumors with multiparametric MRI-based radiomic features

OBJECTIVES

To assess MR-based radiomic analysis in preoperatively discriminating small (< 2 cm) pancreatic ductal adenocarcinomas (PDACs) from neuroendocrine tumors (PNETs).

METHODS

A total of 197 patients (146 in the training cohort, 51 in the validation cohort) from two centers were retrospectively collected. A total of 7338 radiomics features were extracted from T2-weighted, diffusion-weighted, T1-weighted, arterial phase, portal venous phase and delayed phase imaging. The optimal features were selected by the Mann-Whitney U test, Spearman's rank correlation test and least absolute shrinkage and selection operator method and used to construct the radiomic score (Rad-score). Conventional radiological and clinical features were also assessed. Multivariable logistic regression was used to construct a radiological model, a radiomic model and a fusion model.

RESULTS

Nine optimal features were identified and used to build the Rad-score. The radiomic model based on the Rad-score achieved satisfactory results with AUCs of 0.905 and 0.930, sensitivities of 0.780 and 0.800, specificities of 0.906 and 0.952 and accuracies of 0.836 and 0.863 for the training and validation cohorts, respectively. The fusion model, incorporating CA19-9, tumor margins, pancreatic duct dilatation and the Rad-score, exhibited the best performance with AUCs of 0.977 and 0.941, sensitivities of 0.914 and 0.852, specificities of 0.954 and 0.950, and accuracies of 0.932 and 0.894 for the training and validation cohorts, respectively.

CONCLUSIONS

The MR-based Rad-score is a novel image biomarker for discriminating small PDACs from PNETs. A fusion model combining radiomic, radiological and clinical features performed very well in differentially diagnosing these two tumors.

CLINICAL RELEVANCE STATEMENT

A fusion model combining MR-based radiomic, radiological, and clinical features could help differentiate between small pancreatic ductal adenocarcinomas and pancreatic neuroendocrine tumors.

KEY POINTS

Preoperatively differentiating small pancreatic ductal adenocarcinomas (PDACs) and pancreatic neuroendocrine tumors (PNETs) is challenging. Multiparametric MRI-based Rad-score can be used for discriminating small PDACs from PNETs. A fusion model incorporating radiomic, radiological, and clinical features differentiated small PDACs from PNETs well.

Optimal surgical management of unifocal vs. multifocal NF-PNETs: a respective cohort study

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) represent 1-2% of pancreatic tumors, with recent guidelines recommending active surveillance for non-functioning PNETs (NF-PNETs) smaller than 2 cm. However, the management of multiple NF-PNETs, as well as the influence of tumor number on prognosis, remains under-researched.

METHODS

This retrospective study analyzed NF-PNET patients who underwent pancreatic resection at Severance Hospital between February 1993 and August 2023, comparing the characteristics of patients diagnosed with multifocal tumors and those with unifocal tumors. A subgroup analysis of overall survival (OS) and recurrence-free survival (RFS) was performed based on multifocality employing the Kaplan-Meier method and the log-rank test.

RESULTS

Of 187 patients, 169 (90.4%) had unifocal and 18 (9.6%) had multifocal tumors. Multifocal tumors were more likely to be diffusely spread, necessitating more total pancreatectomies (diffuse tumor location: 4.7% in unifocal vs. 38.9% in multifocal cases, p < 0.001; total pancreatectomy: 4.1% in unifocal vs. 33.3% in multifocal cases, p < 0.001). In patients with NF-PNET who underwent the same extent of pancreatic resection, no significant difference in the incidence of complication was observed regardless of multifocality. Moreover, no significant difference in OS was seen between the unifocal and multifocal groups (log-rank test: p = 0.93). However, the multifocal group exhibited a poorer prognosis in terms of RFS compared to the unifocal group (log-rank test: p = 0.004) Hereditary syndrome, tumor grade, size, lymphovascular invasion, and lymph node metastasis were key factors in the recurrence.

CONCLUSION

This study's findings suggest that the presence of multiple tumors was associated with poorer recurrence-free survival but did not affect long-term survival following surgery. Given the long-term oncologic outcome and quality of life following surgery, resection of tumors over 2 cm is advisable in patients with multifocal PNETs, while a cautious "wait-and-see" approach for smaller tumors (under 2 cm) can minimize the extent of resection and improve the quality of life. In cases with only small multifocal NF-PNETs (< 2 cm), immediate resection may not be crucial, but the higher recurrence rate than that in solitary NF-PNET necessitates intensified surveillance.

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.

Long-term Follow-up of Small Nonfunctioning Pancreatic Neuroendocrine Tumors Diagnosed Using Endoscopic Ultrasound-guided Fine-needle Aspiration

Objective Clinical practice guidelines in Japan recommend surgery for all nonfunctioning pancreatic neuroendocrine tumors (NF-PNETs), regardless of their size or associated symptoms. Because pancreatic resection is highly invasive, follow-up for small NF-PNETs is often chosen in clinical practice. However, the natural history of NF-PNET remains poorly understood. We aimed to examine the natural history of pathologically confirmed NF-PNET. Methods This single-center retrospective case series investigated NF-PNETs that were pathologically diagnosed using endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) at our hospital between 2014 and 2018. Patients who were followed up without treatment due to their general condition or their wish were included in the study. Patients' background characteristics, imaging findings, pathological findings, and long-term prognoses were investigated using medical records. Results Overall, 26 patients were diagnosed with NF-PNET by EUS-FNA during the observation period. Of these, 9 patients (3 men and 6 women; median age: 64 years old) were followed up without treatment. All of these patients were asymptomatic, and localization was noticed in 3 cases in the head, body, and tail (1 each), with a median size of 12 (range: 4-18) mm. Neuroendocrine tumor (Grade 1 [G1]) was pathologically diagnosed in all patients with EUS-FNA. The median observation period was 63 (range: 26-90) months. Tumor growth and distant metastasis were not observed in any of the nine patients who remained asymptomatic. Conclusion Follow-up is a feasible option for asymptomatic NF-PNET ≤20 mm in size with a pathological grade of G1.

