The Landmark Series: Pancreatic Neuroendocrine Tumors

Diagnostics and Imaging for Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors originate from hormone-producing islet cells and have a propensity to metastasize to the liver once they reach 2 cm in size. Their diagnosis relies upon a combination of computed tomography, MRI, DOTATATE PET, and endoscopic ultrasound with or without tissue biopsy. Biochemical work-up is driven by patient symptoms of hormone excess.

Factors Affecting Nonfunctioning Small Pancreatic Neuroendocrine Neoplasms and Proposed New Treatment Strategies

BACKGROUND & AIMS

Despite previously reported treatment strategies for nonfunctioning small (≤20 mm) pancreatic neuroendocrine neoplasms (pNENs), uncertainties persist. We aimed to evaluate the surgically resected cases of nonfunctioning small pNENs (NF-spNENs) in a large Japanese cohort to elucidate an optimal treatment strategy for NF-spNENs.

METHODS

In this Japanese multicenter study, data were retrospectively collected from patients who underwent pancreatectomy between January 1996 and December 2019, were pathologically diagnosed with pNEN, and were treated according to the World Health Organization 2019 classification. Overall, 1490 patients met the eligibility criteria, and 1014 were included in the analysis cohort.

RESULTS

In the analysis cohort, 606 patients (59.8%) had NF-spNENs, with 82% classified as grade 1 (NET-G1) and 18% as grade 2 (NET-G2) or higher. The incidence of lymph node metastasis (N1) by grade was significantly higher in NET-G2 (G1: 3.1% vs G2: 15.0%). Independent factors contributing to N1 were NET-G2 or higher and tumor diameter ≥15 mm. The predictive ability of tumor size for N1 was high. Independent factors contributing to recurrence included multiple lesions, NET-G2 or higher, tumor diameter ≥15 mm, and N1. However, the independent factor contributing to survival was tumor grade (NET-G2 or higher). The appropriate timing for surgical resection of NET-G1 and NET-G2 or higher was when tumors were >20 and >10 mm, respectively. For neoplasms with unknown preoperative grades, tumor size >15 mm was considered appropriate.

CONCLUSIONS

NF-spNENs are heterogeneous with varying levels of malignancy. Therefore, treatment strategies based on tumor size alone can be unreliable; personalized treatment strategies that consider tumor grading are preferable.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Predicting resection margin status of pancreatic neuroendocrine tumors on CT: performance of NCCN resectability criteria

OBJECTIVE

To test the performance of the National Comprehensive Cancer Network (NCCN) CT resectability criteria for predicting the surgical margin status of pancreatic neuroendocrine tumor (PNET) and to identify factors associated with margin-positive resection.

METHODS

Eighty patients with pre-operative CT and upfront surgery were retrospectively enrolled. Two radiologists assessed the CT resectability (resectable [R], borderline resectable [BR], unresectable [UR]) of the PNET according to NCCN criteria. Logistic regression was used to identify factors associated with resection margin status. κ statistics were used to evaluate interreader agreements. Kaplan-Meier method with log-rank test was used to estimate and compare recurrence-free survival (RFS).

RESULTS

Forty-five patients (56.2%) received R0 resection and 35 (43.8%) received R1 or R2 resection. R0 resection rates were 63.6-64.2%, 20.0-33.3%, and 0% for R, BR, and UR diseases, respectively (all p ≤ 0.002), with a good interreader agreement (κ, 0.74). Tumor size (<2 cm, 2-4 cm, and >4 cm; odds ratio (OR), 9.042-18.110; all p ≤ 0.007) and NCCN BR/UR diseases (OR, 5.918; p = 0.032) were predictors for R1 or R2 resection. The R0 resection rate was 91.7% for R disease <2 cm and decreased for larger R disease. R0 resection and smaller tumor size in R disease improved RFS.

CONCLUSION

NCCN resectability criteria can stratify patients with PNET into distinct groups of R0 resectability. Adding tumor size to R disease substantially improves the prediction of R0 resection, especially for PNETs <2 cm.

ADVANCES IN KNOWLEDGE

Tumor size and radiologic resectability independently predicted margin status of PNETs.

Minimally Invasive vs Open Pancreatectomy for Pancreatic Neuroendocrine Tumors: Multi-Institutional 10-Year Experience of 1,023 Patients

BACKGROUND

Resection of pancreatic neuroendocrine tumors (PNETs) may be associated with adverse perioperative outcomes compared with pancreatic adenocarcinoma given the high-risk nature of soft glands with small pancreatic ducts. The effect of minimally invasive surgery (MIS) pancreatectomy on outcomes of PNETs remains to be examined, which is the aim of this study.

