Surgical strategies for non-functioning pancreatic neuroendocrine tumours

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.

Risk factors for lymph node metastasis in patients with pancreatic neuroendocrine neoplasms

BACKGROUND

Although PNENs generally have a better prognosis than pancreatic cancers, some PNENs display malignant behavior including lymph node (LN) metastasis. Complete tumor resection can be the only potentially curative treatment for patients with resectable PNENs. However, the indications for LN dissection are still controversial. Over the last decade, minimally invasive surgery such as laparoscopic pancreatic surgery (LPS) has been increasingly performed for pancreatic tumors including PNENs.

AIM

To investigate the risk factors for LN metastasis in PNENs and to select appropriate patients for limited surgery by LPS.

METHODS

From April 2001 to December 2019, 92 patients underwent pancreatic resection for PNENs at Kumamoto University Hospital. Finally, 82 patients were enrolled in this study. Using perioperative factors, we examined the predictive factors for LN metastasis in PNENs.

RESULTS

Among the 82 patients, the percentage of LN metastasis according to the pathological findings was 12% (10/82 cases). The median tumor size was 12 mm (range: 5-90 mm). The median tumor size in the LN-positive group (37 mm) was significantly larger than that in the LN-negative group (12 mm) (P = 0.0001). Multivariate analyses revealed that larger tumor size (≥ 20 mm) was an independent risk factor for LN metastasis (odds ratio 16.8, P = 0.0062). In patients with small tumors (≤ 10 mm), LN metastasis was not found.

CONCLUSION

Larger tumor size (≥ 20 mm) is an independent risk factor for LN metastasis in PNENs. In smaller PNENs (≤ 10 mm), we may be able to choose limited surgery without LN dissection.

Clinical Prognosticators of Metastatic Potential in Patients with Small Pancreatic Neuroendocrine Tumors

BACKGROUND

While observation of T1(≤2cm) nonfunctioning pancreatic neuroendocrine tumors (NF-PanNETs) is an accepted practice, an ill-defined subgroup of patients with T1 tumors develops metastases. This study aimed to identify those patients via clinical factors.

METHODS

Patients from the Surveillance, Epidemiology, and End Results (SEER) registry who were diagnosed with NF-PanNET with size ≤2cm between 1998 and 2014 and who underwent primary tumor resection were identified. Binary logistic regression analyses were performed to evaluate factors associated with pathological nodal and systemic metastatic disease.

RESULTS

A total of 612 patients with T1 NF-PanNETs were identified. Of those, 72 (11.7%) developed nodal metastasis and 35 (5.7%) distant metastasis (M1). In the multivariable analysis, tumor location in the pancreatic body (OR 1.903, p=0.03) (OR 1.407, p=0.038) or tail (OR 1.258, p=0.04) (OR 1.612, p=0.021); tumor grade III-IV (OR 2.042, p=0.022) (OR 5.379, p≤0.001); and younger age (OR 0.963, p=0.01) (OR 0.919, p=0.009) were associated with nodal metastases and the presence of M1 disease, respectively.

CONCLUSION

While the low metastatic potential of ≤2cm NF-PanNET implies watchful waiting to be an appropriate strategy for most patients, the increased risk of metastatic disease in younger patients with high grade (III-IV) body/tail tumors suggests individualized risk stratification to be optimal.

Systematic Review and Metaanalysis of Lymph Node Metastases of Resected Pancreatic Neuroendocrine Tumors

BACKGROUND

The optimal surgical strategy for pancreatic neuroendocrine tumors (PNETs) is unknown. However, current guidelines recommend a watch-and-wait strategy for small nonfunctional PNETs (NF-PNETs). The aim of this study is to investigate the risk stratification and prognostic significance of lymph node metastasis (LNM) of PNETs to guide decision-making for lymphadenectomy.

PATIENTS AND METHODS

The MEDLINE and Web of Science databases were systematically searched for studies reporting either risk factors of LNM in resected PNETs or survival of patients with LNM. The weighted average incidence of LNM was calculated according to tumor characteristics. Random-effects metaanalyses were performed, and pooled hazard ratios (HR) and their 95% confidence intervals (CI) were calculated to determine the impact of LNM on overall survival (OS). In subgroup analyses, NF-PNETs were assessed.

RESULTS

From a total of 5883 articles, 98 retrospective studies with 13,374 patients undergoing resection for PNET were included. In all PNETs, the weighted median rates of LNM were 11.5% for small (≤ 2 cm) PNETs and 15.8% for G1 PNETs. In NF-PNETs, the rates were 11.2% for small PNETs and 10.3% for G1 PNETs. LNM of all PNETs (HR 3.87, 95% CI 3.00-4.99, P < 0.001) and NF-PNETs (HR 4.98, 95% CI 2.81-8.83, P < 0.001) was associated with worse OS.