Development and validation of CT-based radiomics deep learning signatures to predict lymph node metastasis in non-functional pancreatic neuroendocrine tumors: a multicohort study

Background

Lymph node status is an important factor for the patients with non-functional pancreatic neuroendocrine tumors (NF-PanNETs) with respect to the surgical methods, prognosis, recurrence. Our aim is to develop and validate a combination model based on contrast-enhanced CT images to predict the lymph node metastasis (LNM) in NF-PanNETs.

Methods

Retrospective data were gathered for 320 patients with NF-PanNETs who underwent curative pancreatic resection and CT imaging at two institutions (Center 1, n = 236 and Center 2, n = 84) between January 2010 and March 2022. RDPs (Radiomics deep learning signature) were developed based on ten machine-learning techniques. These signatures were integrated with the clinicopathological factors into a nomogram for clinical applications. The evaluation of the model's performance was conducted through the metrics of the area under the curve (AUC).

Findings

The RDPs showed excellent performance in both centers with a high AUC for predicting LNM and disease-free survival (DFS) in Center 1 (AUC, 0.88; 95% CI: 0.84-0.92; DFS, p < 0.05) and Center 2 (AUC, 0.91; 95% CI: 0.85-0.97; DFS, p < 0.05). The clinical factors of vascular invasion, perineural invasion, and tumor grade were associated with LNM (p < 0.05). The combination nomogram showed better prediction capability for LNM (AUC, 0.93; 95% CI: 0.89-0.96). Notably, our model maintained a satisfactory predictive ability for tumors at the 2-cm threshold, demonstrating its effectiveness across different tumor sizes in Center 1 (≤2 cm: AUC, 0.90 and >2 cm: AUC, 0.86) and Center 2 (≤2 cm: AUC, 0.93 and >2 cm: AUC, 0.91).

Interpretation

Our RDPs may have the potential to preoperatively predict LNM in NF-PanNETs, address the insufficiency of clinical guidelines concerning the 2-cm threshold for tumor lymph node dissection, and provide precise therapeutic strategies.

Funding

This work was supported by JSPS KAKENHI Grant Number JP22K20814; the Rare Tumor Research Special Project of the National Natural Science Foundation of China (82141104) and Clinical Research Special Project of Shanghai Municipal Health Commission (202340123).

Reappraisal of Malignant Risk Assessment for Small (≤20 mm) Non-functioning Pancreatic Neuroendocrine Tumors

BACKGROUND

Optimal management of non-functioning pancreatic neuroendocrine tumors (PanNETs) ≤20 mm is controversial. The biological heterogeneity of these tumors poses challenges when deciding between resection and observation.

METHODS

In this multicenter, retrospective cohort study, we analyzed all patients (n = 78) who underwent resection of non-functioning PanNETs ≤20 mm at three tertiary medical centers from 2004 to 2020 to assess the utility of preoperatively available radiological features and serological biomarkers of non-functioning PanNETs in choosing an optimal surgical indication. The radiological features included non-hyper-attenuation pattern on enhancement computed tomography (CT; hetero/hypo-attenuation) and main pancreatic duct (MPD) involvement, and serological biomarkers included elevation of serum elastase 1 and plasma chromogranin A (CgA) levels.

RESULTS

Of all small non-functioning PanNETs, 5/78 (6%) had lymph node metastasis, 11/76 (14%) were WHO grade II, and 9/66 (14%) had microvascular invasion; 20/78 (26%) had at least one of these high-risk pathological factors. In the preoperative assessment, hetero/hypo-attenuation and MPD involvement were observed in 25/69 (36%) and 8/76 (11%), respectively. Elevated serum elastase 1 and plasma CgA levels were observed in 1/33 (3%) and 0/11 (0%) patients, respectively. On multivariate logistic regression analysis, hetero/hypo-attenuation (odds ratio [OR] 6.1, 95% confidence interval [CI] 1.7-22.2) and MPD involvement (OR 16.8, 95% CI 1.6-174.3) were significantly associated with the high-risk pathological factors. The combination of the two radiological worrisome features correctly predicted non-functioning PanNETs with high-risk pathological factors, with about 75% sensitivity, 79% specificity, and 78% accuracy.

CONCLUSIONS

This combination of radiological worrisome features can accurately predict non-functioning PanNETs that may require resection.

Small nonfunctional pancreatic neuroendocrine neoplasms: Time for a step-up treatment approach?

Surgery has been regarded as the only curative treatment for patients with small nonfunctional pancreatic neuroendocrine neoplasms (NF-PNENs) less than 2 cm. Due to the significant adverse event rates of surgery, the European Neuroendocrine Tumor Society issued guidelines favoring surveillance for those patients lacking criteria suggestive of an aggressive disease. Despite the above recommendations, a significant proportion of small NF-PNEN patients still undergo surgery. Recently, several studies have reported the safety and effectiveness of EUS-guided radiofrequency ablation (RFA) for the treatment of small NF-PNENs. The experience with EUS-RFA is, however, limited, but published results indicate a potential role as a minimally invasive alternative treatment for these patients, in particular in those in whom further progression is more probable, before they reach the absolute need for surgery. A step-up approach with EUS-RFA followed by surgery for the failure cases can become a valid option to be validated in clinical studies.

Characteristics of small pancreatic neuroendocrine tumors and risk factors for invasion and metastasis

BACKGROUND

The number of people with small pancreatic neuroendocrine tumors (pNETs) (tumors with a diameter less than or equal to 2 cm) is gradually increasing, but the selection of treatment strategy is still controversial. Our aim was to characterize small pNETs with a poor prognosis and to define the impact of aggressive small pNETs on survival and the risk factors for the development of invasive disease.

METHODS

Patients with pNETs diagnosed between 2004 and 2019 and a tumor diameter of 2 cm or less were selected from the SEER Registry. Kaplan-Meier survival analysis was used to identify the factors affecting patient survival, and binary logistic regression was used to identify the associated risk factors.

