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

Appropriate use of tissue sampling and somatostatin receptor PET imaging in the diagnosis of pancreatic neuroendocrine tumors: results of an International Delphi Consensus

BACKGROUND

Current guidelines lack clarity regarding the appropriate use of preoperative ultrasound-guided (EUS) biopsy and receptor positron emission tomography (SSTR PET) imaging for pancreatic neuroendocrine tumors (PNETs). This study aims to reach expert consensus on the optimal sequencing of SSTR PET and EUS biopsy in the diagnostic workup and management of patients with suspected PNETs.

METHODS

A three-round modified Delphi process was used. A multidisciplinary panel of experts was recruited via snowball sampling. A set of 22 baseline statements pertaining to diagnostic workup, imaging, and biopsy was developed based on literature review and feedback obtained through a focus group. Survey rounds were conducted electronically and anonymously. A panel of international experts was asked to indicate whether they agreed, disagreed, or lacked the appropriate background to answer each statement. Of the 55 experts invited, 38 (69%) accepted to participate. Consensus was achieved with > 80% agreement.

RESULTS

Response rates were 97%, 100%, and 100% in rounds 1, 2, and 3, respectively. Following rounds 1 and 2, 29 final statements achieved consensus in the following three domains: diagnostic workup (15 statements), imaging (nine statements), and tissue sampling (five statements). Cronbach's alpha value, a measure of internal consistency, was 0.91 and 0.85 for rounds 1 and 2, respectively. The final set of statements achieved a 95% approval rate in round 3.

CONCLUSION

This international Delphi study provides expert consensus-based guidance on the appropriate use of EUS biopsy in the diagnostic workup of PNETs in the era of SSTR PET imaging.

A comprehensive study on postoperative complications and postoperative pancreatic fistula in sporadic non-functional pancreatic neuroendocrine tumors: A retrospective cohort study

Backgrounds/Aims

Balancing surgical risks and benefits is crucial for managing non-functional pancreatic neuroendocrine tumors (NF-PNETs). Despite high postoperative pancreatic fistula (POPF) rates, studies on postoperative complications of sporadic NF-PNETs are scarce. Thus, this study aimed to investigate postoperative complications and identify risk factors for POPF.

Methods

A retrospective review of 166 NF-PNET surgeries performed at Severance Hospital between February 2000 and August 2023 was conducted.

Results

Age > 65 years and higher American Society of Anesthesiology (ASA) grade were not significantly correlated with severe complications (odds ratio [OR]: 1.10, p = 0.871 and OR: 1.47, p = 0.491, respectively). Surgical procedures included enucleation (13.9%), distal pancreatectomy (50.0%), central pancreatectomy (4.8%), pancreaticoduodenectomy (PD) (26.5%), and total pancreatectomy (4.8%). Severe complications occurred in 12.05% of surgeries. The overall incidence of all POPFs including biochemical leaks was 53%, while clinically relevant POPF (grade B or C) occurred in 7.8% of patients. Logistic regression showed that PD (OR: 3.94, p = 0.092) tended to be risk factor for POPF and that diameter of the main pancreatic duct (MPD) ≤ 3 mm was a significant risk factor for POPF (OR: 0.22, p = 0.008). A pancreas thickness (PT)/MPD ratio > 4.47 on preoperative computed tomography predicted all POPFs in PD patients (OR: 11.70, p = 0.001).

Conclusions

Age and comorbidities had no significant impact on surgical outcomes. PD was associated with higher serious complications and POPF rates. The PT/MPD ratio is a valuable preoperative tool for predicting POPF risk in PD patients.

Surgical vs. Conservative Management of Patients with Nonfunctioning Pancreatic Neuroendocrine Tumors Smaller than 2 cm (NF-PANNETs < 2 cm) Systematic Review and Meta-Analysis

INTRODUCTION

There is no consensus on managing non-functioning pancreatic neuroendocrine tumors smaller than 2 cm (NF-PANNETs < 2 cm). Therefore, their treatment remains controversial. The aim of this study, by literature review and meta-analysis, is to establish the best management of NF-PANNETs < 2 cm based on overall survival (OS) and cancer-specific survival (CSS).

MATERIALS AND METHODS

An extensive online search was conducted using the MEDLINE, EMBASE, Google Scholar, Scopus, Web of Science, and Cochrane Central databases. All retrospective and prospective studies were included in this study, comparing the outcomes of surgical management vs. conservative management in patients with NF-PANNETs < 2 cm. The pooled odds ratio and 95% CI for survival were calculated.

RESULTS

Six studies were included in the quantitative analysis, with 2708 patients managed operatively and 985 managed conservatively. A pooled analysis of all the data demonstrated increased OS in patients managed operatively compared with those managed conservatively at five years (OR = 1.77, 95% CI: 0.96 to 2.58; p = 0.002). In contrast, the meta-analysis did not demonstrate increased CSS in patients undergoing surgical resection compared with conservative management (OR = 1.01, 95% CI: -5.25 to 7.27; p = 0.56). Furthermore, analysis demonstrated a high heterogeneity for OS (Q = 43.98, p < 0.001, tau2 = 0.46, I2 = 88.63%) and for CSS (Q = 22.81, p < 0.0001, tau2 = 1.72, I2 = 91.23%).