CONCLUSIONS

LNM is potentially prevalent even in small and well-differentiated PNETs and is associated with worse prognosis. A watch-and-wait strategy for small NF-PNETs should be reappraised, and oncologic resection with lymphadenectomy can be considered. Prospective and controlled studies are needed in the future.

Clinical and Molecular Risk Factors for Recurrence Following Radical Surgery of Well-Differentiated Pancreatic Neuroendocrine Tumors

Well-differentiated pancreatic neuroendocrine tumors are increasingly diagnosed neoplasms. For localized disease, surgery is the first-line therapy and is curative in most cases. However, although recurrence is a rare event, it can still occur up to 10 years from surgery, worsening the prognosis. Many clinical and pathological factors have been associated with recurrence; however, it is currently unclear how to accurately discern patients at risk for relapse of disease from those that should be considered cured. In this review, we focus on clinical, pathological, and molecular factors associated with recurrence and discuss available prediction tools to assess the risk of recurrence following surgery.

CT-Based Radiomics Score for Distinguishing Between Grade 1 and Grade 2 Nonfunctioning Pancreatic Neuroendocrine Tumors

OBJECTIVE. The objective of our study was to explore the relationship between a CT-based radiomics score and grade of nonfunctioning pancreatic neuroendocrine tumors (PNETs) and to evaluate the ability of a calculated CT radiomics score to distinguish between grade 1 and grade 2 nonfunctioning PNETs. MATERIALS AND METHODS. This retrospective study assessed 102 patients with surgically resected, pathologically confirmed nonfunctioning PNETs who underwent MDCT from January 2014 to December 2017. Radiomic methods were used to extract features from portal venous phase CT scans, and the least absolute shrinkage and selection operator (LASSO) method was used to select the features. Multivariate logistic regression models were used to analyze the association between the CT radiomics score and nonfunctioning PNET grades. The performance of the CT radiomics score was assessed on the basis of its discriminative ability and clinical usefulness. RESULTS. The CT radiomics score, which consisted of four selected features, was significantly associated with nonfunctioning PNET grades. Every 1-point increase in radiomics score was associated with a 57% increased risk of grade 2 disease. The score also showed high accuracy (AUC = 0.86 for all PNETs; AUC = 0.81 for PNETs ≤ 2 cm). The best cutoff point for maximal sensitivity and specificity was a CT radiomics score of -0.134. Decision curve analysis showed that the CT radiomics score is clinically useful. CONCLUSION. The CT radiomics score shows a significant association with the grade of nonfunctioning PNETs and provides a potentially valuable noninvasive tool for distinguishing between different grades of nonfunctioning PNET, especially among patients with tumors 2 cm or smaller.

Prediction of the aggressiveness of non-functional pancreatic neuroendocrine tumors based on the dual-tracer PET/CT

Background

Predicting the aggressive behavior of non-functional pancreatic neuroendocrine tumors (NF-PNET) remains controversial. We wanted to explore, in a prospective setting, whether the diagnostic accuracy can be improved by dual-tracer functional imaging ⁶⁸Ga-DOTANOC and ¹⁸F-FDG-PET/CT in patients with NF-PNETs.

Methods

Thirty-one patients with NF-PNET (90% asymptomatic) underwent PET-imaging with ¹⁸F-FDG and ⁶⁸Ga-DOTANOC, followed by surgery (n = 20), an endoscopic ultrasonography and fine-needle biopsy (n = 2) or follow-up (n = 9). A focal activity on PET/CT greater than the background that could not be identified as physiological activity was considered to indicate tumor tissue. The imaging results were compared to histopathology. The mean follow-up time was 31.3 months.

Results

Thirty-one patients presented a total of 53 lesions (40 histologically confirmed) on PET/CT. Thirty patients had a ⁶⁸Ga-DOTANOC-positive tumor (sensitivity 97%) and 10 patients had an ¹⁸F-FDG-positive tumor. In addition, one ⁶⁸Ga-DOTANOC-negative patient was ¹⁸F-FDG-positive. ¹⁸F-FDG-PET/CT was positive in 19% (3/16) of the G1 tumors, 63% (5/8) of the G2 tumors and 1/1 of the well-differentiated G3 tumor. ⁶⁸Ga-DOTANOC-PET/CT was positive in 94% of the G1 tumors, 100% of the G2 tumors and 1/1 of the well-differentiated G3 tumor. Two out of six (33%) of the patients with lymph node metastases (LN+) were ¹⁸F-FDG-positive. The ¹⁸F-FDG-PET/CT correlated with tumor Ki-67 (P = 0.021). Further, the Krenning score correlated with tumor Ki-67 (P = 0.013). ¹⁸F-FDG-positive tumors were significantly larger than the ¹⁸F-FDG-negative tumors (P = 0.012). ¹⁸F-FDG-PET/CT showed a positive predictive value of 78% in the detection of potentially aggressive tumors (G2, G3, or LN + PNETs); the negative predictive value was 69%.