RESULTS

A total of 3261 patients with pNETs were enrolled in the study. Both older and younger patients benefited from surgery. Regional invasion occurred in 10% of the patients, and distant metastases occurred in 9% of the patients, but in both categories, those who underwent surgery had better survival outcomes than those who did not. There was no difference in survival between patients with a tumor diameter of 1-2 cm and those with a tumor diameter of less than 1 cm, and there was no difference in survival between patients with functional and nonfunctional small pNETs. However, the survival of patients with pNETs in the head of the pancreas was worse than that of patients with tumors in other parts of the pancreas. Survival was worse in elderly patients and in those with poorly differentiated and undifferentiated tumors. Lymphatic metastasis, regional invasion, and distant metastasis all worsened the prognosis of patients. The presence or absence of neuroendocrine function, the degree of tumor differentiation, and the location of the tumor were associated with the risk of lymphatic metastasis and regional invasion; the risk factors for distant metastasis were associated with the degree of differentiation and tumor location.

CONCLUSION

The pNETs ≤ 2 cm in diameter could be still aggressive, and patient prognosis worsens after invasive disease develops. Attention to the characteristics of aggressive tumors can improve patient survival.

A novel tool to predict nodal metastasis in small pancreatic neuroendocrine tumors: A multicenter study

BACKGROUND

Nonfunctional pancreatic neuroendocrine tumors display a wide range of biological behavior, and nodal disease is associated with metastatic disease and poorer survival. The aim of this study was to develop a tool to predict nodal disease in patients with small (≤2 cm) nonfunctional pancreatic neuroendocrine tumors.

METHODS

A multicenter retrospective study was performed on patients undergoing resection for small nonfunctional pancreatic neuroendocrine tumors. Patients with genetic syndromes, metastatic disease at diagnosis, neoadjuvant therapy, or positive resection margin were excluded. Factors associated with nodal disease were identified to develop a predictive model. Internal validation was performed using bootstrap with 1,000 resamples.

RESULTS

Nodal disease was observed in 39 (11.1%) of the 353 patients included. Presence of nodal disease was significantly associated with lower 5-year disease-free survival (71.6% vs 96.2%, P < .001). Two predictors were strongly associated with nodal disease: G2 grade (odds ratio: 3.51, 95% confidence interval: 1.71-7.22, P = .001) and tumor size (per mm increase, odds ratio: 1.14, 95% confidence interval: 1.03-1.25, P = .009). Adequate discrimination was observed with an area under the curve of 0.71 (95% confidence interval: 0.63-0.80). Based on risk distribution, 3 risk groups of nodal disease were identified; low (<5%), intermediate (≥5% to <20%), and high (≥20%) risk. The observed mean risk of nodal disease was 3.7% in the low-risk patients, 9.6% in the intermediate-risk patients, and 30.4% in the high-risk patients (P < .001). The 10-year disease-free survival in the low, intermediate, and high-risk groups was 100%, 88.8%, and 50.1%, respectively.

CONCLUSION

Our model using tumor grade and size can predict nodal disease in small nonfunctional pancreatic neuroendocrine tumors. Integration of this tool into clinical practice could help guide management of these patients.

Survival after active surveillance versus upfront surgery for incidental small pancreatic neuroendocrine tumours

BACKGROUND

The safety of observing small non-functioning pancreatic neuroendocrine tumours (NF-Pan-NETs) remains under debate.

METHODS

This was a multicentre retrospective study of patients with small incidental NF-Pan-NETs. Survival of patients who underwent upfront surgery versus active surveillance was compared. The risk of death was matched with that in the healthy population. The excess hazard rate and probability of a normal lifespan (NLP) were calculated. Propensity score matching (PSM) with a 1 : 1 ratio was used to minimize the risk of selection bias.

RESULTS

Some 222 patients (43.7 per cent) underwent upfront surgery and 285 (56.3 per cent) were observed. The excess hazard rate for the entire cohort was quantifiable as 0.04 (95 per cent c.i. 0 to 0.08) deaths per 1000 persons per year, and the NLP was 99.7 per cent. Patients in the active surveillance group were older (median age 65 versus 58 years; P < 0.001), and more often had co-morbidity (45.3 versus 24.8 per cent; P = 0.001), and smaller tumours (median 12 versus 13 mm; P < 0.001), less frequently located in the pancreatic body-tail (59.5 versus 69.6 per cent; P = 0.008, 59.3 versus 73.9 per cent; P = 0.001). Median follow-up was longer for patients who underwent upfront surgery (5.6 versus 2.7 years; P < 0.001). After PSM, 118 patients per group were included. The excess hazard rates were 0.2 and 0.9 deaths per 1000 persons per year (P = 0.020) for patients in the active surveillance and upfront surgery groups respectively. Corresponding NLPs were 99.9 and 99.5 per cent respectively (P = 0.011).

CONCLUSION

Active surveillance of small incidental NF-Pan-NETs is a reasonable alternative to resection.

Sporadic nonfunctional pancreatic neuroendocrine tumors: Risk of lymph node metastases and aggressiveness according to tumor size: A multicenter international study

BACKGROUND

Although the correlation between tumor size and aggressiveness is clearly established in sporadic nonfunctional pancreatic neuroendocrine tumors, the management of tumors ≤2 cm remains debated. In recent guidelines, the cut-off size to operate ranged from 1 to 2 cm. The aim of this retrospective study was to report the rate of lymph nodes metastases in resected sporadic nonfunctional pancreatic neuroendocrine tumors, according to tumor size and, second, to identify risk factors of lymph node metastases and disease-free survival.

METHODS

Resected sporadic nonfunctional pancreatic neuroendocrine tumors from 9 international expert centers were included (1999-2017). Functional pancreatic neuroendocrine tumors, genetic syndromes, and R2 resection were excluded. Aggressiveness was defined as microvascular invasion, perineural invasion, lymph node metastases, G3 grading, distant metastases, and/or recurrence.

RESULTS

Overall, 495 resected sporadic nonfunctional pancreatic neuroendocrine tumors were included. For tumors up to 5 cm, the risk of lymph node metastases was increased by 1.73 for every 1 cm increase in size (odds ratio = 1.73; 95% confidence interval = 1.46-2.03). Tumor size >2 cm (P < .001), perineural invasion (P = .002), microvascular invasion (P < .001), and distant metastases (P = .008) were independently associated with lymph node metastases. Tumor size >2 cm (P = .003), R1 status (P = .004), lymph node metastases (P < .001), and World Health Organization grade 3 (P = .002) were independently associated with disease-free survival. Aggressiveness rate was 13.1% in tumors ≤1 cm and 29% in tumors between 1.1 and 2 cm.

