ENETS Consensus Guidelines for the management of patients with digestive neuroendocrine neoplasms: colorectal neuroendocrine neoplasms

A small, well-differentiated rectal neuroendocrine tumor with multiple lymph node metastases: A case report

The incidence of rectal neuroendocrine tumor (NET), which is often diagnosed during routine surveillance endoscopy, is increasing. The majority of these tumors are small and asymptomatic, possessing benign features with favorable prognoses. At present, small rectal NETs without high-risk factors are typically treated by local resection, including endoscopic mucosal resection, endoscopic submucosal dissection, or transanal endoscopic microsurgery, with or without additional imaging follow-up by abdominal computed tomography or magnetic resonance imaging. The present study, however, describes a case of a small rectal NET without any known risk factors, which was accompanied by substantial locoregional lymph node metastasis, underscoring the importance of imaging studies for rectal NETs.

Colon and Rectal Neuroendocrine Tumors: Are They Really One Disease? A Single-Institution Experience over 15 Years

Colon and rectal neuroendocrine tumors (NETs) are often studied as one entity. Recent evidence suggests that worse outcomes are associated with colon compared with rectal NETs; direct comparisons are lacking. Our aim was to assess clinicopathologic, treatment, and survival differences between these diseases. All patients who underwent resection of colorectal NETs at one institution from 2000 to 2014 were included and analyzed. Of 29 patients, 12(41%) had colon and 17 (59%) had rectal NETs. Baseline demographics were similar between groups, although colon patients tended to be symptomatic at presentation (67% vs 44%, P = 0.41). Eighty-three per cent of colon patients underwent surgical resection, whereas 77 per cent of rectal patients underwent endoscopic or transanal resection ( P = 0.003). Colon patients had larger (3.4 cm vs 0.7 cm, P = 0.03), higher T-stage (T3/T4: 91% vs 14%, P = 0.003), higher grade tumors (42% vs 12%, P = 0.09) with more lymph nodes (58% vs 24%, P = 0.12) and lymphovascular invasion positivity (58% vs 24%, P = 0.32). Five-year disease-specific survival was 53% versus 80 per cent for colon and rectal patients, respectively ( P = 0.22). After excluding high-grade tumors, colon NETs were associated with lymphovascular invasion positivity (100% vs 17%, P = 0.05) and advanced T-stage (80% vs 8%, P = 0.01). Colon and rectal 5-year disease-specific survival was 67 versus 80 per cent ( P = 0.86). Colon and rectal NETs clinically seem to be distinct entities. Colon tumors have more aggressive clinicopathologic features, which may translate to worse outcomes. These differences in tumor biology may demand distinct management and should be further studied in a multi-institutional setting.

Neuroendocrine neoplasms of rectum: A management update

The estimated annual incidence of R-NENs is 1.04 per 100,000 persons although the real incidence may be underestimated, as not all R-NEN are systematically reported in registers. Also the prevalence has increased substantially, reflecting the rising incidence and indolent nature of R-NENs, showing the highest prevalence increase among all site of origin of NENs. The size of the tumor reveals the behavior of R-NENs where the risk for metastatic spread increases for lesions > 10 mm. Applying the WHO 2010 grading system to whole NENs originating in the gastroenteropancreatic system, R-NENs are classified as Well-Differentiated Neuroendocrine Tumors (WD-NET), which contain NET G1 and NET G2, and Poorly-Differentiated Carcinomas (PD-NEC) enclosing only G3 neoplasms for which the term carcinoma is applied. The treatment is endoscopic resection in most cases: conventional polypectomy or endoscopic mucosal resection (EMR) for smaller lesions or endoscopic submucosal resection with a ligation device (ESMR-L), cap-assisted EMR (EMR-C) and endoscopic submucosal dissection (ESD). However it is important to know when the endoscopic treatment is not enough, and surgical treatment is indicated, or when the latter could be unnecessary. For PD-NECs, it has recently been demonstrated that chemoradiotherapy is associated with a similar long-term survival to that obtained with surgery. As well, new targeted-agents chemotherapy may be indicated for metastatic WD-NETs.

Rectal and anal canal neuroendocrine tumours

Neuroendocrine tumors (NETs) are rare, representing 0.5% of all newly diagnosed malignancies. Rectal and anal canal (AC) NETs account for less than 1% of all rectal and AC cancers. Review our institutional experience on NET of the rectum and AC, with emphasis on demographic, histological and treatment features and oncologic outcomes. The study group was identified from the Portuguese Regional South Oncological Registry. From 2000 to 2014, 22 patients with rectal or AC NETs were treated at our institution. Medical records were retrospectively reviewed. There were 12 males (54.5%) and 10 females (45.5%) and the median age at diagnosis was 59.5 years. The majority had rectal NET (81.8%). All 4 patients with AC NETs had neuroendocrine carcinoid (NEC) tumors. Of the patients with rectal NETs, 3 had NEC and 15 had NET, mainly G1. Different approaches to treatment were made according to histological and staging features. After an average follow-up of 39.1 months, 16 patients were alive and only one with evidence of disease. The median time to progression was 12.4 months and the liver was the most frequent site of metastasis. The European and North American Neuroendocrine Societies offer guidelines for the treatment of rectal NETs. However, for AC NETs there are only small series and not prospective studies due to their rarity, hence the importance to report institutional experience. Our practice demonstrated that primary excisional treatment, regardless the histology, provides a favorable prognosis and long survival.

Identification of Phosphohistone H3 Cutoff Values Corresponding to Original WHO Grades but Distinguishable in Well-Differentiated Gastrointestinal Neuroendocrine Tumors

Mitotic counts in the World Health Organization (WHO) grading system have narrow cutoff values. True mitotic figures, however, are not always distinguishable from apoptotic bodies and darkly stained nuclei, complicating the ability of the WHO grading system to diagnose well-differentiated neuroendocrine tumors (NETs). The mitosis-specific marker phosphohistone H3 (PHH3) can identify true mitoses and grade tumors reliably. The aim of this study was to investigate the correspondence of tumor grades, as determined by PHH3 mitotic index (MI) and mitotic counts according to WHO criteria, and to determine the clinically relevant cutoffs of PHH3 MI in rectal and nonrectal gastrointestinal NETs. Mitotic counts correlated with both the Ki-67 labeling index and PHH3 MI, but the correlation with PHH3 MI was slightly higher. The PHH3 MI cutoff ≥4 correlated most closely with original WHO grades for both rectal NETs. A PHH3 MI cutoff ≥4, which could distinguish between G1 and G2 tumors, was associated with disease-free survival in patients with rectal NETs, whereas that cutoff value showed marginal significance for overall survival in patient with rectal NETs. In conclusion, the use of PHH3 ≥4 correlated most closely with original WHO grades.