Conclusions

¹⁸F-FDG-PET/CT is useful to predict tumor grade but not the LN+ of NF-PNETs. Patients with ¹⁸F-FDG-avid NF-PNETs should be referred for surgery. The ⁶⁸Ga-DOTANOC-PET/CT also has prognostic value since the Krenning score predicts the histopathological tumor grade.

Trial registration

The study has been registered at ClinicalTrials.gov; Non-functional Pancreatic NET and PET imaging, NCT02621541.

Impact of tumour size on metastasis and survival in patients with pancreatic neuroendocrine tumours (PNETs): A population based study

Background: The relationship between tumour size and metastasis rate is poorly recognized in patients with pancreatic neuroendocrine tumours (PNETs). The impact of tumour size on prognosis was controversial in previous investigations.

Methods: PNETs cases diagnosed from 1988 to 2013 were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. Clinicopathologic features were retrospectively analyzed. Survival was calculated by the Kaplan-Meier method. Multivariable Cox regression models with hazard ratios (HRs) were constructed to analyze survival outcomes and risk factors. Cubic spline analysis was used to assess relationship between tumor size and probability of metastasis.

Results: A total of 5424 patients were identified, 1226 (22.6%) with tumour size of 20mm or less. The probability of metastasis increased in a non-linear fashion with increasing tumour size. Univariate analysis showed that tumour size was significantly correlated with survival (P<0.001), no matter surgery was performed or not. However, subgroup analysis suggested this association to be linear for patients with localized and regional tumours (P<0.001), but stochastic in patients with distant stages (P=0.703). On multivariate analysis, tumour size was an indicator for metastasis (HR=1.010, 95%CI: 1.008-1.013, P<0.001) and size≤20mm was an independent prognostic factor for good survival. For tumours≤20mm, surgical treatment was associated with significantly improved survival (P<0.001).

Conclusions: Tumour size affects the probability of metastasis. Its prognostic impact on survival is restricted to patients with localized and regional disease. For patients with tumour size ≤20mm, surgical treatment should be considered preferably.

Predictive Value of Chromogranin A and a Pre-Operative Risk Score to Predict Recurrence After Resection of Pancreatic Neuroendocrine Tumors

INTRO

Chromogranin A (CgA) may be prognostic for patients with neuroendocrine tumors; however, the clinical utility of this test is unclear.

METHODS

Patients undergoing resection for pancreatic neuroendocrine tumors (pNET) were selected from the eight institutions of the US Neuroendocrine Tumor Study Group database. Cox regression was used to identify pre-operative variables that predicted recurrence-free survival (RFS), and those with p < 0.1 were included in a risk score. The risk score was tested in a unique subset of the overall cohort.

RESULTS

In the entire cohort of 287 patients, median follow-up time was 37 months, and 5-year RFS was 73%. Cox regression analysis identified four variables for inclusion in the risk score: CgA > 5x ULN (HR 4.3, p = 0.01), tumor grade 2/3 (HR 3.7, p = 0.01), resection for recurrent disease (HR 6.2, p < 0.01), and tumor size > 4 cm (HR 4.5, p = 0.1). Each variable was assigned 1 point. Risk-score testing in the unique validation cohort of 63 patients revealed a 95% negative predictive value for recurrence in patients with zero points.

DISCUSSION

This simple pre-operative risk scoring system resulted in a high degree of specificity for identifying patients at low-risk for tumor recurrence. This test can be utilized pre-operatively to aid informed decision-making.

Angiogenesis in Pancreatic Cancer: Pre-Clinical and Clinical Studies

Angiogenesis is a crucial event in tumor development and progression, occurring by different mechanisms and it is driven by pro- and anti-angiogenic molecules. Pancreatic cancer vascularization is characterized by a high microvascular density, impaired microvessel integrity and poor perfused vessels with heterogeneous distribution. In this review article, after a brief introduction on pancreatic cancer classification and on angiogenesis mechanisms involved in its progression, the pre-clinical and clinical trials conducted in pancreatic cancer treatment using anti-angiogenic inhibitors will be described. Finally, we will discuss the anti-angiogenic therapy paradox between the advantage to abolish vessel supply to block tumor growth and the disadvantage due to reduction of drug delivery at the same time. The purpose is to identify new anti-angiogenic molecules that may enhance treatment regimen.

