Rectal carcinoids are on the rise: early detection by screening endoscopy

Risk factors for residual tumors in histologically incompletely resected rectal neuroendocrine tumors

BACKGROUND

Rectal neuroendocrine tumors (r-NETs) are often misidentified as polyps, leading to inappropriate endoscopic treatment and incomplete resection.

AIMS

This study investigated the occurrence and risk factors of residual r-NETs following salvage local resection (SLR) after incomplete resection.

METHODS

The medical records of 95 patients who underwent SLR for histologically incompletely resected (R1/Rx-resected) r-NETs referred from other hospitals between January 2020 and August 2023 were analyzed.

RESULTS

The residual r-NET rate was 48.4 % (46/95), varying according to the primary resection method: cold forceps polypectomy (CFP), 70.0 % (21/30); conventional polypectomy or endoscopic mucosal resection (EMR), 41.7 % (25/60); and modified EMR or endoscopic submucosal dissection, 0 % (0/5). The residual r-NET rate was 65.7 % for endoscopically incomplete primary resection versus 0 % for endoscopically complete primary resection. Upon multivariate analysis, endoscopically suspected remnant tumors before SLR (odds ratio [OR], 15.56; 95 % confidence interval [CI], 2.94-82.35, p = 0.002) and the use of CFP for primary resection (OR, 3.60; 95 % CI, 1.02-14.52, p = 0.043) were associated with residual r-NETs after SLR.

CONCLUSION

Salvage resection should be considered for R1/Rx-resected r-NET cases with risk factors for residual tumors to lower the likelihood of recurrence.

Incidence of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs): An updated systematic review of population-based reports from 2010 to 2023

There is a general perception that the incidence of neuroendocrine neoplasms (NENs) has been increasing. Nevertheless, reports of actual population-based studies are scarce, and pertinent data from some geographical regions still need to be available. In this systematic literature review of population-based studies, we aimed to evaluate the available data to provide updated figures on the incidence of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs). Guided by the PRISMA 2020 statement reporting items for systematic reviews, this study conducted a systematic search using Ovid in the bibliographic databases Embase, Medline, and Web of Science Core Collection. Only incidence-reporting studies were included. In total, 847 articles were identified, and through a strict evaluation process using predefined inclusion and exclusion criteria, we found 19 papers that reported the general incidence of GEP-NENs from all sites. In addition, we considered another 15 papers that focused on the epidemiologic aspects of single-organ studies. While the incidence rates of GEP-NEN vary across similar countries, the general incidence of GEP-NEN has been increasing worldwide in recent decades. The incidence of GEP-NENs has increased worldwide over the last two decades, and reliable figures from new regions add to this pattern. Nevertheless, variations in the classification, grading, and reporting of GEP-NENs in various studies make direct comparisons difficult.

Endoscopic resection of rectal neuroendocrine tumors: zero disease-related deaths during a 10-year follow-up period

BACKGROUND

Gastrointestinal neuroendocrine tumors (GI-NETs) are slow-growing tumors with the potential for malignancy that originate from neuroendocrine cells. Therefore, early diagnosis and treatment of GI-NETs are necessary to prevent metastasis. The widespread use of colonoscopy, which allows early detection of rectal neuroendocrine tumors (rNETs) that are small enough to be treated endoscopically, has resulted in an increasing rate of endoscopic resection of rNETs. However, whether the long-term prognosis of endoscopically resected rNETs is favorable has not yet been determined. This study aimed to assess whether endoscopically resected rNETs affect the long-term prognosis of patients.

METHODS

We retrospectively reviewed the medical records of 163 consecutive patients with rNETs who underwent endoscopic resection at 11 hospitals in Japan between 1999 and 2012. The primary analysis focused on 47 patients with 51 rNETs who underwent ≥ 10 years of follow-up. The secondary analysis focused on patients who underwent less than 10 years of follow-up.

RESULTS

The median follow-up period of patients included in the primary analysis was 12.3 years (range, 10-19.1 years). The median lesion size was 5 mm (range, 2-12). Three lesions were treated using conventional endoscopic mucosal resection (EMR). Twenty-nine lesions were treated using modified EMR. Nineteen lesions were treated using endoscopic submucosal dissection. The R1 resection rate and lymphovascular invasion rate were 15.7% and 25.5%, respectively. The curative resection (CR) rate and non-CR rate were 66.7% and 33.3%, respectively. Two patients with lesions treated with non-CR underwent radical surgery. None of the 47 patients experienced lesion recurrence during the 10-year follow-up period. Two patients whose lesions were treated with CR died of other diseases.

CONCLUSIONS

Death attributable to rNETs did not occur among patients who underwent at least 10 years of follow-up after endoscopic resection.

Comparison of endoscopic submucosal dissection and modified endoscopic mucosal resection for rectal neuroendocrine tumors

Although some studies have compared the treatment outcomes between modified endoscopic mucosal resection (m-EMR) and endoscopic submucosal dissection (ESD) for rectal neuroendocrine tumors (NETs), the results are based on the experience of experts from a single high-volume center. This multicenter study aimed to compare the outcomes between m-EMR and ESD for rectal NETs, with emphasis on the operator's level. Data of patients with rectal NETs treated using m-EMR or ESD at seven institutions that included general hospitals in Japan were retrospectively reviewed. Patients treated using m-EMR and those treated using ESD were matched for age, sex, lesion size, lesion location, and operator level through propensity score matching. The treatment outcomes were compared between the two groups. In total 304 patients (m-EMR = 178, ESD = 126) were included, with 218 in the matched groups (m-EMR = 109, ESD = 109). The R0 resection rate was not significantly different between the two groups (90.0% vs. 82.3%, P = .221). However, the procedural time was significantly shorter for the m-EMR group than that for the ESD group (6 vs. 26 min, P < .001). No significant difference in adverse events was observed between the two groups (postprocedure bleeding rate: 5.5% vs. 2.8%, P = .335; perforation rate: 0.9% vs. 0.9%, P = 1.00). Subgroup analysis revealed that the R0 resection rate for the trainees was significantly higher in the m-EMR group than in the ESD group (87.9% vs. 64.5%, P = .017). m-EMR is the preferred technique for the treatment of rectal NETs and should be considered, particularly for the trainees.

Metachronous Liver Metastasis during Long-term Follow-up after Endoscopic Submucosal Dissection of a Small Rectal Neuroendocrine Neoplasm

A 67-year-old woman underwent a screening colonoscopy, which revealed a 7-mm rectal subepithelial lesion. Endoscopic submucosal dissection (ESD) confirmed a grade 1 rectal neuroendocrine neoplasm (NEN), and no further treatment was administered. One year after ESD, she was diagnosed with lung cancer, which recurred 4 years later and required chemotherapy. Nine years after ESD, multiple liver metastases from the rectal NEN were found, which were well controlled with radiofrequency ablation. The patient died 13 years after ESD due to the progression of lung cancer. This case highlights the need for long-term follow-up in patients with small rectal NENs treated with endoscopic resection.

