Transanal endoscopic surgery is a recommended full-thickness resection technique for the treatment of rectal neuroendocrine tumors. We aimed to compare the efficacy, safety and follow-up of patients with rectal neuroendocrine tumors treated with transanal endoscopic microsurgery in the primary setting and as salvage therapy after non-radical endoscopic polypectomy.

A retrospective analysis of a 10-year database of patients treated with transanal endoscopic microsurgery was performed. The procedure-related measures, including duration of the procedure, adverse events, and patient-related measures, including age, gender, tumor size, grading, and length of follow-up, were obtained. We compared the primary TEM group with the salvage group.

In total, 30 patients with rectal neuroendocrine tumors were included in the study; 13 of them received primary treatment and 17 salvage therapy of the scar. Patients receiving primary treatment were significantly older (60.5 vs. 51.7 years). There were no significant differences in patient gender, tumor size and grading, length of follow-up, hospital stay or procedure time. The R0 resection rate was 92.3% in the primary treatment group. Adverse events were mild or managed with endoscopic treatment. Follow-up was slightly but not significantly longer in the primary treatment group and showed no recurrences in both groups of patients.

Transanal endoscopic microsurgery is safe and effective for both primary and salvage treatment of rectal neuroendocrine tumors.

The aim of the article was to systematically evaluate the clinical efficacy and safety of transanal endoscopic microsurgery (TEM) and endoscopic submucosal dissection (ESD) in the treatment of rectal tumors.

Control studies were conducted on cases included in the electronic databases Medline, Embase, Cochrane Library, and CNKI. Patients with colorectal tumors were included in the TEM and ESD groups for treatment, with the main indicators being R0 resection rate, postoperative perforation and bleeding incidence, and tumor recurrence rate. The meta-analysis was carried out using RevMan 5.3 software.

A total of 10 studies were included, with 736 patients. The analysis showed that for the recurrence rate in the TEM group compared to ESD, OR = 1.23, 95% CI = 0.56-2.72, p = 0.60; for the R0 resection rate between the TEM group and ESD group, OR = 1.35, 95% CI = 0.82-2.22, p = 0.24; for the incidence of perforation in the TEM and ESD groups, OR = 0.59, 95% CI = 0.25-1.40, p = 0.23. The inter-group comparison of these three items was statistically significant. Compared with the ESD group, the hospitalization time and the incidence of bleeding of the TEM group were both lower, with SD = 0.48, 95% CI = 0.26-0.69, p < 0.001 and OR = 0.35, 95% CI = 0.13-0.92, p = 0.03. The differences were statistically significant.

Both TEM and ESD endoscopic treatment techniques can achieve a higher R0 resection rate and lower risk of tumor recurrence in the treatment of colorectal tumors. However, TEM may have higher surgical safety than ESD technology, and can shorten postoperative hospitalization time and lower postoperative bleeding rate.

Rectal neuroendocrine neoplasms (r-NENs) are considered among the most frequent digestive NENs, together with small bowel NENs. Their incidence has increased over the past few years, and this is probably due to the widespread use of endoscopic screening for colorectal cancer and the advanced endoscopic procedures available nowadays. According to the current European Neuroendocrine Tumor Society (ENETS) guidelines, well-differentiated r-NENs smaller than 10 mm should be endoscopically removed in view of their low risk of local and distant invasion. R-NENs larger than 20 mm are candidates for surgical resection because of their high risk of distant spreading and the involvement of the muscularis propria. There is an area of uncertainty regarding tumors between 10 and 20 mm, in which the metastatic risk is intermediate and the endoscopic treatment can be challenging. Once removed, the indications for surveillance are scarce and poorly codified by international guidelines, therefore in this paper, a possible algorithm is proposed.

Transanal endoscopic microsurgery (TEM) and Transanal endoscopic operation (TEO) have been initially described for local excision of rectal adenomas and selected cases of rectal carcinomas. In the past decade, however, several new indications raised, and others could raise in the future. The aim of this review was to evaluate, both in the literature and in our personal experience, the use of TEM and TEO for nonconventional applications, different from rectal tumors.

We conducted a systematic review of published papers and we selected articles reporting patients who underwent endoscopic surgery for other medical reason than polyp cancer resection, with TEM or TEO. PubMed, MEDLINE, EMBASE and bibliographies of the selected studies were searched for articles in English published up to May 2020 to identify all relevant articles. We excluded articles reporting TEM and TEO used for classical indications. We finally report our experience of non-conventional use of TEO in 5 patients with different diseases.

The research revealed 800 papers and among them we selected 52 articles for a total of 697 patients. Of all patients, only 52 had intraoperative or postoperative complications, with only 10 patients requiring major surgery.

Our study suggest that TEM and TEO may be valid alternatives to traditional surgery in situations other than its classical indication. These findings can positively impact on the care of patients, who could benefit from less invasive surgical procedures associated with lower morbidity.