CONCLUSION

In resected sporadic nonfunctional pancreatic neuroendocrine tumors, the risk of lymph node metastases is correlated to tumor size. Considering that sporadic nonfunctional pancreatic neuroendocrine tumors between 1.1 and 2 cm had a higher risk of lymph node metastases and recurrence compared to tumors ≤1 cm, the decision to perform surgery in this subgroup of patients should be individualized in surgically fit patients.

Tumor-to-tumor metastasis: an extremely rare combination with renal cell carcinoma as the donor and a pancreatic neuroendocrine tumor as the recipient

BACKGROUND

Tumor-to-tumor metastasis is a rare phenomenon in which primary tumor cells metastasize hematogenously into another tumor. Herein, we report an extremely rare case of a renal cell carcinoma metastasis into a pancreatic neuroendocrine tumor exhibiting a tumor-to-tumor metastasis. Ours is the third reported case worldwide.

CASE PRESENTATION

The patient, a 72-year-old male, was referred to our hospital for further examination and treatment due to high levels of prostate-specific antigen. A left renal tumor and pancreatic head tumor were revealed incidentally on screening computed tomography. There were suspected to be a renal cell carcinoma and primary pancreatic neuroendocrine tumor or pancreatic metastasis from the renal cell carcinoma according to preoperative examination. The left nephrectomy and subtotal stomach-preserving pancreaticoduodenectomy were performed because of the pancreatic tumor indicated for operation in either case of diagnosis. Postoperative pathological examination showed a diagnosis of clear cell renal cell carcinoma for the left renal tumor. The pancreatic tumor was diagnosed with clear cell renal cell carcinoma metastasis into the pancreatic neuroendocrine tumor, that is to say tumor-to-tumor metastasis.

CONCLUSION

In some cases, conservative approach is selected for pancreatic neuroendocrine tumor patients who meet some requirements. However, if such patients exhibit tumor-to-tumor metastasis which combines with renal cell carcinoma and pancreatic neuroendocrine tumor as this case, conservative approach leads to progression of renal cell carcinoma. Therefore, conceiving the possibility of tumor-to-tumor metastasis, it is necessary to carefully choose a treatment plan for pancreatic neuroendocrine tumor patients associated with renal cell carcinoma, not easily choosing conservative approach.

Prognostic Factors of Small Non-Functional Pancreatic Neuroendocrine Tumors and the Risk of Lymph Node Metastasis: A Population-Level Study

BACKGROUND

Small non-functional neuroendocrine tumors (NF-PNETs) are a heterogeneous subset of tumors with controversy regarding their optimal management. We aimed to analyze the prognostic factors of patients with small NF-PNETs and create a risk score for lymph node metastasis (LNM).

METHODS

Data of 751 patients with NF-PNETs ≤ 2 cm were obtained from the Surveillance, Epidemiology, and End Results (SEER) database. Multivariate survival analysis was performed to analyze the prognostic factors. Logistic regression was used to identify risk factors for LNM.

RESULTS

Of the 751 patients, 99 (13.2%) were confirmed to have LNM. In multivariate survival analysis, LNM (hazard ratio [HR], 2.12; 95% CI, 1.04-4.32, p = 0.040) was independently associated with disease-specific survival. Logistic regression identified that tumor location in the head of the pancreas (odds ratio [OR], 4.33; 95% CI, 2.75-6.81; p < 0.001), size ≥ 1.5-2 cm (OR, 1.84; 95% CI, 1.17-2.87; p = 0.009), and grade III-IV (OR, 7.90; 95% CI, 1.79-34.90; p = 0.006) were independent risk factors of LNM. According to the OR value, the risk of LNM was scored as follows: a score of 1 for tumors located in the body/tail of the pancreas and 4 for those located in the head; a score of 1 for tumors <1 cm and 2 for those ≥1.5-2 cm; and a score of 1 for tumors with grade I-II and 8 for those with grade III-IV. Finally, the median score for this cohort was 4, with an interquartile range of 3-6. Therefore, patients were classified as three groups based on the risk score system: a total score of 1-3 for low risk, 4-6 for intermediate risk (OR, 2.98; 95% CI, 1.59-5.60; p = 0.001), and 7-14 for high risk (OR, 8.94; 95% CI, 4.50-17.7; p < 0.001), with an incidence of LNM 5.0%, 13.5%, and 31.8%, respectively (p < 0.001).

CONCLUSION

Surgical resection with regional lymphadenectomy is recommended for small NF-PNETs with malignant potential of LNM. A risk score for LNM based on tumor grade, location, and size may preoperatively predict LNM of small NF-PNETs and guide clinical practice.

Differentiation Between Solid Pseudopapillary Neoplasm of the Pancreas and Nonfunctional Pancreatic Neuroendocrine Neoplasm Using Endoscopic Ultrasound

OBJECTIVES

We investigated the utility of endoscopic ultrasound (EUS) for differentiating between solid pseudopapillary neoplasm of the pancreas (SPN) and pancreatic neuroendocrine neoplasm (PanNEN).

METHODS

A retrospective analysis was performed on 29 and 77 consecutive patients with pathologically proven SPN and nonfunctional PanNEN. In patients who underwent contrast-enhanced harmonic EUS (CH-EUS), lesions were classified into 3 vascular patterns (hypoechoic/isoechoic/hyperechoic), and the presence of "the alveolus nest sign," which we previously reported as a characteristic feature of SPN on CH-EUS, was also assessed.

RESULTS

Conventional EUS findings showed that calcification echoes were significantly more frequent in SPN lesions than in PanNEN lesions (19/29 [66%] vs 21/77 [27%], P = 0.001) as was internal isoechogenicity or hyperechogenicity (10/29 [34%] vs 11/77 [14%], P = 0.029). Contrast-enhanced harmonic EUS findings showed that SPN lesions more frequently had the isoechoic or hypoechoic vascular pattern, and significantly more frequently had the alveolus nest sign (18/25 [72%] vs 4/60 [7%], P < 0.001). In a multivariate analysis, the presence of the alveolus nest sign contributed the most to the SPN diagnosis (odds ratio, 70; 95% confidence interval, 6.2-786).

CONCLUSIONS

Endoscopic ultrasound, particularly the presence of the alveolus nest sign on CH-EUS, is useful for differentiating SPN from PanNEN.

