Nodal metastases in small rectal neuroendocrine tumours

Risk factors for lateral pelvic lymph node metastasis in patients with rectal neuroendocrine tumors: a systematic review and meta-analysis

Background and objective

Lateral pelvic lymph node (LPLN) metastasis is one of the prominent reasons for local recurrence in patients with rectal neuroendocrine tumors (RNETs). The evaluation criteria of lateral lymph node metastasis for patients and the indications and value of lateral pelvic lymph node dissection (LPLD) have been controversial. Total mesorectal excision (TME), a conventional surgical treatment for RNETs, excluding lateral lymph nodes, may be one of the reasons for postoperative local recurrence. This study aimed to analyze the risk factors for LPLN metastasis in patients with RNETs in order to guide surgical methods.

Methods

We searched relevant databases (PubMed, Embase, Medline, Cochrane Library, and Web of Science) for articles published between 1 January 2000 and 1 April 2024 to evaluate the risk factors for LPLN metastasis in patients with RNETs in this meta-analysis.

Results

A total of seven articles with 433 patients were included in this study. The overall results showed that a WHO grade > G1, tumor invasion of the muscularis propria or deeper, lymphovascular invasion (LVI), mesorectal lymph node metastasis (MLNM), and distant metastasis (M1) were significant risk factors for LPLN metastasis in patients with RNETs (P <0.05).

Conclusion

This study identified key risk factors for LPLN metastasis in patients with RNETs, providing guidance for treatment strategies. A comprehensive evaluation of these risk factors and imaging findings is recommended to tailor personalized treatment strategies that optimize survival outcomes and improve quality of life.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024581891.

An Update on the Management of Rectal Neuroendocrine Neoplasms

OPINION STATEMENT

Rectal neuroendocrine neoplasms (NENs) are increasing in incidence. Most lesions are low grade, well-differentiated neuroendocrine tumours with good long term outcomes. However there is metastatic potential and resection offers the only option for a cure and in most cases should be offered to reduce the risk of metastases. Careful staging of rectal NENs should be performed prior to consideration of resection in order to ensure the appropriate technique is chosen, and reduce the risk of incomplete resection. Resection can be endoscopic or surgical, and selecting the appropriate resection technique relies on tumour characteristics such as size, grade, invasion into the muscularis propria, presence of lymph node involvement or of distal metastases. Some patients may require systemic therapies which may involve somatostatin analogues (SSAs), everolimus, tyrosine kinase inhibitors (TKIs), chemotherapy or peptide receptor radionuclide therapy (PRRT). Due the rarity of these tumours, much of the evidence is based on retrospective reviews or smaller cohort studies. This article is an update of the current evidence available to guide management.

Outcome of Endoscopic Resection of Rectal Neuroendocrine Tumors ≤ 10 mm

BACKGROUND AND AIM

Guidelines suggest endoscopic resection for rectal neuroendocrine tumors (rNETs) < 10 mm, but the most appropriate resection technique is unclear. In real-life clinical practice, the endoscopic removal of unrecognized rNETs can take place with "simple" techniques and without preliminary staging. The aim of the current study is to report our own experience at a referral center for both neuroendocrine neoplasms and endoscopy.

METHODS

Retrospective analyses of polypectomies were performed at the Humanitas Research Hospital for rNETs (already diagnosed or previously unrecognized).

RESULTS

A total of 19 patients were included, with a median lesion size of 5 mm (range 3-10 mm). Only five lesions were suspected as NETs before removal and underwent endoscopic ultrasound (EUS) before resection, being removed with advanced endoscopic techniques. Unsuspected rNETs were removed by cold polypectomy in eleven cases, EMR in two, and biopsy forceps in one. When described, the margins were negative in four cases, positive in four (R1), and indeterminate in one. The median follow-up was 40 months. A 10 mm polypoid lesion removed with cold snare polypectomy (G2 R1) needed subsequent surgery. Eighteen patients underwent EUS after a median time of 6.5 months from resection. The EUS identified local recurrence after 14 months in a 7 mm polypoid lesion removed with cold snare polypectomy (G1 R1); the lesion was treated with cap-assisted EMR. For all the other lesions, the follow-up was negative.

CONCLUSIONS

When rNETs are improperly removed without prior staging, caution must be exercised. The data from our cohort suggest that even if inappropriate resection had happened, patients may be safely managed with early EUS evaluation.