STUDY DESIGN

Between 2009 and 2019, 1,023 patients underwent pancreatectomy for PNETs at 4 institutions. Clinicopathologic data and perioperative outcomes of patients who underwent MIS (n = 447) and open resections (n = 576) were compared.

RESULTS

Of the 1,023 patients, 51% were male, the mean age was 58, the median tumor size was 2.1 cm, and 73% were grade 1 PNETs. There were 318 (31%) pancreatoduodenectomies (PDs), 541 (53%) distal pancreatectomies (DPs), 80 (7.8%) enucleation (ENs), 72 (7%) central pancreatectomies (CPs), and 12 (1.2%) total pancreatectomies. Almost half of the patients (N = 447, 44%) had MIS operations, of which 230 (51%) were robotic and 217 (49%) were laparoscopic. Compared with open operations, MIS PDs had significantly lower operative blood loss (150 vs 400 mL, p < 0.001) and rate of clinically relevant postoperative pancreatic fistulas (CR-POPFs; 13% vs 27%, p = 0.030), and MIS DPs had a shorter length of stay (5 vs 6 days, p < 0.001). Although MIS DPs and ENs had CR-POPFs comparable with open operations, MIS CPs had a higher CR-POPF rate (45% vs 15%, p = 0.013). After adjusting for pathological differences, MIS pancreatectomy was associated with recurrence-free survival and overall survival comparable with open pancreatectomy.

CONCLUSIONS

MIS pancreatectomy for PNETs is associated with improved outcomes or outcomes comparable with open resection.

Predicting Novel Drug Candidates for Pancreatic Neuroendocrine Tumors via Gene Signature Comparison and Connectivity Mapping

INTRODUCTION

There is a paucity of effective treatment options for advanced pancreatic neuroendocrine tumors (pNETs). Genome-wide analyses may allow for potential drugs to be identified based on differentially expressed genes (DEGs).

METHODS

Oligo microarray data of RNA expression profiling of pNETs and normal pancreas tissues were downloaded from the Gene Expression Omnibus. Functional and pathway enrichment information of the DEGs was obtained using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases. Corresponding homologous proteins were analyzed and potential therapeutic drugs for pNETs were identified using the Connectivity Map and Drug-Gene Interaction Database.

RESULTS

Assessment of raw data from 12,610 pNET genes demonstrated that 1082 and 380 genes were upregulated and downregulated, respectively, compared with normal pancreas tissue. Upregulated pathways were associated with nitrogen metabolism (i.e., GABAergic synapse, and graft-versus-host disease), whereas downregulated pathways included C-type leptin receptor signaling pathway, pertussis and AMPK signaling pathway. In particular, the protein-protein interaction analysis revealed 10 upregulated hub genes (DYNLL1, GNB5, GNB2, GNG4, GNAI2, GNAI1, HIST2H2BE, NUP107, NUP133, and SNAP25) and 10 downregulated hub genes (CXCL8, F2, CXCL2, GCG, SST, INS, GALR3, CCL20, ADRA2B, and CXCL6). Using the Drug-Gene Interaction Database, candidate drugs for pNETs treatment included 3 EGFR inhibitors (canertinib, erlotinib, WZ-4-145), as well as other cell-signaling pathway inhibitors such as AG-592, acarbose, lonidamine, azacytidine, rottlerin, and HU-211.

CONCLUSION

Using available genetic atlas data, potential drug candidates for treatment of pNETs were identified based on differentially expressed genes. These results may help focus efforts on identifying targeted agents with therapeutic efficacy to treat patients with pNETs.

Impact of tumor size and location on endoscopic ultrasound-guided sampling of pancreatic neuroendocrine tumors: A recursive partitioning analysis

BACKGROUND

Current guidelines provide weak recommendations to treat small (<2 cm) non-functional pancreatic neuroendocrine tumors with low Ki-67 proliferation index either by resection or clinical follow-up. However, there is a lack of consensus regarding the minimal size of pNET, which allows EUS-guided biopsy with high enough diagnostic accuracy for stratification.