The 3-Dimensional-Computed Tomography Texture Is Useful to Predict Pancreatic Neuroendocrine Tumor Grading

OBJECTIVES

The aim of this study is to evaluate the computed tomography texture parameters in predicting grading.

METHODS

This study analyzed 68 nonfunctioning pancreatic neuroendocrine neoplasms (Pan-NENs). Clinical and radiological parameters were studied. Four model models were built, including clinical and standard radiologic parameters (model 1), first- and second-order computed tomography features (models 2 and 3), all parameters (model 4). The diagnostic accuracy was reported as area under the curve. A score was computed using the best model and validated to predict progression-free survival.

RESULTS

The size of tumors and heterogeneous enhancement were related to the risk of "non-G1" Pan-NENs (coefficients 0.471, P = 0.012, and 1.508, P = 0.027). Four second-order parameters were significantly related to the presence of "non-G1" Pan-NENs: the gray level co-occurrence matrix correlation (6.771; P = 0.011), gray level co-occurrence matrix contrast variance (0.349; P = 0.009), the neighborhood gray-level different matrix contrast (-63.129; P = 0.001), and the gray-level zone length matrix with the low gray-level zone emphasis (-0.151; P = 0.049). Model 4 was the best, with a higher area under the curve (0.912; P = 0.005). The score obtained predicted the progression-free survival.

CONCLUSIONS

Computed tomography radiomics signature can be useful in preoperative workup.

Utility of contrast-enhanced harmonic endoscopic ultrasonography for predicting the prognosis of pancreatic neuroendocrine neoplasms

BACKGROUND AND AIMS

Pancreatic neuroendocrine neoplasms (PanNENs), including Grade 1 (G1) or G2 tumors, can have a poor prognosis. This study investigated the value of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) for predicting the prognosis of PanNENs.

METHODS

This single-center, retrospective study included 47 consecutive patients who underwent CH-EUS and were diagnosed with PanNEN by surgical resection or EUS-guided fine needle aspiration between December 2011 and February 2016. Patients were divided into aggressive and non-aggressive groups according to the degree of clinical malignancy. CH-EUS was assessed regarding its capacity for diagnosing aggressive PanNEN, the correspondence between contrast patterns and pathological features, and its ability to predict the prognosis of PanNEN.

RESULTS

There were 19 cases of aggressive PanNEN and 28 cases of non-aggressive PanNEN. The aggressive group included three G1, four G2, three G3 tumors, three mixed neuroendocrine non-neuroendocrine neoplasms, and six neuroendocrine carcinomas. CH-EUS was superior to contrast-enhanced computed tomography for the diagnosis of aggressive PanNEN (P < 0.001): hypo-enhancement on CH-EUS was an indicator of aggressive PanNEN, with sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 94.7%, 100%, 100%, 96.6%, and 97.9%, respectively. Among G1/G2 PanNENs, cases with hypo-enhancement on CH-EUS had a poorer prognosis than those with hyper/iso-enhancement (P = 0.0009). Assessment of 36 resected specimens showed that hypo-enhancement on CH-EUS was associated with smaller and fewer vessels and greater degree of fibrosis.

CONCLUSION

Contrast-enhanced harmonic endoscopic ultrasonography may be useful for predicting the prognosis of PanNENs.

Prediction of non-functioning pancreatic neuroendocrine tumor grades with fractal analysis of preoperative contrast-enhanced computed tomography images

PURPOSE

To assess intra-tumoral heterogeneity (ITH) via fractal analysis of preoperative contrast-enhanced computed tomography (CT) images to predict pathological grades in non-functioning pancreatic neuroendocrine tumors (NF-PNETs) and verify its impact on patient survival.

METHODS

This retrospective study enrolled 40 patients with NF-PNET resected in our institution during a period from July 2005 to December 2018, except functioning tumors, unidentified tumors in CT, patients without preoperative contrast-enhanced CT. CT images were analyzed using plugin software for calculating fractal dimension (FD), and the maximum value was denoted as "FDmax," and compared with pathological grades and patient survival between G1 and G2/3 group separating according to two different Ki-67 index thresholds (3% and 5%). All CT images were acquired in three-phases and arterial phase images were examined.

RESULTS

Ki-67 index and FDmax showed a direct correlation with significance (p < 0.01). The mean FDmax of the G2/3 tumor group was significantly higher than that of the G1 tumor group (p < 0.01 in both 3% and 5% thresholds). In the ROC analysis, FDmax showed 0.773 of AUC, and cut-off value of 1.036 reported 62.5 % sensitivity, 90.0 % specificity, 86.2 % PPV, and 70.6 % NPV to distinguish G2/3 patients. The high-FD (≥1.036) group showed a significantly shorter disease-free survival (DFS) than the low-FD group (p = 0.0128). In multivariate analysis of prognostic factors, high FD was the only significant factor for DFS (HR, 5.793; 95 % CI: 1.213-27.664; p = 0.028).

CONCLUSIONS

The tumor's FDmax using CE-CT analysis might be a potential biomarker for preoperative prediction of G2/3 tumors, and predicting recurrence.

A Direct Comparison of Patients With Hereditary and Sporadic Pancreatic Neuroendocrine Tumors: Evaluation of Clinical Course, Prognostic Factors and Genotype-Phenotype Correlations

Introduction

Pancreatic neuroendocrine tumors (PNETs) in hereditary syndromes pose a significant challenge to clinicians. The rarity of these syndromes and PNETs itself make it difficult to directly compare them with sporadic PNETs. Despite research suggesting differences between these two entities, the same approach is used in hereditary and sporadic PNETs.

Methods

We included 63 patients with hereditary PNET (GpNET) and 145 with sporadic PNET (SpNET) in a retrospective observational study. Clinical and genetic data were collected in two Polish endocrine departments from January 2004 to February 2020. Only patients with confirmed germline mutations were included in the GpNET cohort. We attempted to establish prognostic factors of metastases and overall survival in both groups and genotype-phenotype correlations in the GpNET group.