Lateral pelvic lymph nodes dissection of rectal neuroendocrine neoplasms: A prospective case-series and literature review

BACKGROUND

Rectal neuroendocrine neoplasms are relatively rare. Patients with rectal neuroendocrine neoplasms undergoing radical surgery have a higher rate of lymph node metastases. Robust evidence on the status of lateral pelvic lymph node metastases and the role of lateral pelvic lymph node dissection in those patients is lacking. This case-series study aimed to explore and address these issues.

METHODS

This single-center, prospective case series consecutively enrolled patients with biopsy-proven rectal neuroendocrine neoplasms in a tertiary referral hospital between June 2022 and January 2024. All eligible patients underwent laparoscopic total mesorectal excision surgery and bilateral lateral pelvic lymph node dissection under general anesthesia. The clinicopathologic features, surgical outcomes, and postoperative complications were presented. The last follow-up was conducted in March 2024.

RESULTS

A total of 11 patients with rectal neuroendocrine neoplasms-3 female and 8 male-were enrolled. The average age was 60.0 years (range, 53.5-65.5 years), and the median tumor size was 2.0 cm (range, 1.6-2.5 cm). Tumors invaded the muscularis propria in 7 patients. There were 3 cases of neuroendocrine tumor G1, 6 cases of neuroendocrine tumor G2, and 2 cases of neuroendocrine carcinoma. Among these patients, 11 (100.0%) had lymph node metastases, and 6 (54.5%) had lateral pelvic lymph node metastases. In addition, in 2 patients, only lateral pelvic lymph node metastases were observed, without involvement of the mesenteric lymph nodes. Five patients had tumors located on the left wall of the rectum, and only left-sided lateral pelvic lymph node metastases were observed. The other patient had both sides of lateral pelvic lymph node metastases due to circumferential growth of the tumor around the rectum. Anal preservation was achieved in all patients. The median operating time was 235.0 minutes (range, 210.5-335.5 minutes), and the median estimated blood loss was 50.0 mL (range, 45.0-75.0 mL). Two patients experienced postoperative dysuria and recovered spontaneously within 2-4 months after surgery.

CONCLUSION

On the basis of a prospective case series, we demonstrate, for the first time, the lateral pelvic lymph node metastasis status in patients with rectal neuroendocrine neoplasms requiring radical total mesorectal excision surgery. Simultaneous bilateral lateral pelvic lymph node dissection may be a feasible and beneficial procedure for preventing local recurrence in these patients due to the lack of definitive neoadjuvant or adjuvant therapy options.

Clinical significance of positive resection margin for patients with rectal neuroendocrine tumors within 20 mm following initial endoscopic resection: A multi-center study

BACKGROUND

The incidence of rectal neuroendocrine tumors (RNETs) has witnessed a significant surge, with a notable proportion being amenable to endoscopic removal. However, the clinical significance of positive resection margin for RNETs patients following endoscopic resection remain unknown, resulting in a lack of consensus regarding the appropriateness of implementing salvage treatment.

METHODS

In this large, multicenter, retrospective cohort study, we analyzed the medical records of individuals who underwent endoscopic resection for RNETs and classified them into two groups: the positive resection margin and the negative resection margin group. The overall survival (OS) and disease-free survival (DFS) were compared among two group. The independent variables were identified using univariate and multivariate logistic regression analyses to predict positive resection margin. Then, the model was established to predict the patients with positive resection margin using multivariate logistic regression.

RESULTS

181 RNETs patients (34.3 %) represented positive margin after endoscopic resection. Following a median follow-up period of 72 months, tumor recurrence manifested in 12 out of 527 patients (2.2 %) and the presence of positive resection margin was associated with worse DFS. Independent factors correlating with positive resection margin included endoscopic resection method choice, RNETs located in the low rectum, NLR >4.44 and tumor size exceeding 14.89 mm. A prediction model was therefore established with high predictive accuracy and excellent clinical applicability determined by calibration curves and DCA curve. Among RNETs patients with positive margin following endoscopic resection, implementing salvage treatment was beneficial for improving DFS and salvage endoscopic resection offer equal efficiency compared with salvage radical resection.

CONCLUSIONS

Positive resection margin following endoscopic resection may indicate negative prognosis. Salvage treatment can improve the prognosis of RNETs patients with positive resection margin. Notably, salvage local resection exhibited similar efficacy compared with radical surgery in term of survival benefit.

Optimization of endoscopic treatment strategies for R0 resection of rectal neuroendocrine tumors smaller than 10 mm

BACKGROUND

The optimal histologically complete (R0) resection methods of endoscopy for rectal neuroendocrine tumor (NET) ≤ 10 mm remains controversial. We aimed to assess the optimal endoscopic treatments for NETs.

METHODS

The retrospective enrolled patients (n = 208) with rectal NETs were divided into 3 subsets according to pathological tumor size: 2 - 3 mm, 4 - 5 mm, and 6 - 10 mm NETs. Factors associated with R0 resection according to different endoscopic treatments (accidental diagnostic biopsy by cold forceps, endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD)) and tumor size were investigated. All patients underwent follow-up and no local recurrence or metastasis were identified.

RESULTS

A total of 208 patients were enrolled. In patients with 2 - 3 mm NETs, the R0 resection rate was 100.0 % for biopsy, EMR, and ESD. The R0 resection rate for biopsy of 4 - 5 mm and 6 - 10 mm NETs was 34.3 % and 0.0 % respectively, which was inferior to the EMR/ESD rate (4 - 5mm: p < 0.001; 6 - 10 mm: p < 0.001: respectively). For patients with ≤ 10 mm NETs, EMR and ESD had a comparable en bloc (p = 0.082) and R0 resection rates (p = 0.651).

CONCLUSION

Accidental diagnostic biopsy by cold forceps could be considered as the possible treatment for 2 - 3 mm rectal NETs. And for patients with ≤ 10 mm rectal NETs, both EMR and ESD might be sufficient.

Clinical outcomes after endoscopic resection and the risk of lymph node metastasis in rectal neuroendocrine tumors: a single-center retrospective study

BACKGROUND AND AIM

The incidence of rectal neuroendocrine tumors (R-NETs) has increased in recent years. However, the predictors of lymph node (LN) metastasis and clinical outcomes, particularly following endoscopic treatment, remain unclear. Our study aims to elucidate the potential risk factors for LN metastasis and the clinical outcomes of patients undergoing endoscopic resection in R-NETs.

METHODS

A total of 128 patients with R-NETs were retrospectively identified from a single center between June 2012 and December 2021. Risk factors for LN metastasis in R-NETs were analyzed using multivariate analysis. Additionally, the clinical outcomes of endoscopic resections in patients with R-NETs were assessed.

RESULTS

In our study, 128 patients with R-NETs were retrospectively analyzed. The risk factors for LN metastasis determined by multivariate analysis were tumor size and patient age at diagnosis. Among the 111 patients treated with endoscopic resection and with tumor margin records available, 92 underwent endoscopic submucosal dissection (ESD) and 19 underwent conventional endoscopic mucosal resection (EMR). There was no significant difference between the two groups regarding the positive rates of basal tumor margin and lateral tumor margin. Furthermore, 64 patients who underwent endoscopic resection for R-NETs were successfully followed up (range, 1.64-76.71 months), during which only one patient developed local recurrence.