Long-term Outcomes of Gastroenteropancreatic Neuroendocrine Tumors

OBJECTIVES

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare but have been increasing in incidence. Limited data on the long-term outcomes of patients with these tumors are available.

METHODS

In this study, we used population-based data from the National Cancer Institute to assess long-term disease-specific survival (DSS) of patients who have undergone surgery for nonmetastatic disease. All patients with NETs of the stomach, small intestine, colon, rectum, appendix, and pancreas diagnosed between 1988 and 2009 were identified from the Surveillance, Epidemiology and End Results registry. Staging was derived from Surveillance, Epidemiology and End Results data using the European Neuroendocrine Tumor Society guidelines. Cases with incomplete staging data were excluded, along with those with stage IV disease, or those who did not undergo surgical resection.

RESULTS

Kaplan-Meier analyses were constructed to determine DSS. Analyses were further stratified according to tumor site, stage at diagnosis, and tumor grade. Overall, 13,348 patients with GEP-NETs meeting the inclusion criteria were identified.

CONCLUSIONS

There were excellent outcomes for most GEP-NET patients, with a 20-year DSS of greater than 75% across all sites and stages. Pancreatic tumors had the worst outcomes, but DSS remains greater than 50% at 20 years.

Long-term Outcome of Small, Incidentally Detected Rectal Neuroendocrine Tumors Removed by Simple Excisional Biopsy Compared With the Advanced Endoscopic Resection During Screening Colonoscopy

BACKGROUND

Incidental, small rectal neuroendocrine tumors during colonoscopy screening are sometimes removed using biopsy forceps. Few studies have examined the clinical course of rectal neuroendocrine tumors removed by simple excisional biopsy.

OBJECTIVE

We investigated the long-term outcome of rectal neuroendocrine tumors removed by simple excisional biopsy compared with standard endoscopic resection.

DESIGN

This was a cohort study.

SETTINGS

This study was performed at a healthcare center in Korea.

PATIENTS

We enrolled patients with rectal neuroendocrine tumors detected during a screening colonoscopy between 2003 and 2015.

MAIN OUTCOME MEASURES

The clinical characteristics and long-term outcomes (overall survival and disease-free survival) of small neuroendocrine tumors <10 mm were compared between the simple excisional biopsy group and advanced endoscopic resection group.

RESULTS

In total, 166 patients were diagnosed with rectal neuroendocrine tumors (≤5 mm, n = 100; 6-9 mm, n = 50; 10-19 mm, n = 15; ≥20 mm, n = 1). Among the 150 patients with neuroendocrine tumors <10 mm, follow-up endoscopy was performed on 99 (59.6%). All of the tumors were confined to the mucosa or submucosa. Thirty-one and 68 patients were included in the simple excisional biopsy and advanced endoscopic resection groups. The overall follow-up duration was 6.5 years (range, 1.0-12.8 y). Neither overall nor disease-related death occurred. Two patients exhibited local recurrence (6.5%, at 8 and 11 y) in the simple excisional biopsy group and 1 patient (1.5%, at 7 y) in the advanced endoscopic resection group, resulting in no significant difference (p = 0.37). All of the recurrences were diagnosed >5 years from initial diagnosis and successfully treated endoscopically.

LIMITATIONS

More long-term data should be warranted.

CONCLUSIONS

The long-term outcome of small rectal neuroendocrine tumors <10 mm removed by simple excisional biopsy was excellent. Neither overall survival nor disease-free survival significantly differed between the simple excisional biopsy group and the advanced endoscopic resection group. Thus, simple excisional biopsy and long-term follow-up can be cautiously applied for small rectal neuroendocrine tumors in clinical practice. See Video Abstract at http://links.lww.com/DCR/A406.

Prognostic Factors for Locoregional Recurrence in Neuroendocrine Tumors of the Rectum

BACKGROUND

Optimal management of rectal neuroendocrine tumors is not yet well defined. Various pathologic factors, particularly tumor size, have been proposed as prognostic markers.

OBJECTIVE

We characterized sequential patients diagnosed with rectal neuroendocrine tumors in a population-based setting to determine whether tumor size and other pathologic markers could be useful in guiding locoregional management.

DESIGN

This study is a retrospective analysis of data from the British Columbia provincial cancer registry.

SETTINGS

The study was conducted at a tertiary care center.

PATIENTS

Sequential patients diagnosed with rectal neuroendocrine tumors between 1999 and 2011 were identified. Neuroendocrine tumors were classified as G1 and G2 tumors with a Ki-67 ≤20% and/or mitotic count ≤20 per high-power field.

MAIN OUTCOME MEASURES

Baseline clinicopathologic data including TNM staging, depth of invasion, tumor size, treatment modalities, and outcomes including survival data were measured.

RESULTS

Of 91 rectal neuroendocrine tumors, the median patient age was 58 years, and 35 were men. Median tumor size was 6 mm. Median length of follow-up was 58.1 months, with 3 patients presenting with stage IV disease. Treatment included local ablation (n = 5), local excision (n = 79), surgical resection (n = 4), and pelvic radiation (n = 1; T3N1 tumor). Final margin status was positive in 17 cases. Local relapse occurred in 8 cases and 1 relapse to bone 13 months after T3N1 tumor resection. Univariate analysis demonstrated an association between local relapse and Ki-67, mitotic count, grade, and lymphovascular invasion (p < 0.01). Larger tumor size was associated with decreased disease-free survival.

LIMITATIONS

Sample size was 91 patients in the whole provincial population over a 13-year time period because of the low incidence of rectal neuroendocrine tumors.

CONCLUSIONS

In this population-based cohort, rectal neuroendocrine tumors generally presented with small, early tumors and were treated with local excision or surgical resection without pelvic radiation. Pathologic markers play a role in risk stratification and prognostication. See Video Abstract at http://links.lww.com/DCR/A514.