CONCLUSION

This systematic review and meta-analysis indicated that surgical management of NF-PANNETs < 2 cm improves overall survival (OS) but does not significantly enhance cancer-specific survival (CSS). There is variability in outcomes among studies, and while surgery may help some patients, the lack of clear CSS benefits and associated risks call for individualized decision-making. Therefore, a conservative approach with active surveillance may be more suitable for low-risk patients.

The Landmark Series: Surgical Management of Functioning and Non-Functioning Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) are comparatively rare pancreatic malignancies that exhibit diverse biologic behavior, ranging from indolent tumors to widely metastatic cancers, with up to 15 % secreting hormones that cause symptoms. As a consequence, the management of PNETs is highly individualized and can include active surveillance of small (1-2 cm) and very small (< 1 cm) nonfunctioning tumors without worrisome features, parenchymal-sparing resection of appropriately located tumors, anatomic pancreatectomy and, in select cases, debulking of metastatic disease, particularly in the liver. This review synthesizes society recommendations and contemporary evidence guiding the surgical management of PNETs. Innovations in molecular profiling and systemic therapies hold promise to refine surgical algorithms for this heterogeneous tumor.

Ideal outcome after pancreatic resection for neuroendocrine tumors: a nationwide study

BACKGROUND

Pancreatic resections for pancreatic neuroendocrine tumors (pNET) may experience a higher complication rate than for pancreatic ductal adenocarcinoma (PDAC). This study aimed to determine the rate of the novel composite "Ideal Outcome" measure after resection for pNET, using PDAC as reference.

METHODS

This observational cohort study included all consecutive patients after pancreatic resection for pNET and PDAC using the nationwide Dutch Pancreatic Cancer Audit (2014-2021). The primary outcome was Ideal Outcome; absence of postoperative mortality, postoperative pancreatic fistulas (POPF) grade B/C, other major complications, prolonged length of stay, reoperations and readmissions.

RESULTS

In total, 524 pNET and 2851 PDAC resections were included. The rate of Ideal Outcome was lower after resection for pNET (47.7% versus 55.7%; P<0.001) as compared to PDAC. This difference was driven by a lower rate of Ideal Outcome after pancreatoduodenectomy for pNET (37.7% versus 56.3%; P<0.001), with no difference after left pancreatectomy (54.5% versus 52.5%; P=0.598). Among the individual components of Ideal Outcome after pancreatoduodenectomy, the largest difference was a four times higher rate of POPF (32.1% versus 7.9%; P<0.001) after resection of pNET.

CONCLUSION

Patients undergoing pancreatoduodenectomy for pNET have a reduced Ideal Outcome rate compared to patients with PDAC, related to a fourfold increased risk of POPF. This highlights the value of pNET-specific patient counseling and the need for effective POPF mitigation strategies.

Alternative lengthening of telomeres and Ki-67 proliferation index provide complementary information on recurrence risk after resection of pancreatic neuroendocrine tumors

Given the heterogeneous clinical behavior of pancreatic neuroendocrine tumors (pNETs), improved prognostic markers are needed to guide management and post-resection surveillance. Patients who underwent resection of large (≥3 cm) sporadic well-differentiated pNETs from 2000 to 2019 were identified. The Ki-67 proliferation index was determined using immunohistochemistry, and alternative lengthening of telomeres (ALT) status was assessed using fluorescence in situ hybridization. Recurrence-free and overall survival were estimated using Kaplan-Meier analysis. Multivariable Cox regression analysis evaluated factors associated with recurrence-free survival. A total of 106 patients were identified. ALT was positive in 57 (54%) and negative in 49 (46%). Ki-67 was ≥3% in 74 (70%) and <3% in 32 (30%). Tumors with Ki-67 ≥3% were more likely to be ALT positive (61% vs. 38%, p = .046). Stratifying by ALT status and Ki-67 proliferation index, median recurrence-free survival was 4.6 years for patients with ALT-positive/Ki-67 ≥3% tumors, 3.1 years for patients with ALT-positive/Ki-67 <3% tumors, 12.4 years for patients with ALT-negative/Ki-67 ≥3% tumors, and 20.2 years for patients with ALT-negative/Ki-67 <3% tumors (p < .001). Initial recurrence was distant in 82% and locoregional in 18%. Across all groups, overall survival was similar (p = .19). In multivariable analysis, advanced age, ALT positivity, perineural invasion, and lymph node metastases were associated with increased recurrence risk (all p < .05). ALT and Ki-67 provide complementary information on post-resection recurrence risk, which can guide subsequent surveillance and management strategies. These data support the incorporation of ALT testing into routine clinical practice.

Evaluation of the details and importance of lymphatic, microvascular, and perineural invasion in patients with non-functioning pancreatic neuroendocrine neoplasms based on tumor size and the 2022 World Health Organization classification: a 23-year retrospective analysis

BACKGROUND

Although, recently observation methods has been proposed as one of the treatment options for non-functioning pancreatic neuroendocrine neoplasms (NF-PanNENs), determining treatment strategies may be difficult for small and low-malignant NF-PanNENs; thus, clarifying the significance of lymphatic, microvascular, and perineural invasion in these patients is of great clinical importance. This study aimed to assess the incidence and role of lymphatic, microvascular, and perineural invasion in patients with NF-PanNENs based on tumor size and the 2022 World Health Organization classification.