CONCLUSION

Tumor size and age at diagnosis were predictors for LN metastasis of R-NETs. Both ESD and EMR are alternative techniques with a favorable prognosis for R-NETs, even in cases with positive resection margins. However, due to the relatively small number of patients undergoing EMR and missing data in follow-up protocols, definitive conclusions require further large-scale studies.

Comparison of endoscopic resection therapies for rectal neuroendocrine tumors

AIMS

This study was to evaluate and compare the efficacy and safety of endoscopic mucosal resection (EMR), clip-and-snare assisted endoscopic mucosal resection (CS-EMR), and endoscopic submucosal dissection (ESD) for the endoscopic resection of rectal NETs.

MATERIAL AND METHODS

A retrospective analysis was performed on 47 patients with rectal NETs who underwent endoscopic treatment in The Second Affiliated Hospital of Soochow University. Manifestations of clinic pathological characteristics, complications, procedure time and hospitalization costs were studied.

RESULTS

The complete resection rates with CS-EMR and ESD were significantly higher than those with EMR (CS-EMR vs. EMR, p = 0.038; ESD vs. EMR, p = 0.04), but no significant difference was found between the CS-EMR and ESD groups (p = 0.383). The lateral margin was less distant in the CS-EMR group than in the ESD group and there was no difference with regard to vertical margin (lateral margin distance, 1500 ± 3125 vs.3000 ± 3000 μm; vertical margin distance, 400 ± 275 vs.500 ± 500 μm). Compared to ESD, CS-EMR required less operation time (p < 0.01) and money (p < 0.01) and reduced the length of hospital stays (p < 0.01).

CONCLUSIONS

The CS-EMR technique is more effective and efficient than EMR for small rectal NETs. In addition, CS-EMR reduces procedure time, duration of post-procedure hospitalization and decreases patients' cost compared to ESD while ensuring sufficient vertical margin distances.

Risk of metastasis and survival in patients undergoing different treatment strategies with T1 colonic neuroendocrine tumors

PURPOSE

The efficacy and safety of local excision (LE) for small (< 1‒2 cm) colonic neuroendocrine tumors (NETs) is controversial due to the higher metastasis risk when compared with rectal NETs. The study aimed to evaluate the metastasis risk of T1 colonic NETs and compare patients' long-term prognosis after LE or radical surgery (RS).

METHODS

The Surveillance Epidemiology and End Results database was used to identify patients with T1 colonic NETs (2004‒2015). Multivariable logistic regression was performed to assess factors associated with metastasis risk. Propensity score matching was used to balance the variables. Cancer-specific survival (CSS) and overall survival (OS) were calculated to estimate the prognosis of patients with T1N0M0 colonic NETs who underwent LE or RS.

RESULTS

Of the 610 patients with colonic NETs, 46 (7.54%) had metastasis at diagnosis. Tumor size (11-20 mm) (OR = 9.51; 95% confidence interval (CI): 4.32‒21.45; P < 0.001), right colon (OR = 15.79; 95% CI 7.20‒38.56; P < 0.001), submucosal infiltration (OR = 2.08; 95% CI 0.84‒5.57; P = 0.125) were independent risk factors associated with metastasis. Of the 515 patients with T1N0M0 colonic NETs, the overall long-term prognosis of LE was as good as that of RS groups (after matching, 5-year CSS: 97.9% vs. 94.6%, P = 0.450; 5-year OS: 92.7% vs. 85.6%, P = 0.009).

CONCLUSION

Tumor size (11‒20 mm) and site (right colon) are associated with metastasis in T1 colonic NETs. In the absence of metastasis, LE could be a viable option for 0‒10 mm T1 colonic NETs with well/moderate differentiation in the left colon in terms of long-term survival.

Stratification of rate of lymph node metastasis according to risk factors and oncologic outcomes in patients who underwent radical resection for rectal neuroendocrine tumors

PURPOSE

Most predictive factors for lymph node metastasis in rectal neuroendocrine tumors (NETs) have been based on local and endoscopic resection. We aimed to evaluate the risk factors for lymph node metastasis in patients who underwent radical resection for rectal NETs and stratify the risk of lymph node metastasis.

METHODS

Sixty-four patients who underwent radical resection for rectal NETs between January 2001 and January 2018 were included. We investigated the risk factors of lymph node metastasis using clinicopathologic data. We also performed a risk stratification for lymph node metastases using the number of previously known risk factors. For oncologic outcomes, the 5-year overall survival and recurrence-free survival were evaluated in both groups.

RESULTS

Among the patients who underwent radical surgery, 32 (50.0%) had lymph node metastasis and 32 (50.0%) had non-lymph node metastasis. In the multivariable analysis, only the male sex was identified as a risk factor for lymph node metastasis (odds ratio, 3.695; 95% confidence interval, 1.128-12.105; P=0.031). When there were 2 or more known risk factors, the lymph node metastasis rate was significantly higher than when there were one or no risk factors (odds ratio, 3.667; 95% confidence interval, 1.023-13.143; P=0.046). There was also no statistical difference between the 2 groups in 5-year overall survival (P=0.431) and 5-year recurrence-free survival (P=0.144).

CONCLUSION

We found that the rate of lymph node metastasis increased significantly when the number of known risk factors is 2 or more.

The Incidence of Rectal Neuroendocrine Tumors Is Increasing in Younger Adults in the US, 2001-2020

Prior non-comparative data showed increasing incidence of rectal neuroendocrine tumors (RNET) in the US. We aimed to evaluate age-specific RNET incidence rates and time-trends in demographic- and tumor-specific populations. The RNET age-adjusted incidence rates were calculated from the United States Cancer Statistics (USCS) database between 2001 and 2020. The population was stratified by age into older (≥55 years) and younger adults (<55 years), as well as by sex and race. The tumors were categorized by their stage at diagnosis into early and late. The annual percentage change (APC) and average APC (AAPC) were estimated using joinpoint regression and Monte Carlo permutation analysis. Pairwise comparison assessed for parallelism and coincidence. There were 59,846 patients diagnosed with RNET between 2001 and 2020 (50.3% women). Overall, the RNET incidence rates during this period were increasing in younger but not older adults (AAPC = 3.12 vs. -1.10; AAPC difference = 4.22, p < 0.001), with non-identical non-parallel data (p-values < 0.001). While similar results were seen in men, a greater age-specific difference was noted in women (AAPC = 3.31 vs. -1.10; AAPC difference = 4.41, p = 0.003). The difference between younger and older adults was seen in non-Hispanic White (AAPC-difference = 4.89; p < 0.001) and non-Hispanic Black (AAPC-difference = 3.33; p = 0.03) patients, and, in most years, among Hispanic and Non-Hispanic Asian/Pacific Islander patients, and it was mostly driven by early-stage tumors (AAPC-difference = 3.93; p < 0.001). The nationwide data show a significantly increasing RNET incidence in younger adults, most notably in younger women and in early-stage tumors, seen in various races. Future studies should evaluate RNET risk factors and outcomes in demographic-specific populations.