Owing to an increased number of colonoscopy screenings, the incidence of diagnosed rectal neuroendocrine tumors (NETs) has also increased. Tumor size is one of the most frequently regarded factors when selecting treatment; however, it may not be the determinant prognostic variable. We aimed to evaluate oncological outcomes according to the treatment modality based on the size of rectal NETs.

A retrospective analysis was performed on patients who were treated for rectal NETs between March 2000 and January 2016 at the Asan Medical Center, Seoul, Korea. Patients who underwent endoscopic removal, local surgical excision, and radical resection were included. The primary outcome was recurrence-free survival (RFS). Data were specified and analyzed following the 2019 World Health Organization classification (WHO).

A total of 644 patients were categorized under three groups according to the treatment modality used: endoscopic removal (n = 567), surgical local excision (n = 56), and radical resection (n = 21). Of a total of 35 recurrences, 27 were local, whereas eight were distant. The RFS rate did not differ significantly between the treatment groups in the same tumor-size group ([Formula: see text]1 cm group: P = .636, 1-2 cm group: P = .160). For T1 tumors, RFS rate was not different between local excision and radical resection ([Formula: see text]1 cm group: P = .452, 1-2 cm group: P = .700). Depth of invasion, a high Ki-67 index, and margin involvement were confirmed as independent risk factors for recurrence. Among patients treated with endoscopic removal, endoscopic biopsy was a significant factor for worse RFS (P < .001), while tumor size did not affect the RFS.

The current guideline recommends treatment options according to tumor size. However, more oncologically important prognostic factors include muscularis propria invasion and a higher Ki-67 index.

Rectal neuroendocrine tumors (NETs) are rare, with an incidence of 0.17%, but they represent 12% to 27% of all NETs and 20% of gastrointestinal NETs. Although rectal NETs are uncommon tumors, their incidence has increased over the past few years, and this is probably due to the improvement in detection rates made by advanced endoscopic procedures. The biological behavior of rectal NETs may be different: factors predicting the risk of metastases have been identified, such as size and grade of differentiation. The tendency for metastatic diffusion generally depends on the tumor size, muscular and lymphovascular infiltration, and histopathological differentiation. According to the current European Neuroendocrine Tumor Society (ENETS) guidelines, tumors that are smaller than 10 mm and well differentiated are thought to have a low risk of lymphovascular invasion, and they should be completely removed endoscopically. Rectal NETs larger than 20 mm have a higher risk of involvement of muscularis propria and high metastatic risk and are candidates for surgical resection. There is controversy over rectal NETs of intermediate size, 10-19 mm, where the metastatic risk is considered to be 10-15%: assessment of tumors endoscopically and by endoanal ultrasound should guide treatment in these cases towards endoscopic, transanal, or surgical resection.

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) with favorable pathological and clinical features may be considered as indolent lesions, and therefore be amenable to conservative management. According to the primary tumor site, different non-aggressive approaches, based on endoscopic resection or simple active surveillance, can be proposed to selected patients fulfilling specific criteria. Tumor size, Ki67 proliferative index and depth of invasion are markers that can be used in order to identify these subjects. Patients with type I gastric NENs <1 cm as well as those with non-ampullary duodenal NENs <1 cm with no associated syndrome can be safely managed by endoscopic resection. On the other hand, an active surveillance approach is preferred over surgery for patients with asymptomatic, non-functioning pancreatic NENs ≤2 cm without dilation of the main pancreatic duct or bile duct. As far as NENs of the appendix are concerned, appendectomy should be considered as curative when a R0 resection has been achieved in the presence of a tumor ≤1.5 cm, graded as G1 and without lymphovascular invasion. Finally, G1 rectal NENs ≤1 cm without invasion of the muscular layer can be safely treated by endoscopic resection. Therefore, surgeons should be aware of the existence of indolent GEP-NENs, in order to avoid unnecessary operations with associated postoperative complications.

Both endoscopic techniques and transanal surgery are viable options that allow organ preservation for early rectal neoplasms. Whilst endoscopic approaches are less invasive and carry less morbidity, it is unclear whether they are as oncologically effective.

To compare endoscopic techniques with transanal surgery in the management of early rectal neoplasms.

A systematic literature search was performed for randomised and observational studies comparing these techniques. The pre-specified main outcomes measured were en bloc and R0 resection rates and recurrence. Pair-wise meta-analysis was performed.