METHODS

From 2000 to 2023, we retrospectively investigated the incidence of lymphatic, microvascular, and perineural invasion and their impact on recurrence in 80 patients who underwent curative resection and were diagnosed with NF-PanNENs.

RESULTS

Of the 80 patients, 14 (18%), 20 (25%), and six (9%) patients had lymphatic, microvascular, and perineural invasion. Patients with neuroendocrine tumor (NET) G1 had significantly fewer occurrences of lymphatic, microvascular, and perineural invasion than those with NET G2 (10%, 15%, and 7% vs. 40%, 55%, and 35%; all P < 0.05.). Patients with a tumor size < 20 mm had significantly lower rates of lymphatic and microvascular invasions than those with a tumor size ≥ 20 mm (12% and 17% vs 33% and 48%; P = 0.034 and 0.0073, respectively). In all patients, NET G2, tumor size ≥ 20 mm, local invasion T2-3, presence of lymph node metastasis, and presence of microvascular invasion were significant risk factors for shorter recurrence-free survival (RFS) (all P < 0.05). In patients with NET G1 and tumor size < 20 mm, five (10%), eight (16%), and four (8%) patients had lymphatic, microvascular, and perineural invasion. The presence of microvascular invasion was also an independent risk factor for RFS (P < 0.05).

CONCLUSIONS

Information on the frequency and role of lymphatic, microvascular, and perineural invasion based on tumor size and malignancy on recurrence may be useful when considering treatment strategies for small- and low-grade NF-PanNENs.

EUS-based intratumoral and peritumoral machine learning radiomics analysis for distinguishing pancreatic neuroendocrine tumors from pancreatic cancer

Objectives

This study aimed to develop and validate intratumoral, peritumoral, and combined radiomic models based on endoscopic ultrasonography (EUS) for retrospectively differentiating pancreatic neuroendocrine tumors (PNETs) from pancreatic cancer.

Methods

A total of 257 patients, including 151 with pancreatic cancer and 106 with PNETs, were retroactively enrolled after confirmation through pathological examination. These patients were randomized to either the training or test cohort in a ratio of 7:3. Radiomic features were extracted from the intratumoral and peritumoral regions from conventional EUS images. Following this, the radiomic features underwent dimensionality reduction through the utilization of the least absolute shrinkage and selection operator (LASSO) algorithm. Six machine learning algorithms were utilized to train prediction models employing features with nonzero coefficients. The optimum intratumoral radiomic model was identified and subsequently employed for further analysis. Furthermore, a combined radiomic model integrating both intratumoral and peritumoral radiomic features was established and assessed based on the same machine learning algorithm. Finally, a nomogram was constructed, integrating clinical signature and combined radiomics model.

Results

107 radiomic features were extracted from EUS and only those with nonzero coefficients were kept. Among the six radiomic models, the support vector machine (SVM) model had the highest performance with AUCs of 0.853 in the training cohort and 0.755 in the test cohort. A peritumoral radiomic model was developed and assessed, achieving an AUC of 0.841 in the training and 0.785 in the test cohorts. The amalgamated model, incorporating intratumoral and peritumoral radiomic features, exhibited superior predictive accuracy in both the training (AUC=0.861) and test (AUC=0.822) cohorts. These findings were validated using the Delong test. The calibration and decision curve analyses (DCA) of the combined radiomic model displayed exceptional accuracy and provided the greatest net benefit for clinical decision-making when compared to other models. Finally, the nomogram also achieved an excellent performance.

Conclusions

An efficient and accurate EUS-based radiomic model incorporating intratumoral and peritumoral radiomic features was proposed and validated to accurately distinguish PNETs from pancreatic cancer. This research has the potential to offer novel perspectives on enhancing the clinical utility of EUS in the prediction of PNETs.

Novel Surgical Initiatives in Gastroenteropancreatic Neuroendocrine Tumours

PURPOSE OF REVIEW

Neuroendocrine tumours (NET) are rare entities arising from hormone producing cells in the gastroentero-pancreatic (GEP) tract. Surgery is the most common treatment of GEP-NETs.

RECENT FINDINGS

Improvements in surgical techniques allow for more locally advanced and metastasised GEP-NETs to be resected. Laparoscopic and robotically--assisted approaches are increasingly being utilised in the resection of selected GEP-NETs and are facilitated by novel intraoperative tumour localisation tools and parenchyma-sparing methods. At the same time, some authors suggest that indications for formal resections of small well differentiated non-functioning pancreatic NETs and appendiceal NETs should be more restrictive. Advancements in surgery allows for tissue-sparing resections of GEP-NETs. Indications for surgical resection and the extent of the procedure are highly dependent on GEP-NET size, localisation and grading. Robotically assisted surgeries with intraoperative ultrasound and visualisation methods as well as vessel-sparing radical retrograde lymphadenectomies for small intestinal NETs seem to be the future of GEP-NET surgery.