Comparison of endoscopic submucosal resection with ligation and endoscopic submucosal dissection for small rectal neuroendocrine tumors: A multicenter retrospective study

OBJECTIVES

Endoscopic submucosal resection with band ligation (ESMR-L) and endoscopic submucosal dissection (ESD) are both standard endoscopic resection methods for rectal neuroendocrine tumors (NETs) <10 mm in size. However, there is no definitive consensus on which is better. Here, we compared the efficacy of ESMR-L and ESD for small rectal NETs.

METHODS

This was a multicenter retrospective cohort study including 205 patients with rectal NETs who underwent ESMR-L or ESD. Treatment outcomes were compared by univariate analysis, multivariate analysis, and inverse probability treatment weighting (IPTW) using propensity scores. Subgroup analysis evaluated the impact of the endoscopist's experience on the technical outcome.

RESULTS

Eighty-nine patients were treated by ESMR-L and 116 by ESD. The R0 resection rate was not significantly different between the two (90% vs. 92%, p = 0.73). The procedure time of ESMR-L was significantly shorter than for ESD (17 min vs. 52 min, p < 0.01) and the hospitalization period was also significantly shorter (3 days vs. 5 days, p < 0.01). These results were confirmed by multivariate analysis and also after IPTW adjustment. The procedure time of ESD was significantly prolonged by a less-experienced endoscopist (49 min vs. 70 min, p = 0.02), but that of ESMR-L was not affected (17 min vs. 17 min, p = 0.27).

CONCLUSIONS

For small rectal NETs, both ESMR-L and ESD showed similar high complete resection rates. However, considering the shorter procedure time and shorter hospitalization period, ESMR-L is the more efficient treatment method, especially for less-experienced endoscopists.

Clinical outcomes and risk factors associated with poor prognosis after endoscopic resection of 10-20 mm rectal neuroendocrine tumors: a multicenter, retrospective study of 10-year experience

BACKGROUND

The efficacy of endoscopic resection for of 10-20 mm rectal neuroendocrine tumor (NET) remains controversial. We aimed to evaluate the clinical outcomes and risk factors associated with poor prognosis after endoscopic resection of 10-20 mm rectal NET and to determine the optimal treatment.

METHODS

Patients who underwent endoscopic resection for rectal NET in four tertiary hospitals were enrolled, and data on with the clinical outcomes and risk factors related to poor prognosis were retrospectively analyzed.

RESULTS

A total of 105 patients who underwent endoscopic submucosal resection (ESD; n = 65, 61.9%), modified endoscopic mucosal resection (mEMR; n = 31, 29.5%), and conventional EMR (cEMR; n = 9, 8.6%) were enrolled. The mean follow-up period was 41.2 ± 21.9 months. In the morphologic findings, the mean diameter was 11.6 mm (range 10-19); the shape was sessile (50.5%) and mixed type (49.5%), and surface depression was observed in 41.9% of patients. In the histologic findings, 87.6% of patients had G1 and 12.4% G2 tumor grade, and 3.8% of patients had lymphovascular invasion. The overall en bloc and histologically complete (R0) resections were 99.1% and 76.2%, respectively. cEMR was a less-frequently developed R0 resection. In the univariate and multivariate analyses for R0 resection, only surface depression was significantly associated. Regional or distant organs metastasis during follow-up developed in three patients (2.9%) and was significantly associated with female sex, redness, G2 tumor grade, and non-ESD methods.

CONCLUSION

Patients who underwent endoscopic resection of 10-20 mm rectal NET had good prognosis; therefore, endoscopic resection can be considered as the first-line treatment, particularly for 10-14 mm rectal NET. However, the risk factors, such as female sex, redness, G2 tumor grade and non-ESD methods, were associated with regional or distant metastases during follow-up. Therefore, patients with these risk factors should be carefully monitored.

Rectal neuroendocrine tumors in a colon cancer screening colonoscopy program. Sixteen-year single institution experience

OBJECTIVES

Rectal neuroendocrine tumors (rNETs) are potentially malignant lesions. In our study, we aimed to retrospectively check whether the rectal neuroendocrine tumors were found in colonoscopy examinations carried out as a part of Polish colonoscopy screening program (PCSP).

MATERIALS AND METHODS

We retrospectively analyzed the colonoscopy and histopathological database of examinations conducted as a part of PCSP in our institution in the years 2005-2021. We also checked the method by which the tumor was removed, its characteristics based on photo documentations and followed up the patients.

RESULTS

The 10568 colonoscopy examinations were performed in PCSP in the years 2005-2021. Seven patients with a mean age of 53 with rNETs (1 in every 1510 colonoscopy) were detected. The polyp mean size was 5 mm. All the lesions were well differentiated tumors. First half of the colonoscopy examinations was performed in the years 2005-2012 and in that time three rNETs were detected, four rNETs were detected in the years 2012-2021. Even despite their typical appearance the neuroendocrine origin was not suspected in majority of cases and all tumors, except one, were removed with improper method. One of the patients underwent transanal endoscopic microsurgery of the scar. All patients are disease free in median follow-up of 108 months.

CONCLUSION

Rectal NETs are detected in the screening colonoscopy program. In majority of cases, they are not suspected by endoscopists on colonoscopy, but diagnosed after removal in histopathological examinations. There is a need of education of endoscopists in recognition and methods of treatment of rNETs.

Is lymphatic invasion of microrectal neuroendocrine tumors an incidental event?: A case report

BACKGROUND

A rectal neuroendocrine tumor (rNET) is a malignant tumor originating from neuroendocrine cells. Currently, tumor size is the primary basis for assessing tumor risk.

CASE SUMMARY

This article reports the case of a 46-year-old male patient who underwent a colonoscopy that found a 3 mm rectal polypoid bulge. The pathological examination of a sample collected with biopsy forceps revealed a neuroendocrine tumor. Further endoscopic submucosal dissection rescue therapy was used. The presence of lymphatic vessels indicated that the tumor had infiltrated the negative resection margin. The lesion was located in the distal rectum near the anal canal. Therefore, to ensure the patient’s quality of life, follow-up observation was conducted after full communication with the patient. No tumor recurrence or distant metastasis has been found during the 13-mo follow-up after surgery.

CONCLUSION

Despite the presence of lymphatic invasion and extremely small diameter rNETs in our case, this phenomenon may not imply a higher risk of distant lymph node and organ metastasis.

Survival in patients with neuroendocrine tumors of the colon, rectum and small intestine

BACKGROUND

Neuroendocrine neoplasms (NENs) of the colon, rectum and small intestine (SI) are increasing in incidence and prevalence. We evaluated the 5-year overall survival (OS), and cancer-specific survival (CSS).

METHODS

The Surveillance, Epidemiology, and End Results (SEER) 18 registry from 2000 to 2017 was accessed to identify patients with colonic, rectal, and SI NENs.

