The Landmark Series: Management of Small Bowel Neuroendocrine Tumors

Association Between Female Sex and Better Survival in Gastroenteropancreatic Neuroendocrine Tumors

INTRODUCTION

Studies conflict on whether sex influences survival in gastroenteropancreatic neuroendocrine tumors (GEP-NETs). GEP-NETs express receptors and genes responsive to female hormones. We hypothesized that women would have improved survival and this difference would be greater in premenopausal age women compared to older women.

MATERIALS AND METHODS

The National Cancer Database from 2004 to 2016 was queried for patients with GEP-NETs based on histologic code. Demographic, tumor, treatment, and socioeconomic characteristics were compared between men and women and age ≤45 or >65 y using Fisher's exact and Wilcoxon tests as appropriate. The primary endpoint was overall survival (OS), assessed by Kaplan-Meier survival analysis.

RESULTS

Included in the study were 73,521 patients with small bowel neuroendocrine tumors (SBNETs), gastric neuroendocrine tumors (GNETs), or pancreas neuroendocrine tumors (36,197 female, 37,324 male). Women lived longer regardless of primary site, with the largest difference in GNETs (median OS 139 versus 85 mo) and smallest in SBNETs (121 versus 116, P < 0.001 for both). While male patients more often had high grade and metastatic disease, female sex remained independently associated with improved OS after adjusting for confounders (hazard ratio 0.84, P < 0.001). In GNETs and SBNETs, female sex had a larger beneficial effect on OS in premenopausal than postmenopausal patients.

CONCLUSIONS

Women with GEP-NETs have improved survival over men, especially in the premenopausal age group. This may be due to a protective effect of female hormones; however, further studies are necessary to uncover the biologic basis of this difference.

Surgery as a Principle and Technical Consideration for Primary Tumor Resection of Small Bowel Neuroendocrine Tumors

Small bowel neuroendocrine tumors (SB-NETs) are increasingly identified and have become the most frequent entity among small bowel tumors. An increasing incidence, a high prevalence, and a prolonged survival with optimal modern multidisciplinary management makes SB-NETs a unique set of tumors to consider for surgical oncologists. The major goals of surgical treatment in the setting of SB-NET include control of tumor volume, control of endocrine secretion, and prevention of locoregional complications. Key considerations include assessment of multifocality and resection of mesenteric nodal masses with the use of mesenteric-sparing approaches and acceptance of R1 margins if necessary to clear disease while avoiding short bowel syndrome. A description through eight steps for consideration is presented to allow for systematic surgical planning and execution of resection. Moreover, some controversies and evolving considerations to the surgical principles and technical procedures remain. The role of primary tumor resection in the presence of (unresectable) liver metastasis is still unclear. Reports of feasibility of minimally invasive surgery are emerging, with undetermined selection criteria for appropriateness or long-term outcomes. Resection of SB-NETs should be considered in all patients fit for surgery and should follow principles to achieve surgical oncological control that is appropriate for the stage and tumor burden, considering the age and comorbidity of the individual patient.

Multiomic sequencing of paired primary and metastatic small bowel carcinoids

Background: Small bowel carcinoids are insidious tumors that are often metastatic when diagnosed. Limited mutation landscape studies of carcinoids indicate that these tumors have a relatively low mutational burden. The development of targeted therapies will depend upon the identification of mutations that drive the pathogenesis and metastasis of carcinoid tumors. Methods: Whole exome and RNA sequencing of 5 matched sets of normal tissue, primary small intestine carcinoid tumors, and liver metastases were investigated. Germline and somatic variants included: single nucleotide variants (SNVs), insertions/deletions (indels), structural variants, and copy number alterations (CNAs). The functional impact of mutations was predicted using Ensembl Variant Effect Predictor. Results: Large-scale CNAs were observed including the loss of chromosome 18 in all 5 metastases and 3/5 primary tumors. Certain somatic SNVs were metastasis-specific; including mutations in ATRX, CDKN1B, MXRA5 (leading to the activation of a cryptic splice site and loss of mRNA), SMARCA2, and the loss of UBE4B. Additional mutations in ATRX, and splice site loss of PYGL, leading to intron retention observed in primary and metastatic tumors. Conclusions: We observed novel mutations in primary/metastatic carcinoid tumor pairs, and some have been observed in other types of neuroendocrine tumors. We confirmed a previously observed loss of chromosome 18 and CDKN1B. Transcriptome sequencing added relevant information that would not have been appreciated with DNA sequencing alone. The detection of several splicing mutations on the DNA level and their consequences at the RNA level suggests that RNA splicing aberrations may be an important mechanism underlying carcinoid tumors.