NON-FUNCTIONING SPORADIC PANCREATIC NEUROENDOCRINE TUMOR IS AN INDEPENDENT RISK FACTOR FOR RECURRENCE AFTER SURGICAL TREATMENT

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) are uncommon and heterogeneous neoplasms, often exhibiting indolent biological behavior. Their incidence is rising, largely due to the widespread use of high-resolution imaging techniques, particularly influencing the diagnosis of sporadic non-functioning tumors, which account for up to 80% of cases. While surgical resection remains the only curative option, the impact of factors such as tumor grade, size, and type on prognosis and recurrence is still unclear.

AIMS

To investigate prognostic risk factors and outcomes in patients with sporadic PNETs treated surgically.

METHODS

A retrospective analysis was conducted on patients with sporadic PNETs who underwent pancreatic resection. Data were collected from medical records.

RESULTS

A total of 113 patients were included: 32 with non-functioning tumors (NF-PNETs), 70 with insulinomas, and 11 with other functioning tumors (OF-PNETs). Patients with insulinoma were significantly younger, had a higher BMI, lower prevalence of comorbidities and ASA scores, and underwent significantly more pancreatic enucleations compared to patients with OF-PNET and NF-PNET. The insulinoma group had more grade I tumors, smaller tumor diameter, lower TNM staging, and lower disease recurrence rates. In univariate analysis, age, tumor type, tumor size, and TNM staging were identified as potential risk factors for tumor recurrence. In multivariate analysis, only the NF-PNET type was identified as an independent prognostic factor for disease recurrence.

CONCLUSIONS

NF-PNETs are an independent prognostic risk factor for disease recurrence. This finding supports the need for closer follow-up of patients with small tumors who are selected for conservative management.

Diagnostic and prognostic biomarkers for pancreatic neuroendocrine neoplasms

This review examines the diagnostic and prognostic biomarkers for pancreatic neuroendocrine neoplasms (PanNENs), a heterogeneous group of tumors with expression of neuroendocrine markers. PanNENs include both well-differentiated pancreatic neuroendocrine tumors (PanNETs) and poorly differentiated pancreatic neuroendocrine carcinomas (PanNECs). The diagnosis is confirmed through markers such as chromogranin A, synaptophysin, and INSM1, which establish neuroendocrine differentiation. The World Health Organization classification categorizes PanNENs based on tumor differentiation and proliferative activity (Ki-67 and/or mitotic index) into well-differentiated PanNETs (grade 1 to grade 3) and poorly differentiated PanNECs. In most cases, the morphology and proliferation index are sufficient to distinguish PanNETs from PanNECs. However, distinguishing grade 3 PanNETs from PanNECs can be challenging on the basis of morphology and proliferative activity alone. Additional key diagnostic markers for distinguishing grade 3 PanNET from PanNEC include SSTR2A expression and molecular immunohistochemical markers such as p53, Rb1, menin, ATRX, and DAXX. PanNECs are by definition high-grade tumors with highly aggressive clinical behavior, while PanNETs have a variable prognosis that is difficult to predict using current biomarkers such as tumor grade and size. Several studies have shown that ATRX or DAXX loss is strongly associated with a higher risk of PanNET metastasis and recurrence. They are therefore key prognostic markers in PanNETs. In addition, chromosomal copy number variations can further help assess PanNET aggressiveness and prognosis. Molecular profiling is increasingly important for improving the diagnosis, treatment, and prognosis of PanNENs.

Advances in Management of Nonfunctional Pancreas Neuroendocrine Tumors

This article presents updates in the surgical management of non-functional sporadic pancreas neuroendocrine tumors NET, including considerations for assessment of biologic behavior to support decision-making, indications for surgery, and surgical approaches tailored to the unique nature of neuroendocrine tumors.

Portuguese Pancreatic Club Perspective on the Surveillance Strategy for Pancreatic Neuroendocrine Tumours: When and How to Do It?

Background

Pancreatic neuroendocrine tumours (pNETs) are a highly heterogeneous group of tumours with widely variable biological behaviour. The incidence of pNETs has risen exponentially over the last three decades, particularly for asymptomatic small pNETs (≤2 cm), due to the widespread use of cross-sectional imaging in clinical practice.

Summary

Current consensus guidelines suggest that incidentally discovered pNETs ≤2 cm can be selectively followed due to the overall low risk of malignancy. Nevertheless, the "watch-and-wait" management strategy for small asymptomatic pNETs is still not widely accepted due to the lack of long-term data on the natural history of these small lesions. Additionally, it is clear that a subset of small pNETs may show malignant behaviour.

Key Message

Given the non-negligible risk of malignancy even in small pNETs, it is of the utmost importance to identify other preoperative factors, other than size, that may help to stratify the risk of malignant behaviour and guide clinical management. In this article, the Portuguese Pancreatic Club reviews the importance of risk stratification of pNETs and presents an updated perspective on the surveillance strategy for sporadic well-differentiated pNETs.

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.