RESULTS

46,665 patients were diagnosed with NENs of the colon (n = 10,518, 22.5%), rectum (18,063, 38.7%), and SI (18,084, 38.8%). By tumor site alone, patients with well-differentiated neuroendocrine tumors (NETs) of the rectum had improved 5-year OS (HR 0.72, 95% CI 0.68-0.77, p < 0.001). However, patients with rectal poorly-differentiated neuroendocrine carcinomas (NECs) who underwent oncologic resection had lower 5-year OS (35.1%) compared to colon (41.9%), and SI (72.5%).

CONCLUSIONS

Surgical resection may improve 5-year OS for NECs of the SI and colon, except in the rectum where survival was reduced. More frequent surveillance and timely initiation of systemic therapy should be considered for rectal NECs.

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.

Epidemiological, clinical and endoscopic characteristics of colorectal neuroendocrine neoplasms: a population-based study in the Netherlands

Background and study aims  Neuroendocrine neoplasms (NEN) account for a small number of colorectal neoplasms. Endoscopic detection is essential for diagnosis, treatment and follow-up. Little is known about incidence of NENs in colonoscopy populations or the relationship between clinical, endoscopic and histopathologic features. We evaluated epidemiology, endoscopic and clinical characteristics of colorectal NENs in a population-based cohort. Patients and methods  Medical records of NEN cases were cross-linked with the national pathology database from January 2001 to December 2015, in South Limburg County, the Netherlands, covering four endoscopy units. Senior pathologists reviewed and classified NENs using World Health Organization 5th edition (2019) guidelines. Results  The number of colorectal NEN diagnoses was stable over time with 0.6 NEN per 1,000 patients. A total of NENs were detected in 85 patients: 65 neuroendocrine tumors (NETs) and 20 poorly differentiated neuroendocrine carcinomas (NECs). Rectal NETs were usually small sessile/submucosal lesions with yellowish (lipoma-like) color. Colonic NETs were larger sessile/submucosal lesions with darker color compared to background. Colorectal NECs presented as large, dark-colored lesions with ulcerated/necrotizing areas. Conclusions  Our population-based data point to a stable and low incidence of 0.6 NEN per 1,000 patients in the Netherlands. Rectal NETs mainly present as small sessile yellowish lesions. Colonic NETs present as larger and darker lesions than background mucosa and NECs as darker lesions than background with ulceration/necrosis. Standardized endoscopic characterization of colorectal NENs is necessary to improve recognition of these lesions and provide a basis for evidence-based treatment and surveillance recommendations.

Recurrence after endoscopic resection of small rectal neuroendocrine tumors: a retrospective cohort study

PURPOSE

According to the European Neuroendocrine Tumor Society consensus guidelines, rectal neuroendocrine tumors (NETs) up to 10 mm in size and without poor prognostic factors could be safely removed with endoscopic resection, suggesting omitting surveillance colonoscopy after complete resection. However, the benefit of surveillance colonoscopy is still unknown. In this study, we aimed to report the outcomes after endoscopic resection of small rectal NETs using our surveillance protocol.

METHODS

This retrospective cohort study included patients who underwent endoscopic resection for rectal NETs sized up to 10 mm from January 2013 to December 2019 at our center. We excluded patients without surveillance colonoscopy and those lost to follow-up. We strictly performed surveillance colonoscopy 1 year after endoscopic resection, and every 2 to 3 years thereafter. The primary outcomes were tumor recurrence and occurrence of metachronous tumors during followup.

RESULTS

Of the 54 patients who underwent endoscopic resection for rectal NETs during the study period, 46 were enrolled in this study. The complete resection rates by endoscopic mucosal resection, precutting endoscopic mucosal resection, and endoscopic submucosal dissection were 92.3% (12 of 13), 100% (21 of 21), and 100% (12 of 12), respectively. There was no local or distant recurrence during the median follow-up of 39 months. However, we found that 8.7% (4 of 46) of patients developed metachronous NETs. All metachronous lesions were treated with precutting endoscopic mucosal resection.

CONCLUSION

Surveillance colonoscopy is reasonable after endoscopic resection of small rectal NETs for timely detection and treatment of metachronous lesions. However, larger collaborative studies are needed to influence the guidelines.

Comparison of characteristics between true rectal neuroendocrine tumors and rectal hyperplastic polyps among patients with endoscope-diagnosed rectal neuroendocrine tumors

Background

To explore the white light endoscopy and endoscopic ultrasonography (EUS) features of rectal hyperplastic polyps (rHP) misdiagnosed as rectal neuroendocrine neoplasms (rNENs). In rNENs with a diameter of 5-10 mm, the endoscopic findings are not typical and some of them are similar to rHP, so it is not uncommon to misdiagnose rNENs as rHP. However, misdiagnosis of rHP as rNENs has not been reported in the literature, which can alert clinicians to the existence of this possibility and avoid over-treatment.

Methods

We collected 245 cases of rectal submucosal tumor (SMT) diagnosed by endoscopy in our hospital from January 2015 to December 2020 and 103 patients with suspected rNENs identified through endoscopy. A retrospective analysis was conducted of the shape, color, vascular dilatation, and boundary on the surface of the lesion under white light endoscope, and the source, boundary, and echo characteristics of EUS. We also analyzed the endoscopic features of rHP misdiagnosed as rNENs. Endoscopic diagnosis and pathological diagnosis were reviewed by a senior endoscopic expert and pathologist respectively. The counting data were tested and analyzed by χ2 test and Fisher exact probability method.

Results

A total of 103 cases of rNENs were diagnosed by endoscope, among whom 75 cases were confirmed as rNENs (72.8%) and 8 cases as rHP (7.8%) by histopathology. There was no significant difference between rNENs and rHP in terms of gender, age, clinical manifestation, shape and color of lesions, dilatation of blood vessels on the surface, and location of lesions. Meanwhile, there were significant differences in whether the boundary of the lesion was clear under white light endoscopy, and the source, echo, and boundary of the lesion under EUS.

Conclusions

The morphology of some rHP is similar to rNENs under endoscopy. The boundary is clear under white light endoscopy and the source, echo, and boundary under EUS are helpful for the diagnosis of rNENs and rHP.

miR-144-3p/miR-451a promotes lymphovascular invasion through repression of PTEN/p19 in rectal neuroendocrine tumors

BACKGROUND AND AIM

Although rectal neuroendocrine tumor (NET-G1) have potential metastatic capability, even among small tumors, no predictive biomarker for invasion and metastasis has been reported. We analyzed microRNA (miRNA) expression profiles in rectal NET-G1 tissues with and without lymphovascular invasion (LVI). Moreover, we then investigated their target genes to clarify the mechanism of invasion/metastasis in NET-G1.

METHODS

miRNA array analysis was performed using seven rectal NET-G1 tissues with LVI and seven without LVI. miRNA expression was confirmed by quantitative real-time PCR. A NET cell line H727 was transfected with miRNA mimic or target gene small interfering RNA, and migration and invasion assays were performed.