Results

Patients with GpNET were younger and diagnosed earlier, whereas their tumors were smaller and more frequently multifocal compared with patients with SpNET. Metastases occurred more frequently in the SpNET group, and their appearance was associated with tumor size in both groups. GpNET patients had longer overall survival (OS). OS was affected by age, age at diagnosis, sex, grade, stage, tumor diameter, occurrence and localization of metastases, type of treatment, and comorbidities. In the MEN1 group, carriers of frameshift with STOP codon, splice site, and missense mutations tended to have less advanced disease, while patients with mutations in exon 2 tended to have metastases more frequently.

Conclusions

Direct comparisons of GpNET and SpNET demonstrate significant differences in the clinical courses of both entities, which should force different approaches. A larger group of patients with GpNET should be assessed to confirm genotype-phenotype correlations.

Insights of Outcome after Resection of Small Nonfunctioning Neuroendocrine Pancreatic Tumors

Background

The incidence of small nonfunctioning neuroendocrine pancreatic tumors (NF-PNETs) has been increasing systematically in the last few decades. Surgical resection was once considered the treatment of choice but has been questioned in the direction of a more conservative approach for selected patients. Our aim was to analyze the outcome of surgical resection of small (≤3cm) NF-PNETs.

Methods

We retrospectively evaluated 14 patients with sporadic NF-PNETs who underwent pancreatic resection. Data were collected from patients' medical records.

Results

Of the 14 patients included, 35.71% were men, and the average age was 52.36 ± 20.36 years. Comorbidities were present in 92.86% of the cases. The incidence of postoperative complications was 42.86%, the 30-day mortality was zero, and the length of follow-up was 3.31 ± 3.0 years. The results of pathological evaluations revealed WHO grade I in 42.86% of cases, II in 21.43%, and neuroendocrine carcinoma in 35.71%. The median tumor size was 1.85cm (range, 0.5–3cm), and 2 cases had synchronous metastasis. The median TNM stage was IIa (range, I–IV). The disease-free and patient survival rates were 87.5% and 100% at 3 years and 43.75% and 75% at 10 years, respectively. The tumor pathological grade was significantly higher in head tumors than body-tail tumors, but there were no differences with respect to tumor size and TNM staging.

Conclusion

A surgical approach to treat small sporadic NF-PNETs is safe with low mortality and high patient survival. Based on these data, small pancreatic head tumors can be more aggressive, suggesting that surgical resection is still the best option to treat small nonfunctioning PNETS. Thus, conservative treatment should be indicated very cautiously for only cases with absolute contraindications for surgery.

Watchful waiting for small non-functional pancreatic neuroendocrine tumours: nationwide prospective cohort study (PANDORA)

This prospective nationwide cohort study examined the feasibility of a watchful-waiting protocol for non-functional pancreatic neuroendocrine tumours (NF-pNET) of 2 cm or smaller. In total, 8 of 76 patients (11 per cent) with a NF-pNET no larger than 2 cm showed significant tumour progression (more than 0.5 cm/year) during 17 months of follow-up, of whom two opted for resection. No patient developed metastases. Quality of life was poorer than in the reference population. Watchful waiting seems a safe alternative to upfront surgery in patients with a NF-pNET no larger than 2 cm, although longer follow-up is necessary.

Malignant potential of small pancreatic neuroendocrine neoplasm and its risk factors: A multicenter nationwide study

BACKGROUND

Pancreatic neuroendocrine neoplasms (PNENs) show heterogeneous biological behavior, and most small PNENs show indolent features. Consequently, selected cases can be considered for observation only, according to the National Comprehensive Cancer Network guideline, however, supporting clinical evidence is lacking. We investigated the clinical course of small PNENs and their risk factors for malignant potential.

METHODS

A total of 158 patients with small pathologically confirmed PNENs ≤2 cm in initial imaging were retrospectively enrolled from 14 institutions. The primary outcome was any metastasis or recurrence event during follow-up.

RESULTS

The median age was 57 years (range, 22-82 years), and 86 patients (54%) were female. The median tumor size at initial diagnosis was 13 mm (range, 7-20 mm). PNENs were pathologically confirmed by surgery in 137 patients and by EUS-guided fine needle aspiration biopsy (EUS-FNAB) in 21 patients. Eight patients underwent EUS-FNAB followed by surgical resection. The results of WHO grade were available in 150 patients, and revealed 123 grade 1, 25 grade 2, and 2 neuroendocrine carcinomas. A total of 145 patients (92%) underwent surgical resection, and three patients had regional lymph node metastasis. During the entire follow-up of median 45.6 months, 11 metastases or recurrences (7%) occurred. WHO grade 2 (HR 13.97, 95% CI 2.60-75.03, p = 0.002) was the only predictive factor for malignant potential in multivariable analysis.

CONCLUSIONS

WHO grade is responsible for the malignant potential of small PNENs ≤2 cm. Thus, EUS-FNAB could be recommended in order to provide early treatment strategies of small PNENs.

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.

Clinical relevance of performing endoscopic ultrasound-guided fine-needle biopsy for pancreatic neuroendocrine tumors less than 2 cm

BACKGROUND

We sought to define the diagnostic yield and concordance rates between endoscopic ultrasound (EUS)-fine-needle aspiration (FNA) and surgical pathology specimen following resection of pancreatic neuroendocrine tumors (pNET) less than 2 cm.

METHODS

Patients with a pNET less than 2 cm who underwent EUS-FNA were identified using a multi-institutional international database. Tumor differentiation, and Ki-67 index, as determined through EUS-FNA were examined and concordance rates between EUS-FNA and the surgical pathology were assessed.

RESULTS

Among 628 patients with a pNET less than 2 cm, 57.2% of patients had an EUS-FNA performed. Patients who underwent EUS had slightly smaller size tumors (1.3 vs 1.4 cm), and the pNETs were less likely to be functional (15.3% vs 26.8%) or symptomatic (48.5% vs 56.5%) (both P < .05). Among 314 patients with a pNET less than 2 cm who had an EUS-FNA performed at the time of diagnosis, 243 (73.2%) had the diagnosis confirmed by preoperative EUS-FNA. Tumor differentiation and Ki-67 could be determined by EUS-FNA in only 26.4% and 20.1% of patients, respectively. Concordance rate between EUS-FNA and pathology was high relative to tumor differentiation (92.7%) and Ki-67 (81.0%).