Diagnosis and Management of Rectal Neuroendocrine Tumors

The incidence of rectal neuroendocrine tumors (NETs) has increased by almost ten-fold over the past 30 years. There has been a heightened awareness of the malignant potential of rectal NETs. Fortunately, many rectal NETs are discovered at earlier stages due to colon cancer screening programs. Endoscopic ultrasound is useful in assessing both residual tumor burden after retrospective diagnosis and tumor characteristics to help guide subsequent management. Current guidelines suggest endoscopic resection of rectal NETs ≤10 mm as a safe therapeutic option given their low risk of metastasis. Although a number of endoscopic interventions exist, the best technique for resection has not been identified. Endoscopic submucosal dissection (ESD) has high complete and en-bloc resection rates, but also an increased risk of complications including perforation. In addition, ESD is only performed at tertiary centers by experienced advanced endoscopists. Endoscopic mucosal resection has been shown to have variable complete resection rates, but modifications to the technique such as the addition of band ligation have improved outcomes. Prospective studies are needed to further compare the available endoscopic interventions, and to elucidate the most appropriate course of management of rectal NETs.

Management of Well-differentiated Gastroenteropancreatic Neuroendocrine Tumors (GEPNETs): A Review

PURPOSE

Neuroendocrine tumors (NETs) are heterogeneous tumors that arise from the neuroendocrine cells of the digestive tract and other organs, such as the lung, ovary, and thyroid glands. They can be well differentiated or poorly differentiated, and management of these tumors differs for each histologic subtype. We have performed a review of NETs and focused on management of well-differentiated gastroenteropancreatic neuroendocrine tumors (GEPNETs) and carcinoid syndrome.

METHODS

A PubMed search was performed to obtain articles on the management of well-differentiated NETs. Using the key words neuroendocrine tumors, carcinoid, pNET, octreotide, somatostatin analogues, and radiolabeled therapy, we reviewed Phase II and III trials that were published over the past 30 years. We also reviewed guidelines from the European Neuroendocrine Tumor Society, North America Neuroendocrine Tumor Society, and National Comprehensive Cancer Network in our search.

FINDINGS

NETs are usually slow-growing tumors that remain asymptomatic for a long duration and can be either nonfunctioning or functioning. Surgical resection is recommended for locoregional disease, impending obstruction, symptom control, and advanced disease. Nonsurgical treatment options include somatostatin analogues (SSAs), multikinase inhibitors, targeted therapy, chemotherapy, and radiolabeled SSAs. Carcinoid syndrome is mainly treated with SSAs.

IMPLICATIONS

Although GEPNETs are slow-growing tumors, most patients are diagnosed with metastatic disease, and therefore it is important that the management of each patient be discussed in a multidisciplinary setting to optimize the treatment strategy. Patients should be considered for clinical trials and refractory cases referred to a specialty center.

Efficacy of Precut Endoscopic Mucosal Resection for Treatment of Rectal Neuroendocrine Tumors

Background/Aims

Endoscopic resection is the first-line treatment for rectal neuroendocrine tumors (NETs) measuring <1 cm and those between 1 and 2 cm in size. However, conventional endoscopic resection cannot achieve complete resection in all cases. We aimed to analyze clinical outcomes of precut endoscopic mucosal resection (EMR-P) used for the management of rectal NET.

Methods

EMR-P was used to treat rectal NET in 72 patients at a single tertiary center between 2011 and 2015. Both, circumferential precutting and EMR were performed with the same snare device in all patients. Demographics, procedural details, and histopathological features were reviewed for all cases.

Results

Mean size of the tumor measured endoscopically was 6.8±2.8 mm. En bloc and complete resection was achieved in 71 (98.6%) and 67 patients (93.1%), respectively. The mean time required for resection was 9.0±5.6 min. Immediate and delayed bleeding developed in six (8.3%) and 4 patients (5.6%), respectively. Immediate bleeding observed during EMR-P was associated with the risk of delayed bleeding.

Conclusions

Both, the en bloc and complete resection rates of EMR-P in the treatment of rectal NETs using the same snare for precutting and EMR were noted to be high. The procedure was short and safe. EMR-P may be a good treatment choice for the management of rectal NETs.

Medical Therapy of Gastrointestinal Neuroendocrine Tumors

Intestinal neuroendocrine tumors (NETs) constitute a heterogeneous group with duodenal, small intestinal, colonic and rectal NETs. They constitute more than half of all NETs, with the highest frequencies in the rectum, small intestine, and colon. The tumor biology varies with the location of the primary tumor as well as with the grade and staging of the tumor. Small intestinal NETs usually present low proliferation and are treated in the first line with somatostatin analogs according to current guidelines. If progression occurs, one can add interferon alpha or change the treatment to everolimus. Peptide receptor radionuclide therapy (PRRT) with Lutetium¹⁷⁷-DOTATATE can be an option in the future after registration of the compound. Rectal tumors are usually small when they metastasize; they can be treated with somatostatin analogs but more so with PRRT, while another option is of course everolimus. Colonic NETs are more aggressive than the rest of intestinal NETs and will be treated with everolimus, sometimes in combination with somatostatin analogs based on positive scintigraphy. Another option is a cytotoxic agent such as streptozotocin plus 5-fluorouracil (5-FU) or temozolomide plus capecitabine. The most aggressive tumors, i.e. neuroendocrine carcinoma G3, are treated with a platin-based therapy plus etoposide; if they present with a lower proliferation, i.e. <50%, temozolomide plus capecitabine plus bevacizumab can also be attempted. Duodenal NETs are mostly treated similar to pancreatic NETs, either with cytotoxic agents, streptozotocin plus 5-FU, or temozolomide plus capecitabine, or with targeted agents such as everolimus.

Evolving role of the endoscopist in management of gastrointestinal neuroendocrine tumors

Neuroendocrine tumors (NETs) are uncommon gastrointestinal neoplasms but have been increasingly recognized over the past few decades. Luminal NETs originate from the submucosa of the gastrointestinal tract and careful endoscopic exam is a key for accurate diagnosis. Despite their reputation as indolent tumors with a good prognosis, some NETs may have aggressive features with associated poor long-term survival. Management of NETs requires full understanding of tumor size, depth of invasion, local lymphadenopathy status, and location within the gastrointestinal tract. Staging with endoscopic ultrasound or cross-sectional imaging is important for determining whether endoscopic treatment is feasible. In general, small superficial NETs can be managed by endoscopic mucosal resection and endoscopic submucosal dissection (ESD). In contrast, NETs larger than 2 cm are almost universally treated with surgical resection with lymphadenectomy. For those tumors between 11-20 mm in size, careful evaluation can identify which NETs may be managed with endoscopic resection. The increasing adoption of ESD may improve the results of endoscopic resection for luminal NETs. However, enthusiasm for endoscopic resection must be tempered with respect for the more definitive curative results afforded by surgical treatment with more advanced lesions.