RESULTS

The expression levels of miR-144-3p and miR-451a were significantly higher in NET-G1 with LVI versus without LVI, as determined by miRNA array analysis and RT-qPCR. A significant correlation was observed between miR-144-3p and miR-451a expression levels, strongly suggesting miR144/451 cluster overexpression in NET-G1 with LVI. Bioinformatic analysis of target genes revealed that miR-144-3p and miR-451a directly interact with PTEN and p19 mRNA, respectively. Immunohistochemistry revealed significantly lower expression of PTEN and p19 in NET-G1 tissues with LVI than in those without LVI. The miR-144-3p and miR-451a mimic significantly increased cell migration/invasion capability, respectively. Knockdown of PTEN and p19 induced significant augmentation of cell invasion and migration capability, respectively.

CONCLUSIONS

Our data suggest that overexpression of miR-144/miR-451 cluster promotes LVI via repression of PTEN and p19 in rectal NET-G1 cells. miR-144/451 cluster may be a novel biomarker for predicting invasion/metastasis in rectal NET-G1.

Prognostic Evaluation of Patients with Rectal Neuroendocrine Neoplasms and Hepatic Metastases: A SEER Database Analysis

Background. This study is aimed at investigating the clinical characteristics and prognosis-affecting factors of patients with rectal neuroendocrine neoplasms (r-NENs) and hepatic metastases and offering a scientific-theoretical basis for selective use of an optimized treatment method for r-NENs. Methods. This study was retrospectively evaluated based on the analysis of the data from Surveillance, Epidemiology, and End Results (SEER) database between 2010 and 2016. Results. A total of 4,723 r-NEN patients were enrolled in this study, including 168 patients with hepatic metastases (3.56%). Kaplan-Meier analysis revealed that the overall survival (OS) of patients with hepatic metastases receiving primary tumor excision was obviously greater than that of patients without receiving primary tumor excision (OS: nonsurgical patients vs. patients undergoing local resection: $P<0.0001$ and nonsurgical patients vs. patients undergoing radical resection: $P<0.0001$ ); the patients with hepatic metastases in the chemotherapy group had a significantly worse prognosis compared with those in the nonchemotherapy group (OS: $P=0.021$ ). Multivariate cox regression analysis revealed that independent affecting factors of overall and tumor-related prognoses in patients with hepatic metastases included tumor grade (G3 and G4), surgical treatment, and chemotherapy. Conclusion. Among r-NEN patients with hepatic metastases, those undergoing radical excision of lower-grade tumors and chemotherapy will have a better prognosis.

An update on the diagnosis of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) arise from neuroendocrine cells found throughout the gastrointestinal tract and islet cells of the pancreas. The incidence and prevalence of GEP-NENs have been increasing each year due to higher awareness, improved diagnostic modalities, and increased incidental detection on cross-sectional imaging and endoscopy for cancer screening and other conditions and symptoms. GEP-NENs are a heterogeneous group of tumors and have a wide range in clinical presentation, histopathologic features, and molecular biology. Clinical presentation most commonly depends on whether the GEP-NEN secretes an active hormone. The World Health Organization recently updated the classification of GEP-NENs to introduce a distinction between high-grade neuroendocrine tumors and neuroendocrine carcinomas, which can be identified using histology and molecular studies and are more aggressive with a worse prognosis compared to high-grade neuroendocrine tumors. As our understanding of the biology of GEP-NENs has grown, new and improved diagnostic modalities can be developed and optimized. Here, we discuss clinical features and updates in diagnosis, including histopathological analysis, biomarkers, molecular techniques, and radiology of GEP-NENs. We review established diagnostic tests and discuss promising novel diagnostic tests that are currently in development or require further investigation and validation prior to broad utilization in patient care.

Prognosis of rectal neuroendocrine tumors after endoscopic resection: a single-center retrospective study

BACKGROUND

The efficacy of endoscopic resection in patients with rectal neuroendocrine tumors (NETs) which are less than 20 mm in diameter remains unclear. This study aimed to investigate the efficacy and outcomes of different types of endoscopic resection in patients with NETs.

METHODS

We performed a retrospective analysis and follow-up on 98 patients who underwent endoscopic resection for rectal NETs between August 2010 and October 2019 at Guangdong Provincial People's Hospital, China. The lesions were preoperatively classified according to their endoscopic morphology and measured by endoscopic ultrasound. Patients were divided into modified endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) groups depending on the endoscopic treatment they received. The en bloc resection rate, histopathological complete resection rate, and the complication rate of the 2 groups were evaluated after the operation. The risk factors for incomplete resection were also analyzed.

RESULTS

The average diameter of the 98 NETs was 6.29±2.90 mm (range, 2-15 mm). The en bloc resection rate of the modified EMR and ESD treatment groups was 97.2% (35/36) and 100% (62/62), respectively. The histopathological complete resection rate was 86.1% (31/36) and 87.1% (54/62), respectively. No tumor recurrence or tumor-related death occurred. There were no statistically significant differences in the rate of histopathological complete resection, perforation, or delayed hemorrhage between the 2 groups (P>0.05). Multivariate analysis demonstrated that the depth of tumor invasion (P=0.007) and tumor diameter (P<0.001) were independent risk factors for histopathological complete resection.

CONCLUSIONS

Modified EMR and ESD are safe and effective endoscopic approaches for the resection of rectal NETs ≤15 mm in diameter. Endoscopic resection requires a comprehensive preoperative evaluation of risk factors including the depth of tumor invasion and tumor diameter.

Evaluation of radical surgical treatment in the management of 58 locally advanced rectal neuroendocrine neoplasms, one multicenter retrospective study

BACKGROUND

Locally advanced rectal neuroendocrine neoplasms (NENs) are rare, and the therapeutic effects of surgery in improving the prognosis have been questioned in previous reports.

MATERIALS AND METHODS

The research included 58 consecutive patients with locally advanced rectal NENs from three Chinese medical centers between 2000 and 2020. All have received radical surgical treatment. The clinicopathological and survival data were collected. Kaplan-Meier methods and a Cox proportional hazards regression model were used to evaluate the prognosis and identify independent prognostic factors.

RESULTS

All patients were followed up for a median period of 36 (2-125) months. Of the 58 patients, 13 (22.4%) had G1 neuroendocrine tumors (NETs), 15 (25.9%) had G2 NETs, 6 (10.3%) had G3 NETs, and the remaining 24 (41.4%) patients had G3 neuroendocrine carcinomas (NECs). The 1-year and 3-year disease-free survival (DFS) rates were 64.5% and 48.8%, respectively. The 1-year and 3-year overall survival (OS) rates were 90.5% and 75.4%, respectively. Univariate analysis demonstrated that tumor differentiation (p = 0.002), gross morphology (p = 0.009), T stage (p = 0.024), and extramural vascular invasion (p = 0.009) were associated with the OS. The subsequent multivariate analysis confirmed that tumor differentiation [hazard ratio (HR) = 6.002, 95% confidence interval (CI): 1.210-29.767, p = 0.028] and gross morphology (HR = 3.438, 95% CI: 1.038-11.382, p = 0.043) were independent prognostic factors affecting the clinical outcomes.