Surgical aspects of small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (NETs) are a heterogeneous group of epithelial tumors with a predominant neuroendocrine differentiation. Although NETs are usually considered rare neoplasms, small intestinal NETs are the most common primary malignancy of the small bowel, with an increasing prevalence worldwide during the course of the past few decades. The indolent nature of these tumors often leads to a delayed diagnosis, resulting in over one-third of patients presenting with synchronous metastases. Primary tumor resection remains the only curative option for this type of tumor. In this review article, the various surgical aspects for the excision of small intestinal NETs are discussed.

Diagnostic Challenge of Small Bowel Neuroendocrine Tumor in a Young Female Patient

Neuroendocrine tumors (NETs) are rare cancers arising from neuroendocrine cells and are characterized by their ability to secrete functional hormones causing distinctive hormonal syndromes. The incidence of NET has increased over the years, and small bowel neuroendocrine tumor (SBNET) is one of the most challenging to detect due to its varied presentation and poor accessibility with traditional endoscopic methods. Patients with SBNET present with variable hormonal symptoms, such as diarrhea, flushing, and nonspecific abdominal pain, which often delay the diagnosis. We present the case of a young patient who underwent multidisciplinary workups leading to a successful diagnosis of SBNET promptly. The patient was a 31-year-old female who presented to the emergency department with complaints of nausea, vomiting, and sudden-onset, severe, sharp abdominal pain. CT scan of her abdomen showed an area of irregular intraluminal soft tissue density suspicious for a mass in the mid-small bowel. The patient's initial enteroscopy was normal. A video capsule endoscopy showed a small bowel mass, which was consistent with SBNET confirmed by pathology later. This case emphasizes the importance of considering SBNET as a differential diagnosis in young patients with nonspecific symptoms of abdominal pain and highlights the role of multidisciplinary approaches in achieving prompt diagnosis and treatment.

Association of Surgery and Chemotherapy in Stage IV Gastroenteropancreatic Neuroendocrine Carcinoma

INTRODUCTION

The survival benefit of chemotherapy for patients with metastatic gastroenteropancreatic neuroendocrine carcinomas (GEP-NECs) is well established. However, reasons for underutilization of chemotherapy are unknown.

METHODS

The National Cancer Database (NCDB) was queried for metastatic GEP-NECs from 2009 to 2016. The cohort was stratified by patients who had received chemotherapy and who did not receive chemotherapy. Demographic, socioeconomic, clinical, and treatment characteristics were captured. Multivariable logistic regression examined factors associated with chemotherapy utilization.

RESULTS

Of the 2367 stage IV GEP-NECs patients identified, 1647 (69.6%) received chemotherapy. Patients with primary site at colon and small bowel, age ≥75, no insurance, and ≥2 comorbidities were less likely to receive chemotherapy than patients with other primary sites, age <75, private insurance, and no comorbidities (P < 0.005). The small bowel and colon were the primary sites with the greatest percentage of patients who received surgery (46.4% and 41.8%, respectively). In these subgroup of patients, surgical intervention was also associated with lower probability of receiving chemotherapy (odds ratio = 0.60, P < 0.005).

CONCLUSIONS

About 30% of patients with metastatic GEP-NECs did not receive chemotherapy. Primary site location and receipt of surgery were significantly associated with receipt of chemotherapy, with NECs in small bowel and colon being more likely to receive surgery and less likely to receive chemotherapy. While surgery may be considered on an individual basis, increasing efforts to ensure patients with colon or small bowel NECs receive guideline-concordant chemotherapy will positively impact survival. In addition, interventions to improve health insurance coverage to increase receipt of chemotherapy are warranted.