The role of endoscopic ultrasonography for diagnosis of residual rectal neuroendocrine tumor

BACKGROUND

Endoscopic ultrasonography (EUS) is useful for assessing the depth and regional lymph node involvement in rectal neuroendocrine tumors (NETs). However, evidence regarding the effectiveness of EUS in identifying residual lesions in patients with incompletely resected NET is limited. We aimed to evaluate the efficacy of EUS in identifying residual rectal NETs and the clinical outcomes of salvage endoscopic treatment.

METHODS

We retrospectively reviewed the records of patients who were transferred to Chosun University Hospital and received salvage treatment for incompletely resected rectal NETs between January 2012 and October 2021.

RESULTS

This study included 68 incompletely resected rectal NET, of which 59 were margin-positive and 9 were margin-indeterminate. EUS detection (odds ratio (OR), 8.44; 95% confidence interval (CI), 1.18-41.35) and visual detection (OR, 7.00; 95% CI, 1.50-47.48) were associated with residual lesion in patients with incompletely resected NET. EUS detection of residual lesions showed a sensitivity of 94%, specificity of 71%, positive predictive value of 88%, negative predictive value of 83%, and accuracy of 87%. All patients underwent salvage treatment with band-ligation endoscopic mucosal resection (58.8%) and endoscopic submucosal dissection (41.2%). Residual NETs were diagnosed in 47 of 68 patients (69.1%), and no recurrence was noted during the follow-up period of 51.8 ± 22.9 months.

CONCLUSIONS

EUS is a more sensitive method than visual detection for evaluating residual rectal NETs. Salvage endoscopic treatment for incompletely resected NETs is safe and effective.

Impact of grade on workup of rectal neuroendocrine tumors: a retrospective cohort study : Grade impact on workup of rectal NETs

BACKGROUND

Rectal neuroendocrine tumors (RNETs) are often discovered on screening colonoscopy. Indications for staging and definitive resection are inconsistent in current guidelines. We evaluated the role of grade in guiding staging and procedural decision-making.

METHODS

Patients with biopsy confirmed RNETs between 2004 and 2015 were reviewed. Baseline characteristics, staging investigations (biochemical and imaging), and endoscopic/surgical treatment were recorded. Associations between grade, preoperative staging, interventions, and survival were determined using Fisher-Freeman-Halton Exact, log-rank, and Kaplan-Meier analysis.

RESULTS

Amongst 139 patients with RNETs, 9% were aged ≥ 75 years and 44% female. Tumor grade was: 73% grade 1 (G1), 18%, grade 2 (G2) and 9% grade 3 (G3). Staging investigations were performed in 52% of patients. All serum chromogranin A and 97% of 24-hour urine 5-hydroxyindoleacetic acid tests were normal. The large majority of staging computed tomography (CT) scans were negative (76%) with subgroup analysis showing no G1 patients with CT identified distant disease compared with 38% of G2 and 50% of G3 patients (p < 0.001). G1 patients were more likely to achieve R0/R1 resections compared to G2 (95% vs. 50%, p < 0.001) and G1 patients had significantly better 5-year overall survival (G1: 98%, G2: 67%, G3: 10%, p < 0.001).

CONCLUSION

Tumor grade is important in preoperative workup and surgical decision-making. Biochemical staging may be omitted but staging CT should be considered for patients with grade ≥ 2 lesions. Anatomic resections should be considered for patients with grade 2 disease.

Systematic Resection of the Visible Scar After Incomplete Endoscopic Resection of Rectal Neuroendocrine Tumors

INTRODUCTION

When initial resection of rectal neuroendocrine tumors (r-NETs) is not R0, persistence of local residue could lead to disease recurrence. This study aimed to evaluate the interest of systematic resection of non-R0 r-NET scars.

METHODS

Retrospective analysis of all the consecutive endoscopic revisions and resections of the scar after non-R0 resections of r-NETs.

RESULTS

A total of 100 patients were included. Salvage endoscopic procedure using endoscopic submucosal dissection or endoscopic full-thickness resection showed an R0 rate of near 100%. Residual r-NET was found in 43% of cases.