Can we predict recurrence in WHO G1-G2 pancreatic neuroendocrine neoplasms? Results from a multi-institutional Spanish study

INTRODUCTION

Pancreatic neuroendocrine neoplasms (PNEN) are rare tumours and well differentiated PNEN are associated with relatively indolent physiological behaviour. For this reason, only few studies have investigated those factors associated with recurrence in this group of patients. The aim of this study is to analyse whether it is possible to predict tumour recurrence in World Health Organization (WHO) 2017 G1-G2 PNEN patients.

METHODS

This is a retrospective multi-institutional study. Patients submitted to pancreatic resection from 7 Spanish centres were reviewed. Only patients with WHO G1-G2 PNEN were included. Demographic and clinicopathological variables were analysed.

RESULTS

Data from 137 patients were reviewed. Median age was 59.2 (25-84) years. Recurrence of disease occurred in 19 (13.9%) patients. Median DFS was 55 months. At multivariate analysis, tumour size >20 mm, lymphnode metastasis and a new tumour grade 2 incorporating Ki-67 labelling index (LI) > 5% and mitotic index (MI) > 2 were independently associated with recurrence. We developed a risk score model with these three factors. High-risk patients had a significantly lower 5-year disease-specific survival compared to low-risk patients (70% vs 100%).

CONCLUSION

We propose a novel risk score for recurrence based on lymphnode metastasis, tumour size > 20 mm and a new grade 2 based on Ki-67 LI >5% and MI > 2. If 2 factors are present, patients have a higher risk for recurrence and a significantly poorer DSS, and therefore they should be closely monitored during follow-up. The role of adjuvant chemotherapy in these patients needs to be evaluated in clinical trials.

Lymphadenectomy in pancreatic neuroendocrine neoplasms: Why are we still debating?

Pancreatic Neuroendocrine Neoplasms (PNEN) are rare tumours exhibiting very heterogeneous behaviour. For these reasons, studies with high level of evidence are lacking. Whether lymphadenectomy should be performed for PNEN is a matter of debate. In this review, we perform a critical analysis of the available literature regarding the clinical significance of lymphnode metastases, the importance of lymphadenectomy, and the implications on disease-specific survival.

PROGNOSTIC FACTORS IN PATIENTS WITH SURGICAL RESECTION OF PANCREATIC NEUROENDOCRINE TUMOURS

CONTEXT

Pancreatic neuroendocrine tumours (PanNETs) are rare pancreatic neoplasms. PanNETs can be treated by multimodal approach including surgery, locoregional and systemic therapy.

OBJECTIVE

The aim of the present study is to evaluate predictive factors of overall survival in patients with PanNETs surgically treated at a single center.

SUBJECTS AND METHODS

The study group consisted of 120 patients with PanNETs who had undergone surgery at the Center of Digestive Diseases and Liver Transplantation of Fundeni Clinical Institute, Bucharest, Romania. Surgical resection of the primary tumor was performed in 110 patients.

RESULTS

Tumor size > 2 cm (p=0.048) (90% CI) lymph node involvement (p=0.048), ENET grade (p<0.001), distant metastases (p<0.001), Ki 67 index (<2%, 2-5%, 5-10%, 10-20%, >20%) (p<0.001) were identified as significant prognostic factors for OS on univariate analysis. Using multivariate Cox proportional regression model we found that distant metastases and Ki 67 index were independent risk factors for the survival outcome.

CONCLUSIONS

Surgery with curative intent should be considered in all cases if clinically appropriate and technically feasible. High grade (Ki67 index ≥10%) tumours were associated with a 2- fold increase in risk of death as compared to those with a Ki67 <10%.

Prognostic factors and survival after surgical resection of pancreatic neuroendocrine tumor with validation of established and modified staging systems

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) display wide heterogeneity with highly variable prognosis. This study aimed to identify variables related to survival after surgical resection of PNET.

METHODS

A total of 143 patients were identified from a prospectively maintained database. Patient characteristics were analyzed and prognostic factors for overall survival and progression-free survival were evaluated. The WHO, ENETS and AJCC scoring systems were applied to the cohort, and their ability to predict patient outcomes were compared.

RESULTS

Multivariate analysis found that female gender, lymph node metastases and increasing WHO 2010 grade to be independently associated with reduced overall survival (P < 0.05). Patients requiring multi-visceral resection or debulking surgery found to be associated with shortest survival. ROC analysis found the ENETS and AJCC scoring systems to be similarly predictive of 5-year overall survival. Modified Ki67 significantly improved its accuracy in predicting 5-year overall survival (AUROC: 0.699 vs 0.605; P < 0.01).