Update in the management of gastroenteropancreatic neuroendocrine tumors

Neuroendocrine neoplasms are a diverse group of neoplasms that can occur in various areas throughout the body. Well-differentiated neuroendocrine tumors (NETs) most often arise in the gastrointestinal tract, termed gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Although GEP-NETs are still uncommon, their incidence and prevalence have been steadily increasing over the past decades. The primary treatment for GEP-NETs is surgery, which offers the best chance for a cure. However, because GEP-NETs are often slow-growing and do not cause symptoms until they have spread widely, curative surgery is not always an option. Significant advances have been made in systemic and locoregional treatment options in recent years, including peptide-receptor radionuclide therapy with α and β emitters, somatostatin analogs, chemotherapy, and targeted molecular therapies.

[Gastroenteropancreatic neuroendocrine neoplasms-Surgery in a multimodal concept]

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) are mainly found in the small intestine and pancreas. The course of the disease in patients is highly variable and depends on the degree of differentiation (G1-G3) of the neoplasm. The potential for metastasis formation of GEP-NEN is high even with good differentiation (G1). Lymph node metastases and, in many cases, liver metastases are also often found. Less common are bone metastases or peritoneal carcinomas. The treatment of these GEP-NENs is surgical, whenever possible. If an R0 resection with removal of all lymph node and liver metastases is successful, the prognosis of the patients is excellent. Patients with diffuse liver or bone metastases can no longer be cured by surgery alone. The long-term survival of these patients is nowadays possible due to the availability of drugs (e.g., somatostatin analogues, tyrosine kinase inhibitors), peptide receptor radionuclide therapy (PRRT) and liver-directed procedures, with a good quality of life.

The Value of Textbook Outcome in Benchmarking Pancreatoduodenectomy for Nonfunctioning Pancreatic Neuroendocrine Tumors

BACKGROUND

Textbook outcome (TO) is a composite variable that can define the quality of pancreatic surgery. The aim of this study is to evaluate TO after pancreatoduodenectomy (PD) for nonfunctioning pancreatic neuroendocrine tumors (NF-PanNETs).

PATIENTS AND METHODS

All patients who underwent PD for NF-PanNETs (2007-2016) in different centers were included in this retrospective study. TO was defined as the absence of severe postoperative complications and mortality, length of hospital stay ≤ 19 days, R0 resection, and at least 12 lymph nodes harvested.

RESULTS

Overall, 477 patients were included. The TO rate was 32%. Tumor size [odds ratio (OR) 1.696; p = 0.013], a minimally invasive approach (OR 12.896; p = 0.001), and surgical volume (OR 2.062; p = 0.023) were independent predictors of TO. The annual frequency of PDs increased over time as well as the overall rate of TO. At a median follow-up of 44 months, patients who achieved TO had similar disease-free (p = 0.487) and overall survival (p = 0.433) rates compared with patients who did not achieve TO. TO rate in patients with NF-PanNET > 2 cm was 35% versus 27% in patients with NF-PanNET ≤ 2 cm (p = 0.044). Considering only NF-PanNETs > 2 cm, patients with TO and those without TO had comparable 5-year overall survival rates (p = 0.766) CONCLUSIONS: TO is achieved in one-third of patients after PD for NF-PanNETs and is not associated with a benefit in terms of long-term survival.

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.

Contemporary Approaches to the Surgical Management of Pancreatic Neuroendocrine Tumors

The incidence of pancreatic neuroendocrine tumors (PNETs) is on the rise primarily due to the increasing use of cross-sectional imaging. Most of these incidentally detected lesions are non-functional PNETs with a small proportion of lesions being hormone-secreting, functional neoplasms. With recent advances in surgical approaches and systemic therapies, the management of PNETs have undergone a paradigm shift towards a more individualized approach. In this manuscript, we review the histologic classification and diagnostic approaches to both functional and non-functional PNETs. Additionally, we detail multidisciplinary approaches and surgical considerations tailored to the tumor's biology, location, and functionality based on recent evidence. We also discuss the complexities of metastatic disease, exploring liver-directed therapies and the evolving landscape of minimally invasive surgical techniques.

The results of surgery for renal cell carcinoma metastases of the pancreas

BACKGROUND

Pancreatic metastases from renal cell carcinoma (RCC) are rare. This study evaluated the surgical pathology and outcomes after resection of RCC metastases to the pancreas.

MATERIAL AND METHODS

A retrospective review of from 1 January 2011 to 31 December 2021, of patients who underwent pancreatic surgery for metastases from RCC. Data were retrieved from a prospectively managed database and patient demographics, comorbidities, pathology, perioperative outcomes, and overall survival were analyzed. Median overall survival (OS) and disease-free survival (DFS) were estimated by the Kaplan-Meier method.

RESULTS

There were 25 patients (17 males, 8 females, median age 66 range 51 - 79 year), all with metachronous metastases. Median time from resection of the primary to operation for pancreatic RCC was 95.6 (12.0 - 309.7) months. Twenty-four patients were operated with intended cure (four pancreaticoduodenectomies, three total pancreatectomies, 17 distal pancreatectomies) and one patient had abortive surgery due to dissemination. Postoperative surgical complications occurred in nine patients (36%), and one patient died during hospital stay. Eight patients (33.3%) developed exocrine and/or endocrine insufficiency after pancreatic resection. Fifteen patients (60%) had recurrence 21.7 (4.9 - 61.6) months after pancreatic operation. Five patients (25%) died from RCC during follow-up 46.3 (25.6 - 134.8) months after pancreatic resection. Five-year OS and DFS were83.6% and 32.3%, respectively. Median OS after pancreatic surgery was 134.8 months, independent of resection of previous extrapancreatic metastases.