DISCUSSION

In case of non-R0 resected r-NET, systematic scar resection by endoscopic full-thickness resection or endoscopic submucosal dissection seems necessary.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for colorectal neuroendocrine tumours

This ENETS guidance paper, developed by a multidisciplinary working group, provides an update on the previous colorectal guidance paper in a different format. Guided by key clinical questions practical advice on the diagnosis and management of neuroendocrine tumours (NET) of the caecum, colon, and rectum is provided. Although covered in one guidance paper colorectal NET comprises a heterogeneous group of neoplasms. The most common rectal NET are often small G1 tumours that can be treated by adequate endoscopic resection techniques. Evidence from prospective clinical trials on the treatment of metastatic colorectal NET is limited and discussion of patients in experienced multidisciplinary tumour boards strongly recommended. Neuroendocrine carcinomas (NEC) and mixed neuroendocrine non-neuroendocrine neoplasms (MiNEN) are discussed in a separate guidance paper.

Optimising Outcomes and Surveillance Strategies of Rectal Neuroendocrine Neoplasms

Rectal neuroendocrine neoplasms are increasing in incidence, in part due to increased endoscopic procedures being performed for bowel cancer screening. Whilst most of these lesions are low-grade well-differentiated neuroendocrine tumours, they can have a varied clinical behaviour. Frequently, these lesions are incorrectly characterised at endoscopy and, therefore, incompletely excised using standard polypectomy techniques. Furthermore, some cases are not fully staged prior to or post resection. In this article we discuss the endoscopic and surgical options available to improve the likelihood of achieving an R0 resection and the staging procedures that should be used in these NETs. We also review factors that may suggest a higher risk of nodal involvement or recurrence. This information may help determine whether endoscopic or surgical resection techniques should be considered. In cases of R1 resection we discuss the management options available and the long-term surveillance options and when these should be offered to patients.

Gastroenteropancreatic Neuroendocrine Tumors

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are the most common type of neuroendocrine tumors and are being increasingly identified in clinical practice. The diagnosis, staging, management, and surveillance of GEP-NETs rely heavily on endoscopy, and consequently, it is important for gastroenterologists to have a solid understanding of these tumors. This article reviews the presentation, diagnosis, and management of both localized and advanced GEP-NETs, with increased emphasis on the role of endoscopy, to enable gastroenterologists and other practitioners to have the necessary tools for the care of patients with these tumors.

Prognosis of incompletely resected small rectal neuroendocrine tumor using endoscope without additional treatment

BACKGROUND

In recent years, the incidence of rectal neuroendocrine tumors (NET)s has markedly increased due to the widespread use of screening colonoscopy. However, many patients are referred from local clinics after undergoing conventional endoscopic mucosal resection (EMR) for polyps without perceived NET, with a pathological report of incomplete resection. We evaluated the prognosis of incompletely resected small rectal NET without additional endoscopic resection for small rectal NET less than 10 mm in diameter present within the submucosal layer showing good prognosis, due to its rare metastatic potential.

METHODS

We retrospectively reviewed patients from 2008 to 2018 at a single center who had had small rectal NET (located in the rectum from the anal verge to 20 cm in proximity) and had undergone 'incomplete resection' using endoscopy with a positive deep margin or with a very small safe deep margin (< 100 um). A small rectal NET was defined as a tumor ≤ 10 mm in diameter, without lymph node nor distant metastasis, and with low grade (G1) according to the WHO grading system.

RESULTS

Of 267 patients who were diagnosed with small rectal NET, 77 were diagnosed with incomplete resection or possible remnant NET. Of those, 55 patients (55/77, 71.4%) were referred from local clinics post EMR diagnosed as polyps. The rate of histologically incomplete resection was highest in endoscopic submucosal dissection (11/21, 52.4%) and lowest in surgical resection (0/9, 0%), while endoscopic submucosal resection with band ligation showed an incomplete resection rate of 4.4% (5/113). After exclusion of 36 patients, namely 21 patients had undergone additional surgical (n = 6) or endoscopic (n = 15) resection and 25 patients who were lost during the follow-up period of 2 years, 31 patients had undergone surveillance with endoscopic evaluation or either a biopsy or radiological evaluation for distant metastasis during a median follow-up duration of 2 years. None of the incompletely resected small rectal NET patients showed local or distant metastasis.

CONCLUSION

Incomplete resection of small rectal NET with G1 grade has a good prognosis without additional treatment.