CONCLUSIONS

Multi-visceral or debulking surgery is associated with poor outcomes. There seems to be no significant difference between enucleation and anatomical segmental resection. Available scoring systems have reasonable accuracy in stratifying disease severity, with no system identified as being superior. Prognostic stratification with modified grading systems needs further validation before applied in clinical practice.

Clinical outcomes and prognostic factors of resected pancreatic neuroendocrine neoplasms: A single-center experience in China

The aim of the present study was to investigate the clinical, pathological and prognostic characteristics of Chinese patients with resected pancreatic neuroendocrine neoplasms (p-NENs). Data from patients who were surgically treated and pathologically diagnosed with p-NENs at the Department of Pancreatic Oncology of the Fudan University Shanghai Cancer Center (Shanghai, China), between January 2003 and July 2015, were evaluated using univariate and multivariate analyses. A total of 162 patients with p-NENs met the criteria of the present study and were included in the analysis. Patients with poorly differentiated pancreatic neuroendocrine carcinoma (p-NEC) exhibited a significantly increased rate of lymph node metastasis, as compared with patients with grade (G)1/G2 pancreatic neuroendocrine tumors (p-NETs) (62.5 vs. 20.5%, P=0.003). Univariate analysis identified that the following factors led to decreased overall survival (OS): Lymph node metastasis (P=0.001, vs. the absence of lymph node metastasis); distant metastasis (P=0.043, vs. the absence of distant metastasis); resection margin R1/R2 (P=0.030, vs. R0 resection); NEC G3 (P<0.001, vs. NET G1). Following the multivariate analysis, NEC G3 remained a statistically significant risk factor (HR=12.593; 95% CI, 3.476-45.622; P<0.001, vs. NET G1/G2). Furthermore, according to the proliferation marker protein Ki-67 staining index, assigning a grade using the proliferative index (G1, ≤5%; G2, >5-20%; G3, >20%) was more efficient for prognostic stratification compared with the European Neuroendocrine Tumor Society (Berlin, Germany)/World Health Organization (Geneva, Switzerland) 2010 grading classification. The present study indicated that p-NEC was an important predictor of decreased OS in Chinese patients. Furthermore, a Ki-67 staining index of 5% represented a more efficient value for the distinction between G1 and G2.

Surveillance strategy for small asymptomatic non-functional pancreatic neuroendocrine tumors - a systematic review and meta-analysis

BACKGROUND

Non-functional pancreatic neuroendocrine tumors (NF-PNET) are rare neoplasms being increasingly diagnosed. Surgical treatment or expectant management are both suggested for small NF-PNETs. The aim of this study was to evaluate the outcome of surveillance strategy for small NF-PNETs.

METHODS

A systematic search was performed up to March 2016 in MEDLINE, EMBASE and the Cochrane Library according to the PRISMA guidelines. Data was pooled using the random-effects model.

RESULTS

Nine articles including 344 patients with sporadic and 64 patients with MEN1 related NF-PNET were selected. Tumor growth was observed in 22% and 52%, development of metastases were reported on 0% and 9%, and rate of secondary surgical resection was 12% and 25% in patients with sporadic or MEN1 related NF-PNETs, respectively. All metastases (1 distant, 4 nodal) were reported by a single study in patients with MEN1. Reason for secondary surgery was tumor growth in half of patients undergoing surgery.

DISCUSSION

Expectant management of small asymptomatic, sporadic, NF-PNETs could be a reasonable option in highly selected patients. However, the level of evidence is low and longer follow-up is needed to identify patients could benefit from upfront surgery instead of expectant treatment.

Is surgery the best treatment for sporadic small (≤2 cm) non-functioning pancreatic neuroendocrine tumours? A single centre experience

BACKGOUND

There is currently there is substantial controversy regarding the best management of non-functioning pancreatic neuroendocrine tumours ≤2 cm.

METHODS

Retrospective study involving 102 surgically treated patients affected by non-functioning pancreatic neuroendocrine tumours. Patients having small tumours (≤2 cm) (Group A) and those having large tumours (>2 cm) (Group B) were compared regarding demographics, clinical and pathological factors with the aim of evaluating the risk of malignancy and survival times.

RESULTS

The small tumours were T3-4 in 11% and G2-3 in 36.6% of cases; lymph node and distant metastases were present in 31% and 8% of the cases, respectively. When small and large tumours were compared, significant differences were found in relation to the presence of symptoms (P = 0.012), tumour status (P > 0.001), grading (P > 0.001) and years lost due to disability (P = 0.002). Multivariate analysis of the factors predicting malignancy and survival times showed that tumour size was related only to grading (P < 0.001). The years of life lost and disability adjusted life years were influenced by age at of diagnosis, the presence of symptoms and years lost due to disability only by grading.