METHODS

We conducted a retrospective, bicentric analysis of patients who had undergone EUS-guided pNET sampling in two tertiary care Endoscopy Units in Germany and Poland. Using a recursive partitioning of the tree-aided model, we aimed to stratify the probability of successful EUS-guided biopsy of pNET lesions according to their size and location.

RESULTS

In our pNET cohort, successful histological confirmation of a pNET diagnosis was achieved in 59/69 (85.5%) cases at the initial EUS-guided biopsy. In 41 patients with a pNET size less than 18.5 mm, the EUS-guided first biopsy was successful in 90.2%. In 16 of these patients with smaller lesions, EUS-guided sampling was 100% in very small (less than 11 mm) and extremely small lesions (less than 8 mm). The biopsy success rate was 100% in tail lesions in the size range between ≥5.95 and <8.1 mm but only 33.3% independent of the investigator in pancreatic head or body, with an error rate of 11.2% CONCLUSION: Using a recursive partitioning of the tree-aided stratification model, we demonstrate for the first time that in balancing risks and benefits, very small pNETs (<1 cm) in the tail of the pancreas should be sampled under EUS-guidance.

Organ preserving pancreatic resections offer better long-term conservation of pancreatic function at the expense of high perioperative major morbidity: a fair trade-off for benign or low malignant potential pancreatic neoplasms-a single-center experience

BACKGROUND

Standard pancreatic resections (SPRs) might have long-term deleterious effects on pancreatic function, without added oncological advantage in low malignant potential (LMP) or benign neoplasms. This study aimed to evaluate outcomes following organ-preserving pancreatic resections (OPPARs) and SPRs.

METHOD

Post hoc analysis of patients undergoing OPPAR or SPR for benign or LMP pancreatic tumors from January 2011 to January 2020 at Tata Memorial Hospital, Mumbai.

RESULTS

Thirty-six and 114 patients were identified in OPPAR and SPR groups respectively. The overall morbidity (58.3% vs 43.9%, p-0.129) was comparable. Major morbidity (41.7% vs 21.9%, p-0.020), post-operative pancreatic fistula (POPF) (63.9% vs 35.1%, p-0.002), and clinically relevant POPF (41.7% vs 20.2%, p-0.010) were significantly higher with OPPAR. Post-operative endocrine insufficiency (14.9% vs 11.1%, p-0.567), exocrine insufficiency (19.3% vs 0%, p-0.004), and requirement of long-term pancreatic enzyme replacement (17.5% vs 0%, p-0.007) were higher in SPRs. Comparing left-sided and right-sided resections in the entire cohort, incidence of endocrine insufficiency was 17.1% vs 11.2% (p-0.299) and that of exocrine insufficiency was 8.6% vs 20% (p-0.048) respectively.

CONCLUSION

OPPAR is associated with high post-operative major morbidity and pancreatic fistula rate but offers long-term benefit due to better preservation of pancreatic function than SPR. The incidence of exocrine insufficiency is higher in right sided as compared to left-sided pancreatic resections.

Surgical Treatment of Patients with Poorly Differentiated Pancreatic Neuroendocrine Carcinoma: An NCDB Analysis

BACKGROUND

Consensus guidelines discourage resection of poorly differentiated pancreatic neuroendocrine carcinoma (panNEC) given its association with poor long-term survival. This study assessed treatment patterns and outcomes for this rare malignancy using the National Cancer Database (NCDB).

METHODS

Patients with non-functional pancreatic neuroendocrine tumors in the NCDB (2004-2016) were categorized based on pathologic differentiation. Logistic and Cox proportional hazard regressions identified associations with resection and overall survival (OS). Survival was compared using Kaplan-Meier and log-rank tests.

RESULTS

Most patients (83%) in the cohort of 8560 patients had well-differentiated tumors (panNET). The median OS was 47 months (panNET, 63 months vs panNEC, 17 months; p < 0.001). Surgery was less likely for older patients (odds ratio [OR], 0.97), patients with panNEC (OR, 0.27), and patients with metastasis at diagnosis (OR, 0.08) (all p < 0.001). After propensity score-matching of these factors, surgical resection was associated with longer OS (82 vs 29 months; p < 0.001) and a decreased hazard of mortality (hazard ratio [HR], 0.37; p < 0.001). Surgery remained associated with longer OS when stratified by differentiation (98 vs 41 months for patients with panNET and 36 vs 8 months for patients with panNEC). Overall survival did not differ between patients with panNEC who underwent surgery and patients with panNET who did not (both 39 months; p = 0.294).