CONCLUSIONS

Rectal NENs are a heterogeneous group of diseases. The survival benefits obtained from surgery vary widely based on the tumor clinicopathological features. Patients with G3 NECs and ulcerative mass are at high risks of poor prognosis.

Comparable survival benefit of local excision versus radical resection for 10- to 20-mm rectal neuroendocrine tumors

OBJECTIVE

The optimal surgical management for 10- to 20-mm rectal neuroendocrine tumors (RNET) is still a matter of debate. This study aimed to explore the optimal surgical approach for 10- to 20-mm RNET by comparing the outcomes between local excision and radical resection.

METHOD

We extracted clinicopathological information of 10- to 20-mm RNET from the Surveillance, Epidemiology, and End Results (SEER) database. The 1:2 propensity score matching (PSM) method was used to balance the imbalanced baseline covariates (P < 0.05) between the local excision group and radical resection group. A Cox proportional hazards model was used to identify the risk factors associated with cancer-specific survival (CSS) and overall survival (OS).

RESULT

A total of 531 RNET patients 10-20 mm in size were included. Patients receiving radical resection had larger tumor sizes (P < 0.001), higher T stages (P < 0.001), higher N stages (P < 0.001), higher M stages (P = 0.002) and higher grades (P = 0.041). For 10-20 mm RNET patients, radical resection had no survival benefit compared with local excision (CSS: HR = 2.048, 95% CI 0.553-7.576, P = 0.283; OS: HR = 1.090, 95% CI 0.535-2.219, P = 0.813). After 1:2 PSM, there was no significant difference between local excision and radical resection. Radical resection still had no survival benefit over local excision (CSS: HR = 0.449, 95% CI 0.050-4.022, P = 0.474; OS: HR = 1.408, 95% CI 0.488-4.061, P = 0.527). In a multivariate analysis of CSS, age >60 years old (P = 0.005), tumour size 14-20 mm (P = 0.011) and M1 stage (P < 0.001) were identified as independent prognostic factors for worse CSS. In multivariate analysis of OS, age>60 years (P＜0.001), male sex (P = 0.007), black race (P = 0.016), and T2/T3/T4 stage (P = 0.007) were significantly associated with worse OS. N stage was not an independent predictive factor for CSS and OS.

CONCLUSION

This study revealed that for 10- to 20-mm RNET patients, there was no survival benefit for radical resection compared with local excision, which suggested that local excision may be an adequate treatment for these patients.

Localized Well-Differentiated Rectal Neuroendocrine Tumors - Where Are We in 2021?

Neuroendocrine tumors (NETs) are slow-growing malignancies with distinct biologic and clinical characteristics. Most rectal-NETs are localized and well-differentiated, usually carrying an excellent prognosis. In this review, we aim at describing the epidemiology, clinical characteristics and therapeutic approaches for well-differentiated rectal NETs.

Quality of pathology reporting and adherence to guidelines in rectal neuroendocrine neoplasms: a Belgian national study

The incidence of neuroendocrine neoplasms (NEN) in the rectum is rising since the introduction of colonoscopy screening programs. Guidelines, such as the European NeuroEndocrine Tumor Society (ENETS) algorithm, are mainly based on expert opinion. The goal of this nationwide study is to gain a better insight into the evolution in pathology reporting and adherence to the ENETS guidelines in Belgium. In Belgium, all NENs have to be reported to the Belgian Cancer Registry. We thoroughly reviewed all available pathology reports, coded as rectal NEN between 2004 and 2015, and reclassified according to World Health Organisation (WHO) classification 2019. To evaluate the adherence to the ENETS guidelines, population-based cancer registry data were linked with the medical procedures of the Belgian Health Insurance database. A total of 670 rectal NEN were retained and 16% of the cases needed reclassification. Annual incidence between 2004 and 2015 tripled from 0,20 to 0,61 per 100.000 inhabitants. Reporting of Ki67 proliferation index ameliorated most, while reporting of tumor size, lymphovascular and perineural invasion remained disappointing. Endoscopic ultrasound was performed in only 36.6% of the cases, while the mostly recommended mode of treatment (endoscopic/surgical/no resection) was followed in the majority of the cases. Incidence of rectal NEN in Belgium increased throughout the years and quality of pathology reporting improved especially after the WHO classification update in 2010. The growing awareness and knowledge among clinicians and pathologists in the community counters the need for centralization.

Endoscopic submucosal dissection versus endoscopic mucosal resection for rectal carcinoid tumor. A meta-analysis and meta-regression with single-arm analysis

OBJECTIVE

As there has been so far no consensus on the best endoscopic resection technique, a meta-analysis was conducted to compare the efficacy and safety of endoscopic submucosal dissection (ESD) and endoscopic mucosal resection (EMR) for treating rectal carcinoid tumors.

METHODS

MEDLINE and EMBASE databases were searched for articles on the treatment of rectal carcinoid tumors using ESD vs EMR published up to October 2020 for outcomes including en bloc and complete resection, margin involvement, procedure time, requirement for additional surgery, bleeding, perforation and recurrence. Risk ratio and weighted mean differences were used for a DerSimonian and Laird random effects pairwise meta-analysis. Single-arm meta-analyses of proportions and random effects meta-regression analysis were also conducted.

RESULTS

Twenty-two studies involving 1360 rectal carcinoid tumors were included, in which 655 and 705 rectal carcinoid tumors were resected with ESD and EMR, respectively. The resection efficacy of ESD was comparable to that of EMR for tumors <10 mm. However, there were a significantly higher complete resection rate, and lower rates of vertical margin involvement and requirement for additional surgery using ESD than using EMR for tumors ≤20 mm. ESD had a longer procedure time and an increased likelihood of bleeding than EMR.

CONCLUSIONS

ESD is more effective in providing a curative treatment for rectal carcinoid tumors ≤20 mm in size as ESD can achieve a higher complete resection rate with lower vertical margin involvement than EMR. While they are suitable for treating rectal carcinoid tumors <10 mm as both techniques provide similar efficacy.

Recurrence and Survival of Neuroendocrine Neoplasms of the Rectum: Single-Center Experience

BACKGROUND

In 2010, the World Health Organization proposed that rectal neuroendocrine neoplasms (NENs) be considered malignant. We hypothesized that patients with small, low-grade, locally excised tumors have a low risk of recurrence and death.

METHODS

Retrospective review of institutional database 2006-2017 including consecutive adults with newly diagnosed rectum NENs. Outcome measures included risk of recurrence and 5-year overall survival.