CONCLUSIONS

Tumour size alone did not seem to be reliable in predicting malignancy because, first, small tumours (≤2 cm) could present lymph node or distant metastases, and could be G2-3 in a non-negligible percentage of cases and second, their risk of malignancy and survival time are similar to large tumours. Additional parameters have to be considered in order to establish the proper management of small tumours, such as age at diagnosis, presence of symptoms and grading.

Significance of lymph node metastasis in pancreatic neuroendocrine tumor

PURPOSE

Pancreatic neuroendocrine tumor (PNET) is relatively rare and has a generally better prognosis than does pancreatic cancer. However, as its prognosis in patients with lymph node metastasis (LNM) is unclear, lymph node dissection for PNET is controversial. Our study aimed to clarify the significance of LNM in PNET.

METHODS

We retrospectively examined 83 PNET patients who underwent pancreatic resections with lymph node dissection at Kumamoto University Hospital, Saiseikai Kumamoto Hospital, and Kumamoto Regional Medical Center from April 2001 to December 2014. Their clinicopathological parameters were analyzed by the absence or presence of LNM, and with regard to the disease-free survival (DFS) and overall survival (OS). A predictive score of LNM was also made using the age, tumor size, primary tumor location, and tumor function.

RESULTS

Although the 5-year OS was 74.8% for LNM⁺ and 94.6% for LNM^- (P = 0.002), LNM was not an independent risk factor for the OS in a multivariate analysis. However, tumors larger than 1.8 cm were found to be an independent prognostic factor, and the cut-off value for the predictive score was 1.69.

CONCLUSIONS

Although LNM was not an independent prognostic factor, lymph node dissection is recommended for patients whose predictive score is larger than 1.69.

Surgical treatment of non-functioning pancreatic neuroendocrine tumours based on three clinical scenarios

INTRODUCTION

The treatment of patients with non-functioning pancreatic neuroendocrine tumours (NFPNET) is resection in locally pancreatic disease, or with resectable liver metastases. There is controversy about unresectable liver disease.

METHODS

We analysed the perioperative data and survival outcome of 63 patients who underwent resection of NFPNET between 1993 and 2012. They were divided into 3 scenarios: A, pancreatic resection (44patients); B, pancreatic and liver resection in synchronous resectable liver metastases (12patients); and C, pancreatic resection in synchronous unresectable liver metastases (6patients). The prognostic factors for survival and recurrence were studied.

RESULTS

Distal pancreatectomy (51%) and pancreaticoduodenectomy (38%) were more frequently performed. Associated surgery was required in 44% of patients, including synchronous liver resections in 9patients. Two patients received a liver transplant during follow-up. According to the WHO classification they were distributed into G1: 10 (16%), G2: 45 (71%), and G3: 8 (13%). The median hospital stay was 11days. Postoperative morbidity and mortality were 49% and 1.6%, respectively. At the closure of the study, 43 (68%) patients were still alive, with a mean actuarial survival of 9.6years. The WHO classification and tumour recurrence were risk factors of mortality in the multivariate analysis. The median actuarial survival by scenarios was 131months (A), 102months (B), and 75months (C) without statistically significant differences.

CONCLUSIONS

Surgical resection is the treatment for NFPNET without distant disease. Resectable liver metastases in well-differentiated tumours must be resected. The resection of the pancreatic tumour with unresectable synchronous liver metastasis must be considered in well-differentiated NFPNET. The WHO classification grade and recurrence are risk factors of long-term mortality.

Postoperative Complications, In-Hospital Mortality and 5-Year Survival After Surgical Resection for Patients with a Pancreatic Neuroendocrine Tumor: A Systematic Review

Studies on postoperative complications and survival in patients with pancreatic neuroendocrine tumors (pNET) are sparse and randomized controlled trials are not available. We reviewed all studies on postoperative complications and survival after resection of pNET. A systematic search was performed in the Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE from 2000-2013. Inclusion criteria were studies of resected pNET, which described postoperative complications separately for each surgical procedure and/or 5-year survival after resection. Prospective and retrospective studies were pooled separately and overall pooled if heterogeneity was below 75%. The random-effect model was used. Overall, 2643 studies were identified and after full-text analysis 62 studies were included. Pancreatic fistula (PF) rate of the prospective studies after tumor enucleation was 45%; PF-rates after distal pancreatectomy, pancreatoduodenectomy, or central pancreatectomy were, respectively, 14-14-58%. Delayed gastric emptying rates were, respectively, 5-5-18-16%. Postoperative hemorrhage rates were, respectively, 6-1-7-4%. In-hospital mortality rates were, respectively, 3-4-6-4%. The 5-year overall survival (OS) and disease-specific survival (DSS) of resected pNET without synchronous resected liver metastases were, respectively, 85-93%. Heterogeneity between included studies on 5-year OS in patients with synchronous resected liver metastases was too high to pool all studies. The 5-year DSS in patients with liver metastases was 80%. Morbidity after pancreatic resection for pNET was mainly caused by PF. Liver resection in patients with liver metastases seems to have a positive effect on DSS. To reduce heterogeneity, ISGPS criteria and uniform patient groups should be used in the analysis of postoperative outcome and survival.