结肠神经内分泌瘤G2一例个案报道并文献复习

神经内分泌瘤是一类起源于神经内分泌细胞, 发病率低且具有分子和生物学行为异质性的肿瘤. 现报道一例右半结肠神经内分泌瘤G2伴多发淋巴结转移患者, 以期对临床工作者有所帮助.

Is endoscopic ultrasonography essential for endoscopic resection of small rectal neuroendocrine tumors?

AIM

To evaluate the importance of endoscopic ultrasonography (EUS) for small (≤ 10 mm) rectal neuroendocrine tumor (NET) treatment.

METHODS

Patients in whom rectal NETs were diagnosed by endoscopic resection (ER) at the Pusan National University Yangsan Hospital between 2008 and 2014 were included in this study. A total of 120 small rectal NETs in 118 patients were included in this study. Histologic features and clinical outcomes were analyzed, and the findings of endoscopy, EUS and histology were compared.

RESULTS

The size measured by endoscopy was not significantly different from that measured by EUS and histology (r = 0.914 and r = 0.727 respectively). Accuracy for the depth of invasion was 92.5% with EUS. No patients showed invasion of the muscularis propria or metastasis to the regional lymph nodes. All rectal NETs were classified as grade 1 and demonstrated an L-cell phenotype. Mean follow-up duration was 407.54 ± 374.16 d. No patients had local or distant metastasis during the follow-up periods.

CONCLUSION

EUS is not essential for ER in the patient with small rectal NETs because of the prominent morphology and benign behavior.

Frequent Presence of Lymphovascular Invasion in Small Rectal Neuroendocrine Tumors on Immunohistochemical Analysis

Rectal neuroendocrine tumors (RNETs) have become common in recent years and are good candidates for endoscopic resection (ER). To achieve clear resection margins, more advanced techniques such as endoscopic submucosal dissection, endoscopic submucosal resection with a ligation device, and cap-assisted endoscopic mucosal resection are available for ER. After ER, lymphovascular invasion (LVI) is regarded as an important predictor of nodal metastasis. Previous studies have shown that small RNETs with LVI were uncommon (0-8.3%). However, using immunohistochemical analysis, a recent study revealed the frequent occurrence of LVI in small RNETs in a systematic manner (46.7%). There is a possibility that the actual detection rate of LVI in small RNETs is not always evaluated accurately because of the limited detection sensitivity of conventional hematoxylin-eosin staining. In addition, the correlation between LVI detected using immunohistochemical analysis and the development of metastasis remains unclear. Further prospective studies are required to clarify the role of LVI detected using immunohistochemical analysis.

Clinicopathological Features and Prognostic Factors of Colorectal Neuroendocrine Neoplasms

Background. Limited research is available regarding colorectal NENs and the prognostic factors remain controversial. Materials and Methods. A total of 68 patients with colorectal NENs were studied retrospectively. Clinical characteristics and prognosis between colonic and rectal NENs were compared. The Cox regression models were used to evaluate the predictive capacity. Results. Of the 68 colorectal NENs patients, 43 (63.2%) had rectal NENs, and 25 (36.8%) had colonic NENs. Compared with rectal NENs, colonic NENs more frequently exhibited larger tumor size (P < 0.0001) and distant metastasis (P < 0.0001). Colonic NENs had a worse prognosis (P = 0.027), with 5-year overall survival rates of 66.7% versus 88.1%. NET, NEC, and MANEC were noted in 61.8%, 23.5%, and 14.7% of patients, respectively. Multivariate analyses revealed that tumor location was not an independent prognostic factor (P = 0.081), but tumor size (P = 0.037) and pathological classification (P = 0.012) were independent prognostic factors. Conclusion. Significant differences exist between colonic and rectal NENs. Multivariate analysis indicated that tumor size and pathological classification were associated with prognosis. Tumor location was not an independent factor. The worse outcome of colonic NENs observed in clinical practice might be due not only to the biological differences, but also to larger tumor size in colonic NENs caused by the delayed diagnosis.

Rectal neuroendocrine neoplasia: a rare tumour

Colorectal neuroendocrine tumours are rare A 78 year old man with a history of hypertension, heart disease, pacemakers, prostate adenocarcinoma.On examination for rectal bleeding, a colonoscopy was performed and at 5 cm of the anal margin a 28 mm ulcerated neoformation was found.An echo-endoscopy revealed infiltration of the muscular layer with an area of loss in the cleavage plane loss and fraying of the perirectal fat infiltration suggestive of infiltration (T3). They no lymph nodes or metastasis were identified by CAT. Radiotherapy treatment is ruled out due to having had it previously on the prostate and a proctectomy was opted for with mesorectal resection and Hartmann intervention. The pathology report revealed a large cell neuroendocrine carcinoma with numerous implants in perirectal adipose tissue and lymph metastasis in 2 lymph nodes (pT4aN1b), positive for synaptophysin, chromogranin and CD 56 with proliferation index Ki-67 50%.

Recurrence 30 Years after Surgical Resection of a Localized Rectal Neuroendocrine Tumor

Localized small rectal neuroendocrine tumors (NETs) without any vascular involvement rarely metastasize, and their resection alone is considered curative. We herein report a case of localized rectal NET (10×8 mm) without vascular involvement. Although resected initially, it recurred as liver metastasis 30 years later. For rectal NETs smaller than 10 to 20 mm, surveillance for 12 months is considered sufficient. However, this case suggests that such tumors can recur even 30 years after curative resection. The interval of recurrence is the longest among reported cases.

Lymphovascular invasion in more than one-quarter of small rectal neuroendocrine tumors

AIM

To identify the frequency, clinicopathological risk factors, and prognostic significance of lymphovascular invasion (LVI) in endoscopically resected small rectal neuroendocrine tumors (NETs).

METHODS

Between June 2005 and December 2015, 104 cases of endoscopically resected small (≤ 1 cm) rectal NET specimens at Hallym University Sacred Heart Hospital in Korea were retrospectively evaluated. We compared the detected rate of LVI in small rectal NET specimens by two methods: hematoxylin and eosin (H&E) and ancillary immunohistochemical staining (D2-40 and Elastica van Gieson); in addition, LVI detection rate difference between endoscopic procedures were also evaluated. Patient characteristics, prognosis and endoscopic resection results were reviewed by medical charts.