CONCLUSIONS

Pancreatic resection for metastases from RCC offers favorable prognosis with a curative potential and should be considered a valuable treatment option even in the era of novel targeted treatment.

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.

Premalignant Lesions in the Kidney Transplant Candidate

End-stage kidney disease patients who are referred for transplant undergo an extensive evaluation process to ensure their health prior to transplant due in part to the shortage of available organs. Although management and surveillance guidelines exist for malignancies identified in the transplant and waitlist populations, less is written about the management of premalignant lesions in this population. This review covers the less common premalignant lesions (intraductal papillary mucinous neoplasm, gastrointestinal stromal tumor, thymoma, and pancreatic neuroendocrine tumor) that can be found in the transplant candidate population. High-level evidence for the management of these rarer premalignant lesions in the transplant population is lacking, and this review extrapolates evidence from the general population and should not be a substitute for a multidisciplinary discussion with medical and surgical oncologists.

Robotic enucleation & uncinectomy of complex lesions of the proximal pancreas

BACKGROUND

Malignant tumours within the proximal pancreas traditionally require pancreaticoduodenectomy (PD) for cure. For smaller lesions with borderline malignant potential the risk/benefit of PD becomes difficult to justify. Robotic approaches to these lesions allow for parenchymal preserving resection with reduced complication profile without oncological compromise.

METHODS

A review of a single surgeons prospectively collated database across two institutions of consecutive robotic enucleations or parenchyma preserving resections of the proximal pancreas was performed between July 2018 and October 2021. Standard demographic data, preoperative variables, intraoperative parameters, post-operative outcomes, morbidity and mortality were recorded.

RESULTS

Thirteen patients (8 female and 5 male) underwent robotic enucleation (EN) (8) and/or uncinectomy (UN) (5) in the proximal pancreas. Mean BMI was 32(kg/m2 ). Three patients (21%) underwent preoperative prophylactic pancreatic duct stenting. One patient required conversion to open. The median operative time in the EN group was 170 min (108-224 min) and the UN group was 160 min (110-204 min). The majority (8) of lesions were pNETs. Three lesions were IPMNs, with 1 solitary fibrous tumour and a serous cystic neoplasm (SCN) respectively. Median tumour size was 23 mm (11-58 mm) in the EN group, and 27 mm (17-38 mm) in the UN group. Ten of 13 patients had an R0 resection. There was no mortality in our series. Four (31%) patients across both groups developed clinically relevant POPF while none developed new endocrine or exocrine insufficiency. Average outpatient follow-up has been 6 months (1-18 months).

CONCLUSION

A robotic approach in proximal parenchymal preserving pancreatectomy is expanding, safe and feasible.

European Neuroendocrine Tumour Society (ENETS) 2023 guidance paper for nonfunctioning pancreatic neuroendocrine tumours

This ENETS guidance paper for well-differentiated nonfunctioning pancreatic neuroendocrine tumours (NF-Pan-NET) has been developed by a multidisciplinary working group, and provides up-to-date and practical advice on the management of these tumours. Using the extensive experience of centres treating patients with NF-Pan-NEN, the authors of this guidance paper discuss 10 troublesome questions in everyday clinical practice. Our many years of experience in this field are still being verified in the light of the results of new clinical, which set new ways of proceeding in NEN. The treatment of NF-Pan-NEN still requires a decision of a multidisciplinary team of specialists in the field of neuroendocrine neoplasms.

Outcome of nonfunctioning pancreatic neuroendocrine tumors after initial surveillance or surgical resection: a single-center observational study

Background

Current guidelines consider observation a reasonable strategy for G1 or G2 nonfunctional pancreatic neuroendocrine tumors (nf pNETs) ≤2 cm. We aimed to characterize their natural behavior and confront the data with the outcomes of patients undergoing upfront surgery.

Methods

Data from patients with histologically confirmed nf pNETs ≤2 cm, managed at a single tertiary referral center between 2002 and 2020, were retrospectively reviewed.

Results

Thirty-nine patients (mean age 62.1 years, 56% male) with 43 lesions (mean size 12.7±3.9 mm; 32 grade 1 [G1] and 7 grade 2 lesions [G2]) were managed by careful surveillance. Progression was observed in 15 lesions (35%; mean follow up 47 months). Six patients (18%) underwent secondary surgery because of an increase in tumor size or dilation of the main pancreatic duct; 3 of them had lymph node metastasis in the resected specimen. Surgery was followed by pancreatic fistula in 2/6 patients, 1 of whom died. Fourteen patients (mean age 59 years, 64.3% female, mean size of lesions 11.4±3.1 mm) underwent pancreatic surgery immediately after diagnosis. The surgery-associated complication rate was 57.1% (8/14). Of the 14 patients, 13 remained recurrence free (mean follow up 67 months). Recurrent metastatic disease was observed 3 years after pancreaticoduodenectomy (R0, 15 mm G2 lesion, 0 N+/8 N) in 1 patient.