Preoperative Identification of a Prognostic Factor for Pancreatic Neuroendocrine Tumors Using Multiphase Contrast-Enhanced Computed Tomography

OBJECTIVES

To find predictive factors among computed tomography (CT) findings to identify pancreatic neuroendocrine tumors G2 of World Health Organization classification.

METHODS

Thirty-seven patients with pancreatic neuroendocrine tumors underwent multiphase contrast enhanced CT (unenhanced, arterial, pancreatic, portal and equilibrium phase), and attenuation values and imaging findings were examined. A receiver operating characteristic curve analysis was performed, and association between imaging findings and World Health Organization classification was evaluated.

RESULTS

Mean CT attenuation value of NET G1 was significantly higher than that of NET G2 throughout the arterial, pancreatic, and portal phases. Receiver operating characteristic analysis according to tumor size revealed sensitivity: 83.3%, specificity: 92.0% and area under the curve (AUC): 0.853, whereas that of corrected true enhancement values in the pancreatic phase revealed sensitivity: 91.7%, specificity: 84.0% and AUC: 0.897, which showed the highest AUC. Specific CT findings, such as irregular tumor contour, vessel involvement, and cystic degeneration/necrosis, were significantly associated with NET G2, but not to the extent of CT attenuation value and tumor size.

CONCLUSIONS

The CT enhancement in the pancreatic phase, and irregularity, vessel involvement, and cystic degeneration/necrosis were significant predictors of NET G2. These parameters might help in differentiating between NET G1 and G2, providing a basis for appropriate treatment.

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.

Efficacy and cost-effectiveness of immediate surgery versus a wait-and-see strategy for sporadic nonfunctioning T1 pancreatic endocrine neoplasms

BACKGROUND

Whether patients with small (<2 cm), sporadic nonfunctioning pancreatic endocrine tumors (NF-PETs) should directly undergo pancreatic surgery or should be followed longitudinally to detect growth and malignancy still has to be defined.

STUDY DESIGN

Based on the pertinent literature of the past decade, a Markov model was developed to investigate this issue. In the wait-and-see strategy arm, surgery was performed if the tumor attained a size ≥2 cm or surpassed 20% of the initial size. In a Monte Carlo probabilistic analysis, 100 hypothetical patients undergoing a wait-and-see strategy were compared to 100 patients directly undergoing surgery, with the aim of investigating the efficacy and cost-effectiveness of the two strategies.

RESULTS

During the postdiagnostic lifetime, 63 NF-PETs in the wait-and-see group showed significant growth and underwent surgery: 38 were stage I, 10 were stage II, 15 were stage III and none were stage IV. In the base-case scenario, the mean life expectancy and quality-adjusted life expectancy were found to be superior after immediate surgery [26.1 years and 11.8 quality-adjusted life years (QALYs)] than with the wait-and-see strategy (22.1 years and 8.3 QALYs) as the consequence of ageing during the wait-and-see follow-up which increased mortality due to surgery, when surgery was needed. The model was sensitive to starting age and length of follow-up; in particular, for patients >65 years of age, the two strategies provided similar results but the wait-and-see strategy was more cost-effective.

CONCLUSIONS

The wait-and-see strategy for NF-PETs <2 cm represents a reasonable approach in patients over 65 years of age; otherwise, immediate surgery is preferable.

Aspirin inhibits cell viability and mTOR downstream signaling in gastroenteropancreatic and bronchopulmonary neuroendocrine tumor cells

AIM: To investigate the effect of aspirin on neuroendocrine tumor (NET) cell growth and signaling in vitro.