RESULTS

We observed LVI rates of 25.0% and 27.9% through H&E and ancillary immunohistochemical staining. The concordance rate between H&E and ancillary studies was 81.7% for detection of LVI, which showed statistically strong agreement between two methods (κ = 0.531, P < 0.001). Two endoscopic methods were studied, including endoscopic submucosal resection with a ligation device and endoscopic submucosal dissection, and no statistically significant difference in the LVI detection rate was detected between the two (26.3% and 26.8%, P = 0.955). LVI was associated with large tumor size (> 5 mm, P = 0.007), tumor grade 2 (P = 0.006). Among those factors, tumor grade 2 was the only independent predictive factor for the presence of LVI (HR = 4.195, 95%CI: 1.321-12.692, P = 0.015). No recurrence was observed over 28.8 mo regardless of the presence of LVI.

CONCLUSION

LVI may be present in a high percentage of small rectal NETs, which may not be associated with short-term prognosis.

Short- and long-term outcomes of endoscopic resection of rectal neuroendocrine tumours: analyses according to the WHO 2010 classification

OBJECTIVE

Although the World Health Organisation (WHO) defined a novel classification of gastroenteropancreatic neuroendocrine tumours (NETs) in 2010, indications for endoscopic resection of rectal NETs in the guidelines were based on evidence accumulated for carcinoid tumours defined by a previous classification. This study was designed to clarify indications for endoscopic resection of rectal NETs corresponding to the new WHO classifications.

MATERIAL AND METHODS

One hundred-seventy rectal NETs resected endoscopically from April 2001 to March 2012 were histologically re-classified according to the WHO 2010 criteria. The clinicopathological features of these lesions were analysed, and the short- and long-term outcomes of endoscopic resection were evaluated.

RESULTS

Of the 170 rectal NETs, 166 were histopathologically diagnosed as NET G1 and four as NET G2. Thirty-eight tumours (22.4%) were positive for lymphovascular invasion, a percentage higher than expected. Although the curative resection rate was low (65.3%), en bloc (98.8%) and complete (85.9%) resection rates were high. Modified endoscopic mucosal resection (88.0%) and endoscopic submucosal dissection (92.2%) resulted in significantly higher complete resection rates than conventional endoscopic mucosal resection (36.4%). No patient experienced tumour recurrence, despite the low curative resection rate.

CONCLUSION

Despite the low curative resection rate, prognosis after endoscopic resection of rectal NETs was excellent. Prospective large-scale, long-term studies are required to determine whether NET G2 and tumours >1 cm should be included in the indication for endoscopic resection and whether tumours with lymphovascular invasion can be followed up without additional surgery.

Enhanced detection of lymphovascular invasion in small rectal neuroendocrine tumors using D2-40 and Elastica van Gieson immunohistochemical analysis

Rectal neuroendocrine tumor (RNET) lymphovascular invasion (LVI) is regarded as an important predictor of nodal metastasis after endoscopic resection (ER). However, little is known about the frequency of immunohistochemical detection of LVI in RNETs. This study was performed to establish the actual detection of LVI rate in RNETs ≤10 mm and to evaluate associated clinical outcomes. We retrospectively reviewed the records for 98 consecutive patients treated by ER with a total of 102 RNETs ≤10 mm. Tissue sections were labeled with hematoxylin–eosin (HE) stain, the D2‐40 monoclonal antibody to evaluate lymphatic invasion, and Elastica van Gieson (EVG) stain to detect venous invasion. LVI detection rate by HE versus immunohistochemical analysis was compared. Follow‐up findings and clinical outcomes were also evaluated for 91 patients who were followed for ≥12 months. Lymphatic and venous invasion were detected using HE staining alone in 6.9% and 3.9% of patients, respectively, whereas they were detected using D2‐40 and EVG staining in 20.6% and 47.1% of the patients, respectively. Thus, the LVI detection frequency using D2‐40 and EVG staining (56.9%) was significantly higher than with HE (8.8%). Two out of seven patients who required additional surgery had regional lymph node metastases. However, among the 84 patients who were followed up without surgery, no distant metastases or recurrences were detected. Compared with HE staining, immunohistochemical analysis significantly increased the frequency of LVI detection in RNETs ≤10 mm. However, the clinical impact of LVIs detected using immunohistochemical analysis remains unclear. Clarification of the actual role of LVI using immunohistochemical analysis requires a patient long‐term follow‐up and outcomes.

Transanal endoscopic microsurgery as optimal option in treatment of rare rectal lesions: A single centre experience

AIM

To analyze the outcomes of transanal endoscopic microsurgery (TEM) in the treatment of rare rectal condition like mesenchymal tumors, condylomas, endometriosis and melanoma.

METHODS

We retrospectively reviewed a twenty-three years database. Fifty-two patients were enrolled in this study. The lesions were considered suitable for TEM if they were within 20 cm from the anus. All of them underwent an accurate preoperative workup consisting in clinical examination, total colonoscopy with biopsies, endoscopic ultrasonography, and pelvic computerized tomography or pelvic magnetic resonance imaging. Operative time, intraoperative complications, rate of conversion, tumor size, postoperative morbidity, mortality, the length of hospital stay, local and distant recurrence were analyzed.

RESULTS

Among the 1328 patients treated by TEM in our department, the 52 patients with rectal abnormalities other than adenoma or adenocarcinoma represented 4.4%. There were 30 males (57.7%) and 22 females (42.3%). Mean age was 55 years (median = 60, range = 24-78). This series included 14 (26.9%) gastrointestinal stromal tumors, 21 neuroendocrine tumors (40.4%), 1 ganglioneuroma (1.9%), 2 solitary ulcers in the rectum (3.8%), 6 cases of rectal endometriosis (11.5%), 6 cases of rectal condylomatosis (11.5%) and 2 rectal melanomas (3.8%). Mean lesion diameter was 2.7 cm (median: 4, range: 0.4-8). Mean distance from the anal verge was 9.5 cm (median: 10, range: 4-15). One patient operated for rectal melanoma developed distant metastases and died two years after the operation. We experienced 2 local recurrences (3.8%) with an overall survival equal to 97.6% (95%CI: 95%-99%) at the end of follow-up and a disease free survival of 98% (95%CI: 96%-99%).

CONCLUSION

We could conclude that TEM is an important therapeutical option for rectal rare conditions.