Conclusions

The behavior of small nf pNETs is difficult to predict, as there is evidence for malignant behavior in a subgroup of patients, even after surgical treatment. Optimal management remains challenging, as pancreatic surgery is associated with significant morbidity.

Understanding the increasing incidence of neuroendocrine tumors

INTRODUCTION

Neuroendocrine tumors (NETs) are a diverse group of tumors with origins from different primary sites such as gastro-entero-pancreatic, lung and endocrine tissue. Worldwide, their incidence has increased in recent decades. Advances in imaging and better clinical awareness are traditionally attributed to this trend; however, other factors such as genetic and environmental contributors are appreciated as well.

AREAS COVERED

The purpose of this article is to review the worldwide epidemiologic trends in incidence of NET through the decades and discuss the various factors potentially contributing to the observed changes in incidence trends.

EXPERT OPINION

Overall, the incidence of NET has increased across the globe over the last few decades. Although multiple genetics and environmental factors have been proposed, the majority of this increase in incidence is secondary to earlier detection. Future studies will help in more accurate assessments and an improved understanding of disease incidence among patients with different grades and differentiation.

Consensus of clinical diagnosis and treatment for non-functional pancreatic neuroendocrine neoplasms with diameter <2 cm

In clinical practice, pancreatic neuroendocrine neoplasms (pNENs) with a diameter smaller than 2 cm are commonly referred to as small pNENs. Due to their generally favorable biological characteristics, the diagnosis and treatment of small pNENs differ from other pNENs and are somewhat controversial. In response to this, the Chinese Pancreatic Surgery Association, Chinese Society of Surgery, Chinese Medical Association have developed a consensus on the diagnosis and treatment of small pNENs, which is based on evidence-based medicine and expert opinions. This consensus covers various topics, including concepts, disease assessment, treatment selection, follow-up, and other relevant aspects.

Status of Surveillance and Nonsurgical Therapy for Small Nonfunctioning Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) occur in < 1/100,000 patients and most are nonfunctioning (NF). Approximately 5% occur as part of multiple endocrine neoplasia type 1. Anatomic and molecular imaging have a pivotal role in the diagnosis, staging and active surveillance. Surgery is generally recommended for nonfunctional pancreatic neuroendocrine tumors (NF-PNETs) >2 cm to prevent metastases. For tumors ≤2 cm, active surveillance is a viable alternative. Tumor size and grade are important factors to guide management. Assessment of death domain-associated protein 6/alpha-thalassemia/mental retardation X-linked and alternative lengthening of telomeres are promising novel prognostic markers. This review summarizes the status of surveillance and nonsurgical management for small NF-PNETs, including factors that can guide management.

The Surgical and Therapeutic Activities of Non-Functional Pancreatic Neuroendocrine Tumors at a High-Volume Institution

BACKGROUND

This study aimed to summarize the surgical and therapeutic activities of non-functional pancreatic neuroendocrine tumors (NF-PanNETs) and perform survival analyses of a 15-year single-institutional cohort of NF-PanNETs.

METHODS

In total, 1001 patients with neuroendocrine neoplasms treated at Fudan University Shanghai Cancer Center were screened for inclusion, and 509 patients with NF-PanNETs from 2006 to 2020 were included. For time trend analyses, the 15-year study period was randomly divided into three periods. Survival analyses used the Kaplan-Meier method and Cox regression models.

RESULTS

The total number of resected NF-PanNETs increased over the 15-year study period, from 5 resections in 2006 to 94 resections in 2020. A significant decrease in the tumor size was observed, from a mean of 4.0 cm to 3.3 cm, and to 3.0 cm in the most recent period (p = 0.006). Minimally invasive techniques gradually increased from 3.5% to 12.9%, and finally to 46.4% in the most recent period (p < 0.001). In non-metastatic and resected tumors, the tumor size (p < 0.001), positive lymph node (p < 0.001), adjuvant treatment (p = 0.048), and tumor grade (p < 0.001) were independent prognostic factors for recurrence-free survival (RFS). The microvascular invasion (p = 0.024) and tumor grade (p = 0.013) were independent prognostic factors for overall survival (OS). A malignant transformation from NET into neuroendocrine carcinoma was observed.

CONCLUSIONS

An increasing number of NF-PanNETs resection and minimally invasive surgery was shown. In non-metastatic and resected tumors NF-PanNETs, tumor size, positive lymph node, adjuvant treatment, and tumor grade were independent predictors of RFS. Microvascular invasion and tumor grade were independent prognostic factors for OS.

Clinical Prediction Models for Recurrence in Patients with Resectable Grade 1 and 2 Sporadic Non-Functional Pancreatic Neuroendocrine Tumors: A Systematic Review

Recurrence after resection in patients with non-functional pancreatic neuroendocrine tumors (NF-pNET) has a considerable impact on overall survival. Accurate risk stratification will tailor optimal follow-up strategies. This systematic review assessed available prediction models, including their quality. This systematic review followed PRISMA and CHARMS guidelines. PubMed, Embase, and the Cochrane Library were searched up to December 2022 for studies that developed, updated, or validated prediction models for recurrence in resectable grade 1 or 2 NF-pNET. Studies were critically appraised. After screening 1883 studies, 14 studies with 3583 patients were included: 13 original prediction models and 1 prediction model validation. Four models were developed for preoperative and nine for postoperative use. Six models were presented as scoring systems, five as nomograms, and two as staging systems. The c statistic ranged from 0.67 to 0.94. The most frequently included predictors were tumor grade, tumor size, and lymph node positivity. Critical appraisal deemed all development studies as having a high risk of bias and the validation study as having a low risk of bias. This systematic review identified 13 prediction models for recurrence in resectable NF-pNET with external validations for 3 of them. External validation of prediction models improves their reliability and stimulates use in daily practice.