METHODS: Human pancreatic BON1, bronchopulmonary NCI-H727 and midgut GOT1 neuroendocrine tumor cells were treated with different concentrations of aspirin (from 0.001 to 5 mmol/L), and the resulting effects on metabolic activity/cell proliferation were measured using cell proliferation assays and SYBR-DNA-labeling after 72, 144 and 216 h of incubation. The effects of aspirin on the expression and phosphorylation of several critical proteins that are involved in the most common intracellular growth factor signaling pathways (especially Akt protein kinase B) and mammalian target of rapamycin (mTOR) were determined by Western blot analyses. Propidium iodide staining and flow cytometry were used to evaluate changes in cell cycle distribution and apoptosis. Statistical analysis was performed using a 2-tailed Student’s t-test to evaluate the proliferation assays and cell cycle analyses. The results are expressed as the mean ± SD of 3 or 4 independently performed experiments. Statistical significance was set at P < 0.05.

RESULTS: Treatment with aspirin suppressed the viability/proliferation of BON1, NCI-H727 and GOT1 cells in a time- and dose-dependent manner. Significant effects were observed at starting doses of 0.5-1 mmol/L and peaked at 5 mmol/L. For instance, after treatment with 1 mmol/L aspirin for 144 h, the viability of pancreatic BON1 cells decreased to 66% ± 13% (P < 0.05), the viability of bronchopulmonary NCI-H727 cells decreased to 53% ± 8% (P < 0.01) and the viability of midgut GOT1 cells decreased to 89% ± 6% (P < 0.01). These effects were associated with a decreased entry into the S phase, the induction of the cyclin-dependent kinase inhibitor p21 and reduced expression of cyclin-dependent kinase 4 and cyclin D3. Aspirin suppressed mTOR downstream signaling, evidenced by the reduced phosphorylation of the mTOR substrates 4E binding protein 1, serine/threonine kinase P70S6K and S6 ribosomal protein and inhibited glycogen synthase kinase 3 activity. We observed the (compensatory) activation of tuberous sclerosis 2, the serine/threonine specific protein kinase AKT and extracellular signal-regulated kinases.

CONCLUSION: Aspirin demonstrates promising anticancer properties for NETs in vitro. Further preclinical and clinical studies are needed.

Predictors of lymph node metastases and impact on survival in resected pancreatic neuroendocrine tumors: a single-center experience

BACKGROUND

Staging for pancreatic neuroendocrine tumors (PNET) considers tumor size and lymph node (LN) status; however, correlation with survival remains unclear.

METHODS

A single-institution database of patients with resected PNET was analyzed.

RESULTS

Of the 150 patients, incidentally discovered PNET was the most common presentation (42%). One hundred thirteen patients (75%) had LN data, 32 (28%) with positive LN (LN+). Procedure and tumor size did not predict LN+. Perineural invasion (P = .016) and lymphovascular (P < .001) invasion, however, were more common in LN+. Multivariate analysis showed poor/moderate differentiation predicted LN+. Median follow-up was 52 months and median overall survival was 225 months. Fifty-two patients (35%) developed recurrence and median disease-free survival (DFS) was 74 months. Only poor/moderate differentiation affected DFS.

CONCLUSIONS

PNET has an unclear prognosis based on variables factored into stage. In this study, tumor size did not predict LN+; furthermore, LN+ did not impact overall survival or DFS. Tumor differentiation appears to be more important in determining prognosis.

Nonfunctional pancreatic neuroendocrine tumors <2 cm on preoperative imaging are associated with a low incidence of nodal metastasis and an excellent overall survival

BACKGROUND

The optimal surgical management of small nonfunctional pancreatic neuroendocrine tumors (NF-PNETs) remains controversial. We sought to identify (1) clinicopathologic factors associated with survival in NF-PNETs and (2) preoperative tumor characteristics that can be used to determine which lesions require resection and lymph node (LN) harvest.

METHODS

The records of all 116 patients who underwent resection for NF-PNETs between 1989 and 2012 were reviewed retrospectively. Preoperative factors, operative data, pathology, surgical morbidity, and survival were analyzed.

RESULTS

The overall 5- and 10-year survival rates were 83.9 and 72.8 %, respectively. Negative LNs (p = 0.005), G1 or G2 histology (p = 0.033), and age <60 years (p = 0.002) correlated with better survival on multivariate analysis. The 10-year survival rate was 86.6 % for LN-negative patients (n = 73) and 34.1 % for LN-positive patients (n = 32). Tumor size ≥2 cm on preoperative imaging predicted nodal positivity with a sensitivity of 93.8 %. Positive LNs were found in 38.5 % of tumors ≥2 cm compared to only 7.4 % of tumors <2 cm.

CONCLUSIONS

LN status, a marker of systemic disease, was a highly significant predictor of survival in this series. Tumor size on preoperative imaging was predictive of nodal disease. Thus, it is reasonable to consider parenchyma-sparing resection or even close observation for NF-PNETs <2 cm.