Recurrent Gastrointestinal Pseudo-obstruction Because of Well-Differentiated Duodenal Neuroendocrine Tumor

A 56-year-old man presented with recurrent gastrointestinal obstruction. Computed tomography showed fluid-filled, distended stomach, small intestine, and large intestine. Extensive workup including esophagogastroduodenoscopy, colonoscopy, magnetic resonance enterography, push enteroscopy, and video capsule enteroscopy showed no mechanical obstruction. Endoscopic ultrasound-guided biopsy of peripancreatic nodes detected on ¹⁸F-fluorodeoxyglucose positron emission tomography revealed a duodenal neuroendocrine tumor. The lesion showed intense uptake on gallium-68 DOTATOC positron emission tomography-computed tomography scan. The patient underwent surgical resection of the tumor with resolution of bowel obstruction events. He had elevated pancreatic polypeptide levels, which are known to delay gastric emptying and could explain his symptoms.

Small bowel neuroendocrine neoplasm: what surgeons want to know

Neuroendocrine neoplasms of the small bowel are a diverse group of tumors with a broad spectrum of imaging findings and clinical implications. Most tumors originate in close proximity to the ileocecal valve and most commonly metastasize to the mesentery and liver. This review will highlight the imaging findings of primary and metastatic small bowel neuroendocrine neoplasm that are most relevant to the surgical team.

Risk factors for small intestinal adenocarcinomas that are common in the proximal small intestine

The frequency of primary small intestinal adenocarcinoma is increasing but is still low. Its frequency is approximately 3% of that of colorectal adenocarcinoma. Considering that the small intestine occupies 90% of the surface area of the gastrointestinal tract, small intestinal adenocarcinoma is very rare. The main site of small intestinal adenocarcinoma is the proximal small intestine. Based on this characteristic, dietary animal proteins/lipids and bile concentrations are implicated and reported to be involved in carcinogenesis. Since most nutrients are absorbed in the proximal small intestine, the effect of absorbable intestinal content is a suitable explanation for why small intestinal adenocarcinoma is more common in the proximal small intestine. The proportion of aerobic bacteria is high in the proximal small intestine, but the absolute number of bacteria is low. In addition, the length and density of villi are greater in the proximal small intestine. However, the involvement of villi is considered to be low because the number of small intestinal adenocarcinomas is much smaller than that of colorectal adenocarcinomas. On the other hand, the reason for the low incidence of small intestinal adenocarcinoma in the distal small intestine may be that immune organs reside there. Genetic and disease factors increase the likelihood of small intestinal adenocarcinoma. In carcinogenesis experiments in which the positions of the small and large intestines were exchanged, tumors still occurred in the large intestinal mucosa more often. In other words, the influence of the intestinal contents is small, and there is a large difference in epithelial properties between the small intestine and the large intestine. In conclusion, small intestinal adenocarcinoma is rare compared to large intestinal adenocarcinoma due to the nature of the epithelium. It is reasonable to assume that diet is a trigger for small intestinal adenocarcinoma.

Predictors and Outcomes of Minimally Invasive Surgery for Small Bowel Neuroendocrine Tumors : Minimally Invasive Surgery for SBNETs

BACKGROUND

Open surgical resection with regional lymphadenectomy is the standard of care for small bowel neuroendocrine tumors (SBNETs). There is no consensus on the role of minimally invasive surgery (MIS). This study aims to evaluate the current national trends for MIS in treating SBNETs and its association with lymph node (LN) yield.

METHODS

The National Cancer Database was queried for patients with Stage I-III SBNETs who underwent surgery from 2010-2017. Time trends were examined using the Cochran-Armitage test. Chi-square tests, t test, and multivariable logistic regression assessed associations of surgical approach with patient, clinical, and facility characteristics. Kaplan-Meier curves and propensity score weighted Cox proportional hazards model were used to examine survival.

RESULTS

Of the 11,367 patients with Stage I-III SBNETs, 46.5% (N = 5,298) underwent MIS. From 2010-2017, the proportion of MIS increased from 35.6% to 57.7% (P < 0.001). Patients of Stage I disease (OR = 1.23), Caucasian race (OR = 1.18), private insurance (OR = 1.29), and higher volume centers (OR = 1.29) were more likely to undergo MIS (all P < 0.02). The average number of LN harvested in the MIS cohort was greater than in the open surgery cohort (13.3 vs 11.8 LN, P < 0.001). MIS patients had shorter length of stay by 2 days compared to open surgery (5.4 vs 7.6 days, P < 0.001). LN yield ≥ 8 was associated with better survival (HR = 0.77, P < 0.001).