CONCLUSION

Tumor differentiation and Ki-67 index could be determined by EUS-FNA in only 26.4% and 20.1% of cases, respectively. Further studies should focus on EUS techniques to optimize diagnostic yield and cell extraction in the preoperative setting.

Surgical Principles in the Management of Pancreatic Neuroendocrine Neoplasms

OPINION STATEMENT

Pancreatic neuroendocrine neoplasms (PanNENs) are increasingly recognized entities, whose incidence has dramatically grown during the last two decades. Surgery plays a pivotal role in their management as it represents the only chance of cure. Since PanNENs display a wide range of aggressiveness, their surgical management needs to be tailored on tumor's and patient's characteristics. Currently, there are several open questions and burning issues in the field of PanNEN, such as the management of asymptomatic nonfunctioning pancreatic neuroendocrine tumors (NF-PanNET) ≤ 2 cm. An active surveillance of these small lesions has been demonstrated to be safe although the available evidences are only based on retrospective studies. On the other hand, formal pancreatic resection associated with lymphadenectomy represents the gold standard for patients with localized NF-PanNEN > 2 cm or NF-PanNEN ≤ 2 cm in the presence of symptoms, dilation of the main pancreatic duct or suspicion of nodal metastases. Surgery plays also an important role in the setting of metastatic disease. In particular, surgery is generally recommended in the presence of low-grade, resectable, metastatic disease, but several series have reported also a survival benefit of palliative primary tumor resection in patients with unresectable liver metastases. The role of surgery in PanNEN G3 is still controversial. Indeed, surgery is associated with an improved survival in patients with well-differentiated PanNET G3, whereas there is almost no survival benefit in case of poorly differentiated lesions.

Incidence and impact of Textbook Outcome among patients undergoing resection of pancreatic neuroendocrine tumors: Results of the US Neuroendocrine Tumor Study Group

BACKGROUND AND OBJECTIVES

We sought to define the incidence and impact of Textbook Outcome (TO) on disease-free survival [DFS] among patients undergoing resection of pancreatic neuroendocrine tumors (PNET).

METHODS

Patients undergoing resection of a PNET between 2000 and 2016 were identified using a multi-institutional database. TO was defined as no postoperative severe complications (Clavien-Dindo grade ≥ III), no 90-day mortality, no prolonged length-of-hospital stay (LOS) (ie, > 75th percentile), no 90-day readmission after discharge, and R0 resection. The 5-year DFS was calculated and the association with TO was examined.

RESULTS

Among 821 patients with a PNET, median tumor size was 2.1 cm (IQR 1.4-14.6). Resection consisted of pancreatoduodenectomy (PD) (n = 231, 28.1%), distal pancreatectomy (DP) (n = 492, 59.9%), and enucleation (EN) (n = 98, 11.9%). Overall TO rate was 49.3% (n = 405). The incidence of TO varied by procedure type (PD: 32.5% vs DP: 56.7% vs EN: 52.0%; P < .001). After adjusting for all competing factors, achievement of a TO was independently associated with improved DFS (hazard ratio: 0.54, 95% CI, 0.35-0.81; P = .003).

CONCLUSIONS

Only one in two patients undergoing resection of a PNET achieved a TO, which varied markedly based on procedure type. Achievement of a TO was associated with improved DFS.

Propensity score-matched analysis of clinical outcome after enucleation versus regular pancreatectomy in patients with small non-functional pancreatic neuroendocrine tumors

OBJECTIVES

The effectiveness of enucleation in treatment for low-grade (G1, G2) small (≤2 cm) non-functional pancreatic neuroendocrine tumors (sNF-pNETs) remains controversial. This study investigated short- and long-term outcome of enucleation comparing with regular pancreatectomy in patients with sNF-pNETs.

METHODS

The clinical data of patients with sNF-pNETs who underwent surgery in our hospital from January 2000 to December 2017 were retrospectively collected. Short- and long-term outcomes of two operations were analyzed. The propensity score matching (PSM) was performed to reduce potential selection bias.

RESULTS

A total of 123 patients with sNF-pNETs were enrolled with 62 males, 69 G1, and median age was 56.91 ± 10.04 years old. During the follow-up period (mean 87 ± 58.1 months), 9(7.32%) disease progressed (recurrence or metastasis) and 2 died (1.62%), 5-years OS was 100%, 5-years DFS was 91.4%. Both lymph node metastasis (p = 0.117) and pathological grade (p = 0.050) were not prognostic factors for sNF-pNETs. The propensity score-matched cohort comprised 27 patients with enucleation and 44 patients with regular pancreatectomy. Enucleation was noninferior to regular pancreatectomy in terms of DFS, before or after PSM. The surgical duration (P < 0.01) and blood loss (P < 0.01) significantly decreased in enucleation compared with regular pancreatectomy. The other postoperative complications tended to occur in regular pancreatectomy than in enucleation, but no statistically significant difference (all p > 0.05).

CONCLUSION

Enucleation seems to be an effective option for the treatment of sNF-pNETs with a lower total rate of postoperative complications and similar long-term prognosis, compared with regular pancreatectomy.

Histopathological diagnosis of appendiceal neuroendocrine neoplasms: when to perform a right hemicolectomy? A systematic review and meta-analysis

PURPOSE

The European Neuroendocrine Tumor Society (ENETS) guidelines advocate a right hemicolectomy (RHC) only in patients with appendiceal neuroendocrine neoplasms (aNENs) at risk for N+(node positive). The risk is defined using site, size, and grading of tumor as well as mesoappendiceal or lymphovascular invasion.

METHODS

A systematic review and meta-analysis was carried out. The data were reported using risk difference (RD) to define the risk of N+. The number needed to treat/harm (NNT/NNH) and the likelihood of being helped or harmed (LHH) were calculated using RD. Two strategies were considered: "to treat all" versus "to treat only patients having aNENs with risk stigmata". The aim was to evaluate the harm/benefit ratio related to the use of the ENETS lymph-nodal metastases (N+) risk factors.

RESULTS

Six studies were included involving a total of 261 patients. The RD (-0.30; P < 0.001) of N+ was significantly lower in aNENs ≤ 20 mm as compared to those >20 mm. One unnecessary RHC every five patients (NNT = 5) could be avoided while 1 patient with N+ every six patients (NNH = 6) remained untreated. The risk was lower than the benefits (LHH = 1.2). The RD NNT, NNH, and LHH values suggested that only a 15 mm cutoff and the presence of lymphovascular invasion could be considered useful.