This review included 1044 patients. Transanal surgery had increased R0 resection rates (odds ratio (OR) 2.66; 95% CI 1.64; 4.31; p < 0.001) versus endoscopic management. The latter was associated with higher rates of incomplete resection (OR 2.25; 95% CI 1.14, 4.46; p = 0.02) and further intervention (OR 1.78; 95% CI 1.09, 2.88; p = 0.02). There was no difference in the rates of late recurrence (OR 1.01; 95% CI 0.53, 1.91; p = 0.99) or further major surgery (OR 0.87; 95% CI 0.39, 1.94; p = 0.73) between the groups. Endoscopic treatment was associated with a shorter operating time (weighted mean difference (WMD) - 12.08; 95% CI - 18.97, - 5.19; p < 0.001) and LOS (WMD - 1.94; 95% CI - 2.43, - 1.44; p < 0.001), as well as lower rates of urinary retention post-operatively (OR 0.12; 95% CI 0.02, 0.63; p = 0.01).

Endoscopic techniques should be favoured in the setting of benign early rectal neoplasms given their decreased morbidity and increased cost-effectiveness. However, where malignancy is suspected transanal surgery should be the preferred option given the superior R0 resection rate.

The aim of our study was to explore the value of the 8th edition TNM staging system on evaluating the prognosis of colorectal carcinoid. Colorectal carcinoid patients between 1988 and 2015 were selected in the Surveillance, Epidemiology, and End Results Program (SEER) database for analysis. About 4286 patients with colorectal carcinoid tumors were identified, of which were carcinoid tumor NOS (n = 1726), neuroendocrine carcinoma (NEC) (n = 1346) and other carcinoid tumor (OCT) (n = 591). Worsening 10-year CSS rates with increasing N status, M status, and SEER historic stage were demonstrated across all three above groups (all P < .05). In carcinoid tumor NOS, significant differences in CSS were found with increasing combined 8th AJCC stages (P < .001), except for that between stage II and stage III (10-year CSS rate: 82.6% vs 84.3%, P = .68). While combined 8th TNM stage in NEC and OTC exhibited greater separations in CSS despite on-going overlaps between groups. For carcinoid tumor NOS, stage II (HR = 3.37; 95% CI: 0.97-11.76), and stage III (HR = 2.09; 95% CI: 0.51-8.66) conferred no significant difference in CSS compared with stage I, while stage IV had an increasing HR of 5.09 (95% CI: 1.08-24.08). Although combined 8th AJCC stage had a good ability to distinguish 10-year CSS of patients with NEC or OCT, detailed 8th AJCC stage did not seem to be applicable. Detailed 8th AJCC categories of advanced stages in all the three groups conferred increased HRs with overlapping CIs. However, in the early and middle status, HRs did not increase with the increase of stages, or there was no difference in HRs between adjacent stages. Combined 8th TNM stage was not practical for judging the survival outcomes of colorectal carcinoid tumor NOS, especially in patients with stages II and III, but it provided useful prognostic information for NEC and OCT. However, for all carcinoid tumors, the prognostic values of detailed 8th AJCC stage were not enough accurate in the clinic. More optimized staging methods should be developed and validated in the future.

Rectal neuroendocrine tumors (RNET) are rare tumors but their prevalence is constantly increasing due to a prolonged survival and rising incidence related to a growing number of colonoscopies and improved knowledge. Their main prognostic determinant is tumor stage. While most RNET are localized, their management should be tailored depending on the presence or absence of the factors predictive of lymph-node metastases including tumor size, endoscopic aspect, T stage, grade and lymphovascular invasion. Endoscopic ultrasonography is the most relevant technique for locoregional assessment. Low-risk RNET can be treated using advanced endoscopic resection techniques or transanal endoscopic microsurgery, in expert centers because they require technicity and experience. Conversely, radical surgery with lymphadenectomy should be proposed in the presence of any pejorative factor. The long-term evolution of RNET remains to be specified, and prospective studies should be conducted in order to determine the relevance of the current management strategies.

Purpose: To date, there is not enough evidence concerning the optimal treatment strategy for early rectal carcinoids, we conducted a meta-analysis in order to determine the feasible local treatment for these selected patients. Methods: We searched the studies from the PubMed, Cochrane database, Medline, Ovid, SpringerLink, PMC and Embase between January 2007 and April 2017. Studies of local surgical excision compared with endoscopic resection for rectal carcinoids less than 20mm without adverse features were included. Data were analyzed by using Stata SE 12.0. Results: Seven studies were included in this meta-analysis, with a total of 1056 patients. The data showed that local surgical excision was associated with higher complete resection rate than that of endoscopic resection (OR 5.837, 95%CI 2.048 to 16.632, P=0.001) but consuming longer procedural time (SMD 1.757, 95% CI 1.263 to 2.251, P=0.000). Additionally, incidences of recurrence and en bloc resection rate were comparable between two kinds of resections. The difference of post-operative complications remained unclear. Conclusions: For rectal carcinoids sized 20mm or smaller without adverse features, endoscopic resection might be an efficient treatment, which achieved a comparable oncological safety as local surgical excision.