CONCLUSION

The utilization of a MIS approach to treat Stage I-III SBNETs has increased, especially at higher volume centers. We did not observe an inferior LN harvest with the MIS cohort compared to the open surgery cohort.

Resection Prolongs Overall Survival for Nonmetastatic Midgut Small Bowel Neuroendocrine Tumors: A National Cancer Data Base Study

OBJECTIVES

This study aimed to understand if resection (RS) for nonmetastatic small bowel neuroendocrine tumors (SBNETs) prolongs 5-year overall survival.

METHODS

Patients from National Cancer Data Base with primary histologically confirmed SBNETs from 2007 to 2016 were included. Patients younger than 18 years, with the disease in the duodenum/Meckel diverticulum or metastatic disease were excluded. We assessed 5-year survival rates using Kaplan-Meier curves and multivariate Cox proportional hazards regression after RS, nonresection surgical management (NRS), or no resection (NR). Multivariate models were adjusted with age, sex, race, insurance, Charlson-Deyo comorbidity score, academic facility, primary tumor location, clinical T, clinical N, stage, and grade.

RESULTS

We identified 4180 patients. On average, patients were 64 years old (standard deviation, 12 years), male (53%), and White (84%). The majority received RS (91.8%) as opposed to NRS (4.0%) or NR (4.2%). Patients who received RS versus NR had increased survival rates (84.2% vs 73.9%; univariate log-rank, P < 0.0001; multivariate hazard ratio, 0.73; 95% confidence interval, 0.53-0.99; P = 0.04). No statistical difference in survival was observed for NRS versus NR.

CONCLUSIONS

To our knowledge, this is the first national study to evaluate survival after RS for nonmetastatic SBNETs. Results suggest that RS of SBNETs may prolong 5-year survival.

Relationship between Primary Tumor Resection for Metastatic Small Intestine Neuroendocrine Tumors and Survival: A Propensity Score-Matched Analysis

BACKGROUND

At present, it has been controversial whether primary tumor resection (PTR) can bring survival advantage to patients with metastatic small intestine neuroendocrine tumors (SI-NETs). To answer this question, we conducted a retrospective cohort study to evaluate the effect of PTR on the survival of patients with metastatic SI-NETs.

METHODS

Information on SI-NETs patients from 2004 to 2015 was extracted from Surveillance, Epidemiology, and End Results (SEER) databases. Demographics, tumor characteristics, treatment, and survival were compared. Propensity score-matched (PSM) was used 1:1 in the filtered queue. Cox proportional hazard regression model was used to evaluate the correlation between PTR and treatment results.

RESULTS

Before PSM, survival analysis showed that PTR significantly prolonged the survival of metastatic SI-NETs patients. After PSM, there was no significant difference in overall survival (OS) and cancer-specific survival (CSS) between the PTR group and the non-PTR group. Multivariate analysis showed no significant difference in OS and CSS between the two groups (p > 0.05).

CONCLUSION

Our study shows that OS and CSS are comparable between the PTR group and the non-PTR group. Thus, we believe that PTR should not be actively performed on such patients. Meanwhile, it is undeniable that properly selected patients may also benefit from PTR. Therefore, prospective randomized controlled trials are still needed to verify the effect of PTR on patients in the future.

ASO Author Reflections: Indolent Growth and Small Bowel Neuroendocrine Tumor Management

Surgical treatment is central to management of small bowel neuroendocrine tumors (SBNETs). Current controversies include whether to resect asymptomatic primary tumors in the setting of unresectable metastases, the role of minimally invasive surgery, and how best to incorporate/sequence medical treatments. Low SBNET incidence, long event-times, and variability in disease burden, surgical technique, and institutional treatment preferences remain obstacles to conducting randomized surgical trials for SBNETs. With increasing referral of these patients to high-volume centers, cooperation between experienced SBNET clinicians should allow design of high-quality randomized trials to test new treatments and answer key questions.