Long-Term Clinical Outcomes of Rectal Neuroendocrine Tumors According to the Pathologic Status After Initial Endoscopic Resection: A KASID Multicenter Study

OBJECTIVES

With advances in diagnostic endoscopy, the detection of rectal neuroendocrine tumors (NETs) has increased. However, clinical outcomes, especially after endoscopic treatment, are still unclear. The aim of this study was to determine the long-term clinical outcomes of endoscopically resected rectal NETs according to the pathologic status after initial resection.

METHODS

In this large, multicenter, retrospective cohort study, we analyzed the medical records of patients who underwent endoscopic resection of rectal NETs and were followed for ≥24 months at 16 university hospitals. The outcomes of interest were local or distant recurrence and metachronous lesions.

RESULTS

On the pathologic assessment of 407 patients, the resection margin status was positive in 76 (18.7%) and indeterminate in 72 (17.7%) patients. Patients whose rectal NETs were diagnosed or suspected as NETs before resection showed a much higher complete resection rate than those whose tumors were resected as polyps and then diagnosed (P<0.001). Fourteen patients received salvage treatment at 1.9±2.8 months after initial treatment. During a median follow-up period of 45.0 months, local recurrence occurred in 3 (0.74%) patients, but there was no recurrence in the lymph nodes or distant organs. Metachronous rectal NETs were diagnosed in 3 (0.74%) patients. According to the pathologic status after initial resection, local recurrence and metachronous lesions occurred in 1 (0.4%) and 2 (0.8%) patients, respectively, in the pathologic tumor-free group, whereas they occurred in 2 (1.4%) and 1 (0.7%) patients, respectively, in the indeterminate group.

CONCLUSIONS

Considering the long-term prognosis including that for recurrences or metachronous lesions, endoscopic resection is an efficient and a safe modality for the treatment of rectal NETs. This treatment may result in favorable clinical outcomes in patients with tumors of indeterminate pathology, as well as in pathologic tumor-free cases after initial resection.

Review article: the investigation and management of rectal neuroendocrine tumours

BACKGROUND

Rectal neuroendocrine tumours (NETs) are increasingly identified at endoscopy possibly as a result of bowel cancer screening programmes.

AIM

To present a review of the literature to aid clinicians in the diagnosis and management of rectal neuroendocrine tumours.

METHODS

A literature search was conducted through MEDLINE using search terms: rectal, rectum, carcinoid, NET, therapy, endoscopy, mucosal resection, submucosal dissection. Relevant articles were identified through manual review with reference lists reviewed for additional articles.

RESULTS

The incidence of rectal neuroendocrine tumours is approximately 1 per 100 000 population per year with the majority (80-90%) being <1 cm and localised to the submucosa. Metastatic disease is infrequent (<20%) with risk factors including size, atypical appearance, grade and depth of invasion. The primary resection modality influences complete resection rates and the need for secondary therapy. A thorough pre-resection diagnostic work up is required for lesions that are at higher risk of invasion and metastasis. Device-assisted endoscopic mucosal resection and endoscopic submucosal dissection are used to resect localised rectal neuroendocrine tumours <2 cm. Transanal surgery is also used to resect localised 1-2 cm rectal neuroendocrine tumours. Oncological surgical resection is used for rectal neuroendocrine tumours that are >2 cm or with invasion and regional disease. The treatment of advanced disease is multimodal.

CONCLUSIONS

The long-term tumour biology of small rectal neuroendocrine tumours remains unclear. There is uncertain impact from bowel cancer screening programmes on rectal neuroendocrine tumour incidence, morbidity and mortality. Referral to neuroendocrine tumour centres for patients with locally advanced disease or metastatic disease is recommended.

Mixed Adenoneuroendocrine Carcinoma Causing Colonic Intussusception

Colonic intussusception is a rare cause of intestinal obstruction in adults and is caused by a malignant lesion in about 70% of cases. Early diagnosis and treatment are essential. We present a 64-year-old male patient with right colonic intussusception caused by a mixed adenoneuroendocrine carcinoma (MANEC), presenting as a giant pedunculated polyp (54 mm of largest diameter). The patient underwent right colectomy with primary anastomosis and adjuvant chemotherapy. The diagnosis of intussusception of the colon in adults is difficult because of its rarity and nonspecific clinical presentation. In this case, the cause was a rare histological type malignant tumor (MANEC).

Endoscopic Resection for Small Rectal Neuroendocrine Tumors: Comparison of Endoscopic Submucosal Resection with Band Ligation and Endoscopic Submucosal Dissection

Background and Aims. There is no consensus so far regarding the optimal endoscopic method for treatment of small rectal neuroendocrine tumor (NET). The aim of this study was to compare treatment efficacy, safety, and procedure time between endoscopic submucosal resection with band ligation (ESMR-L) and endoscopic submucosal dissection (ESD). Methods. We conducted a prospective study of patients who visited Inha University Hospital for endoscopic resection of rectal NET (≦10 mm). Pathological complete resection rate, procedure time, and complications were evaluated. Results. A total of 77 patients were treated by ESMR-L (n = 53) or ESD (n = 24). En bloc resection was achieved in all patients. A significantly higher pathological complete resection rate was observed in the ESMR-L group (53/53, 100%) than in the ESD group (13/24, 54.2%) (P = 0.000). The procedure time of ESD (17.9 ± 9.1 min) was significantly longer compared to that of ESMR-L (5.3 ± 2.8 min) (P = 0.000). Conclusions. Considering the clinical efficacy, technical difficulty, and procedure time, the ESMR-L method should be considered as the first-line therapy for the small rectal NET (≤10 mm). ESD should be left as a second-line treatment for the fibrotic lesion which could not be removed using the ESMR-L method.