CONCLUSIONS

An RHC should be performed in patients with aNENs >20 mm. The use of a 15 mm cutoff criterion had a similar outcome to that of a 20 mm cutoff. Lymphovascular invasion should only be considered a minor criterion. Selection based on other parameters should be avoided.

Ki-67 and presence of liver metastases identify different progression-risk classes in pancreatic neuroendocrine neoplasms (pNEN) undergoing resection

In pancreatic neuroendocrine neoplasms (pNEN), size ≤2 cm and Ki-67 < 3% suggest indolent behavior, but no factor alone predicts prognosis. We investigated factors predictive of tumor progression in 80 pNENs surgically resected in a single Institution from 1995 to 2015. At multivariable analysis the only two independent variables related to PFS were Ki-67 (HR 2.97; 95%CI 1.26-7.02) and presence of synchronous liver metastases (HR 3.60; 95%CI 1.70-7.61). Using Ki-67 < 3% and M0 as reference, the HR for tumor progression was 3.21 (95%CI 1.18-8.74) for M0 patients with Ki-67 3-20%, 5.06 (2.29-11.2) for M1 patients with Ki-67 ≤ 20% and 24.3 (6.64-89.2) for those with Ki-67 > 20%. Tumor size (≤2 vs. >2 cm) was not a predictive factor at any analysis. Intra-class correlation of Ki-67 values on pre-surgical biopsies vs. surgical specimens was 0.99 and Ki-67 classes were correctly identified in 97% of biopsies. Ki-67 and presence of liver metastases are the major prognostic factors in pNEN and identify different progression risks regardless of tumor size. Pre-surgical pNEN biopsy for Ki-67 assessment should be included in the evaluation of patients with 1-2 cm tumors to help in the decision on whether to perform surgical resection.

Outcomes after endoscopic ultrasound-guided ethanol-lipiodol ablation of small pancreatic neuroendocrine tumors

BACKGROUND AND AIM

Little is known about the standard care of small (<2 cm in diameter) pancreatic neuroendocrine tumors (PNET). The aim of the present study was to determine the clinical outcomes of small PNET after endoscopic ultrasound (EUS)-guided ethanol-lipiodol ablation (EUS-ELA).

METHODS

In this prospective cohort study, consecutive patients who underwent EUS-ELA for PNET were enrolled and were followed for ≥3 years. Treatment efficacy was the primary outcome measure.

RESULTS

In total, 33 patients who had 40 pathologically confirmed PNET (<2 cm in diameter) were enrolled for final analysis. A total of 63 EUS-ELA sessions were successfully carried out (mean, 1.9 sessions per patient, 1.6 sessions per tumor), which included 40 initial sessions and 23 repeated sessions owing to incomplete ablation. Median actual volume of ethanol-lipiodol mixture injected per session was 1.1 mL (IQR 0.8-1.9 mL). Complete ablation was achieved in 24 of 40 tumors (60%) with one (18 tumors, 45%) or two (24 tumors, 60%) sessions of EUS-ELA. Lipiodol retention within tumor had better treatment outcomes (P = 0.004). Rate of procedure-related adverse events was 3.2%. No malignancy or lymph node metastasis was discovered during a median follow up of 42 months (IQR 39-46 months).

CONCLUSIONS

We found that EUS-ELA was a safe and effective alternative option in the management of PNET <2.0 cm in diameter; 60% of patients achieved complete ablation. Lipiodol retention within tumor may be a useful early predictor of treatment effectiveness. Trial registered at ClinicalTrials.gov (NCT 01902238).

How should incidental NEN of the pancreas and gastrointestinal tract be followed?

Neuroendocrine gastro-entero-pancreatic neoplasms (GEP-NENs) constitute a heterogeneous group of tumors, whose incidence has increased over the years. The most frequent site for primary disease is the stomach followed by small and large intestine, and pancreas. In the last decade, a dramatic growing in the incidence of small, incidental GEP-NENs has been recorded. In parallel, an increasing attitude toward more conservative approaches instead of surgical management has being widely spreading. This is particularly true for small, asymptomatic, pancreatic NEN as for these tumor forms an active surveillance has proven to be safe and feasible. Primary site and biological features of the neoplasms lead to different strategies and indications for surveillance and follow-up. This review focuses on the current evidence on modality and timing of surveillance and conservative treatment of incidentally discovered lesions.

A novel liver metastasis-correlated protein of pancreatic neuroendocrine neoplasm (PanNEN) discovered by proteomic analysis

The aim of this study was to identify novel liver metastasis-correlated proteins of PanNEN by proteomics to compare pancreatic tumor (PT) with paired metastatic liver tumor (LT). Of 118 surgical cases with PanNEN, 7 cases with formalin-fixed paraffin-embedded (FFPE) tissues of both PT and paired LT were evaluated by proteomics. Tumor cells were selectively collected from FFPE tissues by laser capture microdissection. A total of 3,722 proteins were detected from extracted peptides by mass spectrometry-based shotgun analysis. Selection of the candidate proteins expressed differently between PT and LT were performed by semi-quantitative comparison in silico and confirmation with immunohistochemistry. We focused on ANXA6, CNPY2, RAB11B and TUBB3, all of which had higher expressions in LT. In all surgical cases with FFPE samples, liver recurrence-free survival (RFS) was evaluated in correlation to the expression of the candidate proteins in PT by immunohistochemistry. Liver RFS was significantly poorer in CNPY2 positive patients than in negative patients (10-year liver RFS; 39.8% vs. 92.3%, p = 0.012). Also, liver RFS tended to be poorer in ANXA6 positive patients than in those who were negative (10-year liver RFS; 51.4% vs. 95.0%, p = 0.099). In the multivariate analysis, the independent predictors of liver RFS were CNPY2 positivity (HR: 6.19, 95 % CI: 1.47-42.79, p = 0.011) and tumor size ≥ 42 mm (HR: 4.63, 95 % CI: 1.03-23.23, p = 0.045). In conclusion, CNPY2 is a novel liver metastasis-correlated protein of PanNEN.