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.

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.

Endoscopic ultrasonography as additional preoperative workup is valuable in half of the patients with a pancreatic body or tail lesion

BACKGROUND

The management of pancreatic body and tail lesions is underexposed. It remains unclear whether endoscopic ultrasonography (EUS) increases the accuracy of the preoperative workup. This study assessed the diagnostic value and safety of EUS in addition to cross-sectional imaging in a surgical cohort of patients with pancreatic body or tail lesions.

METHODS

A multicenter retrospective cohort study was performed of patients who underwent distal pancreatectomy from 2010 to 2017. The composite primary outcome was the additional value of EUS, defined as: (a) EUS confirmed an uncertain diagnosis on cross-sectional imaging, (b) EUS was correct in case of discrepancy with cross-sectional imaging, or (c) EUS provided tissue diagnosis for neoadjuvant treatment. Furthermore, serious adverse events and needle tract seeding were assessed.

RESULTS

In total, 181 patients were included, of whom 123 (68%) underwent EUS besides cross-sectional imaging. Postoperative pathology was heterogeneous: 91 was malignant, 49 premalignant, 41 benign. Most lesions were solid (n = 117). EUS had additional value in 59/123 (48%) patients; 27/50 (54%) of cystic and 32/73 (44%) of solid lesions. No serious adverse event or needle tract seeding following EUS occurred.

CONCLUSION

EUS had additional value besides cross-sectional imaging in half of the patients and showed low associated risks.

Small pancreatic neuroendocrine tumours: observe and monitor or prompt surgical resection

Over recent decades there has been a significant increase in the annual incidence of neuroendocrine tumors of the pancreas (PanNets), from 0.4 to 0.8 per 100,000 inhabitants, due to the more widespread use of more sensitive imaging techniques (cross-sectional and functional imaging).

Progress in the Management of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors (PNETs) are a heterogeneous and orphan group of neoplasms that vary in their histology, clinical features, prognosis, and management. The treatment of PNETs is highly dependent on the stage at presentation, tumor grade and differentiation, presence of symptoms from hormonal overproduction or from local growth, tumor burden, and rate of progression. The US Food and Drug Administration has recently approved many novel treatments, which have altered decision making and positively impacted the care and prognosis of these patients. In this review, we focus on the significant progress made in the management of PNETs over the past decade, as well as the active areas of research. Expected final online publication date for the Annual Review of Medicine, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Identifying Risk Factors and Patterns for Early Recurrence of Pancreatic Neuroendocrine Tumors: A Multi-Institutional Study

Simple Summary

Approximately 30% of patients with a pancreatic neuroendocrine tumor (pNET) will develop metastases. Curative-intent treatment largely involves resection. Identifying patients with early recurrence (ER) following resection might help tailor adjuvant therapies and the surveillance intensity. The aim of this retrospective study was to determine an evidence-based cut-off value for ER, and to explore risk factors associated with ER. ER was identified 18 months after surgery. Tumor size (OR 1.20, 95% CI 1.05–1.37, p = 0.007) and positive lymph nodes (OR 4.69, 95%CI 1.41–15.58, p = 0.01) were independently associated with ER. Patients with ER had lower post-recurrence free survival and overall survival than patients with late recurrence. These data support intensive follow-up shortly after surgery, and adjuvant therapy may help improve survival in pNET patients with ER after surgery.

Abstract

Background: Identifying patients at risk for early recurrence (ER) following resection for pancreatic neuroendocrine tumors (pNETs) might help to tailor adjuvant therapies and surveillance intensity in the post-operative setting. Methods: Patients undergoing surgical resection for pNETs between 1998–2018 were identified using a multi-institutional database. Using a minimum p-value approach, optimal cut-off value of recurrence-free survival (RFS) was determined based on the difference in post-recurrence survival (PRS). Risk factors for early recurrence were identified. Results: Among 807 patients who underwent curative-intent resection for pNETs, the optimal length of RFS to define ER was identified at 18 months (lowest p-value of 0.019). Median RFS was 11.0 months (95% 8.5–12.60) among ER patients (n = 49) versus 41.0 months (95% CI: 35.0–45.9) among non-ER patients (n = 77). Median PRS was worse among ER patients compared with non-ER patients (42.6 months vs. 81.5 months, p = 0.04). On multivariable analysis, tumor size (OR: 1.20, 95% CI: 1.05–1.37, p = 0.007) and positive lymph nodes (OR: 4.69, 95% CI: 1.41–15.58, p = 0.01) were independently associated with ER. Conclusion: An evidence-based cut-off value for ER after surgery for pNET was defined at 18 months. These data emphasized the importance of close follow-up in the first two years after surgery.