Gastroenteropancreatic Well-Differentiated Grade 3 Neuroendocrine Tumors: Review and Position Statement

: In 2010, the World Health Organization (WHO) classification of neuroendocrine neoplasms was reviewed and validated the crucial role of the proliferative rate. According to the WHO classification 2010, gastroenteropancreatic neuroendocrine neoplasms are classified as well-differentiated neuroendocrine tumors (NETs) of grade 1 or 2 in up to 84%, or poorly differentiated neuroendocrine carcinomas in 6%-8%. Neuroendocrine carcinomas are of grade G. Recently, a proportion of neuroendocrine tumors presenting a number of mitoses or a Ki-67 index higher than 20% and a well-differentiated morphology have been identified, calling for a new category, well-differentiated grade 3 NET (NET G-3). Studies that have reported the characteristics of neuroendocrine neoplasms have identified more well-differentiated NET G-3 than neuroendocrine carcinomas. The main localizations of NET G-3 are the pancreas, stomach, and colon. Treatment for NET G-3 is not standardized and is balanced between G-1/2 neuroendocrine tumor and neuroendocrine carcinoma treatments. In nonmetastatic neuroendocrine tumors, the European and American guidelines recommended a surgical resection for localized neuroendocrine neoplasm, irrespective of the tumor grading. In NET G-3, chemotherapy is the benchmark if the main treatment goal is reduction of the tumor mass, particularly if it would allow a secondary surgery. In the present work, we review the epidemiology and make recommendations for the management of NET G-3.

IMPLICATIONS FOR PRACTICE

Neuroendocrine tumors presenting a number of mitoses or a Ki-67 index higher than 20% and a well-differentiated morphology have been identified and named well-differentiated grade 3 neuroendocrine tumors (NET G-3). The main localizations of NET G-3 are the pancreas, stomach, and colon. The prognosis is worse than that for NET G-2. In nonmetastatic NET G-3, surgery appeared to be the first option. The chemotherapy regimen in pancreatic NET G-3 should be in line with that implemented in NET G-1/2 when the Ki-67 index is below 55% and should be in line with that implemented for neuroendocrine carcinoma when Ki-67 is above 55%.

Prognostic factors for disease relapse in patients with neuroendocrine tumours who underwent curative surgery

AIM

Surgery is the only modality of cure in patients diagnosed with neuroendocrine tumours (NETs). The aim of this study was to identify prognostic factors associated with disease relapse in patients with NETs treated by potentially-curative surgery.

METHODS

Sequential patients registered in The Christie European NET Society (ENETS) Centre of Excellence, with grade (G)1 or G2 NETs who had undergone curative surgery (February 2002-June 2014) were included. Investigated prognostic factors for relapse were: age, gender, TNM stage, tumour-localisation, functionality, genetic predisposition, presence of multiple NETs, second malignancy, grade (Ki-67-based), presence of vascular and/or perineural invasion, necrosis, surgical margin (R0/R1), Eastern Cooperative Oncology Group performance status and Adult Comorbidity Evaluation co-morbidity score.

RESULTS

One hundred and eighty-eight patients were identified [median age of 60 years (range 16-89)]. With a median follow-up of 2.6 years, 43 relapses occurred. The estimated median relapse-free survival (RFS) for the entire cohort was 8.0 years (95% confidence interval [CI] 5.9-10.0 years). In univariate analysis, primary NET location (p = 0.01), ENETS T-(HR-1.4; 95%-CI 1.0-2.0, p = 0.026), N-(HR-2.0, 95%-CI 1.1-3.9, p = 0.026) and M-stage (HR-2.6, 95%-CI 1.1-6.3, p = 0.052), grade (Ki-67%-based) (HR-2.5; 95%-CI 1.4-4.7; p = 0.003) and perineural invasion (HR-2.1; 95%-CI 1.1-3.9; p = 0.029) were prognostic for relapse. Factors remaining significant after multivariable analysis were tumour size (HR-1.67; 95%-CI 1.04-2.70; p = 0.03), nodal involvement (HR-2.61; 95%-CI 1.17-5.83; p = 0.013) and Ki-67 at the time of diagnosis (HR-1.93; 95%-CI 1.24-3.0; p = 0.002).

CONCLUSION

Size of tumour, lymph node involvement and Ki-67 were independent prognostic factors for relapse after potentially curative surgery in NET.

Diagnosis and management of gastrointestinal neuroendocrine tumors: An evidence-based Canadian consensus

The majority of neuroendocrine tumors originate in the digestive system and incidence is increasing within Canada and globally. Due to rapidly evolving evidence related to diagnosis and clinical management, updated guidance on the diagnosis and treatment of gastrointestinal neuroendocrine tumors (GI-NETs) are of clinical importance. Well-differentiated GI-NETs may exhibit indolent clinical behavior and are often metastatic at diagnosis. Some NET patients will develop secretory disease requiring symptom control to optimize quality of life and clinical outcomes. Optimal management of GI-NETs is in a multidisciplinary environment and is multimodal, requiring collaboration between medical, surgical, imaging and pathology specialties. Clinical application of advances in pathological classification and diagnostic technologies, along with evolving surgical, radiotherapeutic and medical therapies are critical to the advancement of patient care. We performed a systematic literature search to update our last set of published guidelines (2010) and identified new level 1 evidence for novel therapies, including telotristat etiprate (TELESTAR), lanreotide (CLARINET), everolimus (RADIANT-2; RADIANT-4) and peptide receptor radionuclide therapy (PRRT; NETTER-1). Integrating these data with the clinical knowledge of 16 multi-disciplinary experts, we devised consensus recommendations to guide state of the art clinical management of GI-NETs.

[Neoplasms of the disseminated neuroendocrine cell system of the gastrointestinal tract]

The classification of neuroendocrine neoplasms (NEN) of the gastrointestinal tract and also the pancreas is based on the World Health Organization (WHO) classification from 2010, the site-related TNM stage classification and the clinicopathological characterization. This allows a classification of NEN that is adapted to the individual patient, is of high prognostic relevance and serves the needs of an adequate treatment. This article summarizes the current knowledge on the clinical pathology of gastrointestinal NEN, in order to enable a rapid diagnostic orientation.

[Rectal neuroendocrine tumors: surgical therapy]

The incidence of rectal neuroendocrine tumors (NET) has increased in recent years. Most of these neoplasms are asymptomatic and are diagnosed by colonoscopy screening, which could be one of the reasons for the increasing occurrence. As less than 1 % of rectal NET produce serotonin they are practically never discovered due to a carcinoid syndrome. The current guidelines of the European (ENETS) and North American (NANETS) Neuroendocrine Tumor Societies support clinicians with useful diagnostic and treatment algorithms. The most important criteria for therapy are tumor size and histopathological risk factors for metastases. For well-differentiated rectal neuroendocrine neoplasms < 1 cm, local endoscopic or surgical excision is recommended. Due to the lack of evidence tumors sized 1-2 cm represent a grey area for prognosis and treatment. All NET > 1.5 cm must be excised by radical surgery as low anterior rectal resection or abdominoperineal extirpation with total mesorectal excision (TME). Resectable liver and lung metastases of well-differentiated NETs should be surgically treated with curative intent.