CONCLUSIONS

Poorly differentiated panNEC exhibits poorer survival than well-differentiated panNET. In the current cohort, surgical resection was strongly and independently associated with improved OS, suggesting that patients with panNEC who are suitable operative candidates should be considered for multimodality therapy, including surgery.

Simultaneous Resection of Pancreatic Neuroendocrine Tumors with Synchronous Liver Metastases: Safety and Oncological Efficacy

Simple Summary

Up to half of all newly diagnosed pancreatic neuroendocrine tumors (PNET) present with liver metastases (LM). The surgical resection of PNETs and LMs can provide complete tumor clearance and improve long-term survival. However, the combination of liver and pancreatic resection simultaneously can theoretically cumulate the morbidity and mortality of two separate operations. In the current study, we analyzed the outcomes of the synchronous surgical resection of PNETs and LMs in 51 patients. There were no differences in the postoperative outcomes in terms of mortality and morbidity according to the type of pancreatic resection. The tumor grade was identified as the sole prognostic factor for survival. The resection of well-differentiated PNETs with LMs was characterized by the longest survival rates (median overall survival 128 months, 5-year overall survival 83%). The optimal sequential surgical strategies for PNETs with LM and the use of neoadjuvant/adjuvant chemotherapy in this category of patients remain to be further investigated.

Abstract

Whether the simultaneous resection of pancreatic neuroendocrine tumors (PNET) with synchronous liver metastases (LM) is safe and oncologically efficacious remains to be debated. We retrospectively reviewed clinical data from patients who underwent the simultaneous resection of PNETs with LMs over the last 25 years. Fifty-one consecutive patients with a median age of 54 years (range 27–80 years) underwent pancreaticoduodenectomy (PD) (n = 16), distal pancreatosplenectomy (DSP) (n = 32) or total pancreatectomy (n = 3) with synchronous LM resection. There were no differences in the postoperative outcomes in term of mortality (p = 0.33) and morbidity (p = 0.76) between PD and DSP. The median overall survival (OS) was 64.78 months (95% CI: 49.7–119.8), and the overall survival rates at 1, 3, and 5 years were 97.9%, 86.2% and 61%, respectively. The OS varied according to the tumor grade (G): G1 (OS 128 months, 5-year OS 83%) vs. G2 (OS 60.5 months, 5-year OS 58%) vs. G3 (OS 49.7 months, 5-year OS 0%) (p = 0.03). Multivariate Cox analysis identified G as the only prognostic factor (HR: 5.56; 95% CI: 0.91–9.60; p = 0.01). Simultaneous PNETS with LMs can be performed safely with acceptable morbidity and mortality at tertiary centers. Well-differentiated PNETs had longer survival and might benefit the most from these extended surgeries.

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).

Comparison of phenotypes and outcomes following resection of incidental versus symptomatic pancreatic neuroendocrine tumors

Background/Aim Fifty to 70 percent of pancreatic neuroendocrine tumors are diagnosed incidentally. The objective of this study is to compare the phenotype and oncological outcomes of incidental versus symptomatic pancreatic neuroendocrine tumors. Methods A retrospective study was conducted identifying all incidental and symptomatic tumors resected between 2000 and 2019. Baseline characteristics, symptoms, operative variables and pathological stage were all recorded. In both groups, patterns of recurrence and overall and disease-free survival were analyzed. Results Fifty-one incidental and 45 symptomatic pancreatic tumor resections were performed. Symptomatic tumors were more frequent in women (29 vs 17; p=0.005), in younger patients (median years; 50 vs 58; p=0.012) and were detected at a more advanced stage (p=0.027). There were no differences in location and most resections (n= 49; 51%) were performed laparoscopically. There were no operative mortalities and 17 (17.7%) severe complications (≥IIIb on the Clavien-Dindo classification) were recorded with no differences between the two groups. With a median follow-up of 64.4 months (range 13.5 - 90), overall survival at 5 and 10 years was 89.7% and 72.8% for the non-incidental tumors, and 80.9% and 54.6% for the incidental tumors (p=ns). Disease-free survival in both groups (excluding M1a) was 71.2% and 47.5%, and 93.7% and 78.1%, respectively (p= ns). Conclusions Symptomatic tumors are more frequent in women and present at higher pathological stages. There were no significant differences in overall and disease-free survival between the two groups. Resection of incidental tumors ≥1.5 - 2 cm seems advisable, although each case should assessed on an individual basis.