Pathologic Features of Primary Colon, Rectal, and Anal Malignancies

In the United States, colorectal cancer is the third most commonly diagnosed cancer in both men and women, as well as the third leading cause of cancer deaths (Colorectal cancer facts & figures 2014–2016, 2014 [2]). Worldwide, colorectal cancer is the fourth leading cause of death and causes almost 700,000 deaths each year (Cancer: fact sheet No. 297, 2015 [55]). This chapter discusses the clinical and pathologic features of the spectrum of epithelial, hematolymphoid, and mesenchymal malignant tumors of the colon, rectum, appendix, and anus.

Neuroendocrine tumours - Medical therapy: Biological

Somatostatin analogues (SSA) are well established antisecretory drugs that have been used as first line treatment for symptomatic control in hormonally active neuroendocrine tumours (NET) for three decades. Both available depot formulations of SSA, long-acting repeatable (LAR) octreotide and lanreotide autogel, seem similarly effective and well tolerated, although comparative trials in NET have not been performed. The importance of SSA as antiproliferative treatment has been increasingly recognized during recent years. Two placebo-controlled trials demonstrated significant prolongation of progression free survival under SSA treatment. However, objective response as assessed by imaging is rare. Interferon-α (IFNα) also has antisecretory and antiproliferative efficacy in NET. Due to the less favourable toxicity profile it mainly has a role as add-on option in the refractory setting, especially in carcinoid syndrome patients. Further studies are needed to evaluate the antiproliferative efficacy of the multiligand SSA pasireotide and the role of pegylated IFNα.

Excellent prognosis following endoscopic resection of patients with rectal neuroendocrine tumors despite the frequent presence of lymphovascular invasion

BACKGROUND

Endoscopic resection (ER) has been increasingly used for the treatment of rectal neuroendocrine tumors (NETs); however, only limited data are available on its long-term outcomes. This study analyzed the long-term outcomes of rectal NETs treated by ER and characterized potential risk factors for metastasis in these cases, with emphasis on lymphovascular invasion.

METHODS

We retrospectively analyzed the clinicopathological features and outcomes of 86 patients with 90 rectal NETs who had been treated by ER. Lymphovascular invasion was reevaluated using elastic-staining and double-staining immunohistochemistry.

RESULTS

En bloc resection with tumor-free margins was achieved in 87 lesions (96.7%). The median tumor size was 5 mm (range 2-13), and all the lesions were confined to the submucosal layer. The Ki-67 index was less than 3% in all the lesions, which were therefore classified as NET G1. Elastic-staining and double-staining immunohistochemistry revealed the presence of lymphatic and venous invasion in 23 (25.6%) and 35 lesions (36.7%), respectively. Collectively, lymphatic and/or vascular invasion was identified in 42 lesions (46.7%). All cases were followed up without additional surgery, and no metastasis or recurrence was detected during the median follow-up period of 67.5 months.

CONCLUSIONS

This study showed an excellent long-term prognosis following ER of patients with rectal NETs, confirming that ER is a valid treatment option for small rectal NETs. The present study also revealed highly prevalent lymphovascular invasion even in minute rectal NETs; this observation raises a question regarding its significance as a risk factor for metastasis.

Dilemmas in Endoscopic Management of Rectal Neuroendocrine Tumors: A Case-Based Discussion

Rectal neuroendocrine tumors are uncommon neoplasms that historically were regarded as having an indolent course. Due to the widespread use of screening colonoscopy neuroendocrine tumors of the rectum are identified with increasing frequency. More recent literature has suggested that rectal neuroendocrine tumors may progress in a more malignant fashion than previously believed. In this case-based discussion we present management dilemmas, analyze current guidelines, and highlight the role of endoscopic ultrasound, endoscopic resection, and surgery.

Advantage of endoscopic mucosal resection with a cap for rectal neuroendocrine tumors

AIM: To compare the outcomes of endoscopic mucosal resection with a cap (EMR-C) with those of endoscopic submucosal dissection (ESD) for the resection of rectal neuroendocrine tumors.

METHODS: One hundred and sixteen lesions in 114 patients with rectal neuroendocrine tumor (NET) resected with EMR-C or ESD were included in the study. This study was performed at Pusan National University Yangsan Hospital between July 2009 and August 2014. We analyzed endoscopic complete resection rate, pathologic complete resection rate, procedure time, and adverse events in the EMR-C (n = 65) and ESD (n = 51) groups. We also performed a subgroup analysis by tumor size.

RESULTS: Mean tumor size was 4.62 ± 1.66 mm in the EMR-C group and 7.73 ± 3.14 mm in the ESD group (P < 0.001). Endoscopic complete resection rate was 100% in both groups. Histologic complete resection rate was significantly greater in the EMR-C group (92.3%) than in the ESD group (78.4%) (P = 0.042). Mean procedure time was significantly longer in the ESD group (14.43 ± 7.26 min) than in the EMR-C group (3.83 ± 1.17 min) (P < 0.001). Rates of histologic complete resection without complication were similar for tumor diameter ≤ 5 mm (EMR-C, 96%; ESD, 100%, P = 0.472) as well as in cases of 5 mm < tumor diameter ≤ 10 mm (EMR-C, 80%; ESD, 71.0%, P = 0.524).

CONCLUSION: EMR-C may be simple, faster, and more effective than ESD in removing rectal NETs and may be preferable for resection of small rectal NETs.

PET tracers for somatostatin receptor imaging of neuroendocrine tumors: current status and review of the literature

Neuroendocrine tumors have shown rising incidence mainly due to higher clinical awareness and better diagnostic tools over the last 30 years. Functional imaging of neuroendocrine tumors with PET tracers is an evolving field that is continuously refining the affinity of new tracers in the search for the perfect neuroendocrine tumor imaging tracer. (68)Ga-labeled tracers coupled to synthetic somatostatin analogs with differences in affinity for the five somatostatin receptor subtypes are now widely applied in Europe. Comparison of sensitivity between the most used tracers - (68)Ga-DOTA-Tyr3-octreotide, (68)Ga-DOTA-Tyr3-octreotate and (68)Ga-DOTA-l-Nal3-octreotide - shows little difference and expertise on the specific tracer used, and knowledge regarding physiological uptake might be more important than in vitro-proven differences in affinity. Using isotopes such as (18)F or (64)Cu might improve these PET tracers further.