RESULTS

A total of 122 patients were diagnosed with rectal NENs. Most patients were asymptomatic and diagnosed during screening colonoscopy (80, 66.1%), had small tumors (median 0.6 cm, IQR 0.5-1) with intact muscularis propria on EUS (62/65, 95.4%), and were low grade (2017 WHO grades 1-2, n = 116, 95.1%). Lymph node and distant metastasis were found in 4 (3.3%) and 4 (3.3%) of patients, respectively. Patients were treated with local excision in 93.4% of cases with polypectomy (52, 42.6%), endoscopic mucosal resection (48, 39.3%), and transanal excision (14, 11.5%). Three patients (2.5%) required abdominoperineal resection or low anterior resection, and five patients (4.1%) received adjuvant chemotherapy. Of 87 patients surveilled, 4 (4.6%) recurred at a median time of 1 year (IQR 0.6-8). Death from neuroendocrine neoplasms occurred in 5 (4.1%) patients, all with lymph node (1/4) or metastatic disease (4/5) on presentation. Median time to death from NEN was 0.8 years (0.7-2.4). Overall 5-year survival for patients with localized disease was 98.2% (95% CI 93-99.5, Fig. 1).

CONCLUSION

Patients with small, low grade rectal NENs treated with local excision have excellent oncologic outcomes.

The incidence, treatment and survival of patients with rare types of rectal malignancies in the Netherlands: A population-based study between 1989 and 2018

AIM

To describe the incidence, treatment and survival of patients with rare types of rectal malignancies in the Netherlands.

METHODS

Data of patients with rectal malignancies diagnosed in the Netherlands between 1989 and 2018 were retrieved from the Netherlands Cancer Registry and grouped according to the RARECARE cancer list. Age-standardised incidence rates were calculated using the European Standard Rate. The Joinpoint Regression Program was used for analysing trends and joinpoints and for the estimation of annual percentage changes (APCs). Patient characteristics, treatment details and relative survival (RS) were reported for different histological types of rectal malignancies and compared between different time periods. RS was assessed using Kaplan-Meier analysis and log-rank test.

RESULTS

A total of 88,299 cases of rectal malignancies were included of which 2125 (2.5%) were categorised as rare histological subtypes. The incidence of rectal neuro-endocrine tumours (NET) (APC: 6.2%, 95% confidence interval [CI]: 5.4%; 7.1%), rectal sarcoma (APC: 5.8%, 95% CI: 2.9%; 8.7%) and rectal adenocarcinoma (APC 1.0%, 95% CI: 0.26%; 1.8%) increased. Prognosis was best in patients with rectal NET (5-year RS: 72.4%, 95% CI: 70.1%; 74.7%) and worst in patients with rectal melanoma (5-year RS: 8.9%, 95% CI: 5.1%; 15.7%). RS has improved in patients with rectal adenocarcinoma, rectal sarcoma and rectal lymphoma in 2008-2018 (p-values p < 0.001, p = 0.023 and p = 0.029).

CONCLUSION

Significant increases in incidence were observed for different types of rectal malignancies. Differences in incidence, treatment and survival found in this study could be useful to make clinicians aware of specific diseases.

Endoscopic and surgical treatment of T1N0M0 colorectal neuroendocrine tumors: a population-based comparative study

BACKGROUND

With the rapid advances in endoscopic technology, endoscopic therapy (ET) is increasingly applied to the treatment of small (≤ 20 mm) colorectal neuroendocrine tumors (NETs). However, long-term data comparing ET and surgery for management of T1N0M0 colorectal NETs are lacking. The purpose of this work was to compare overall survival (OS) and cancer-specific survival (CSS) of such patients with ET or surgery.

METHODS

Patients with T1N0M0 colorectal NETs were identified within the Surveillance Epidemiology and End Results (SEER) database (2004-2016). Demographics, tumor characteristics, therapeutic methods, and survival were compared. Propensity score matching (PSM) was used 1:3 and among this cohort, Cox proportional hazards regression models were performed to evaluate correlation between treatment and outcomes.

RESULTS

Of 4487 patients with T1N0M0 colorectal NETs, 1125 were identified in the matched cohort, among whom 819 (72.8%) underwent ET and 306 (27.2%) underwent surgery. There was no difference in the 5-year and 10-year OS and CSS rates between the 2 treatment modalities. Likewise, analyses stratified by tumor size and site showed that patients did not benefit more from surgery compared with ET. Moreover, multivariate analyses found no significant differences in OS [Hazard Ratio (HR) = 0.857, 95% Confidence Interval (CI): 0.513-1.431, P = 0.555] and CSS (HR = 0.925, 95% CI: 0.282-3.040, P = 0.898) between the 2 groups. Similar results were observed when comparisons were limited to patients with different tumor size and site.

CONCLUSIONS

In this population-based study, patients with lesions < 10 mm treated endoscopically had comparable long-term survival compared with those treated surgically, which demonstrates ET as an alternative to surgery in T1N0M0 colorectal NETs of < 10 mm. Further high-quality prospective studies are warranted to comprehensively evaluate the role of ET in patients with tumors 10 to 20 mm.

Size Criteria Is Not Sufficient in Selecting Patients for Local Excision Versus Radical Excision for Rectal Neuroendocrine Tumors >2 cm: A National Cancer Database Analysis

BACKGROUND

Patients with rectal neuroendocrine tumors >2 cm often undergo radical surgery, despite limited data supporting this practice. Five- and 10-year survival rates for these patients have been reported previously as 74.8% and 58.6%.

OBJECTIVE

Overall survival was compared between local excision and radical surgery and pN0 and pN1 within the radical surgery subgroup for rectal neuroendocrine tumors >2 cm. Factors independently associated with survival were identified.

DESIGN

A retrospective, nationwide, multivariate regression analysis was performed.

SETTINGS

Data are from the National Cancer Database (2004-2013).

PATIENTS

Patients with rectal neuroendocrine tumors >2 cm, excluding stages T4 and M1, were included.

MAIN OUTCOME MEASURES

Outcome measures were overall survival and independent risk factors for overall survival based on multivariate regression analysis.

RESULTS

Each group had 178 patients. After local excision, 5- and 10-year overall survival rates were 88% and 72% vs 51% and 42% after radical surgery (p < 0.001). A multivariate Cox proportional hazards model showed similar survival (p = 0.96). Tumor factors independently associated with survival were nodal metastasis (HR = 2.01 (95% CI, 1.01-3.97)), poorly differentiated tumors (HR = 4.82 (95% CI, 1.65-14.01)), and undifferentiated tumors (HR = 9.91 (95% CI, 2.77-35.49)). After radical surgery, patients with and without nodal metastasis had 5-year survival rates of 44% vs 59% (unadjusted p = 0.09; adjusted p = 0.11), with insufficient 10-year survival data.

LIMITATIONS

The study is a retrospective analysis and includes only Commission on Cancer-accredited hospitals. Long-term follow-up was limited. Lymphovascular invasion was missing for a majority of patients analyzed.

CONCLUSIONS

Local excision for select patients with rectal neuroendocrine tumors >2 cm is a viable alternative to radical surgery. Nodal status and tumor grade independently predict survival and should be factored into surgical intervention selection. In higher-risk patients selected for radical surgery, survival was similar between the pN0 and pN1 groups, possibly indicating a benefit of radical surgery for these patients. See Video Abstract at http://links.lww.com/DCR/B455.

EL CRITERIO DE TAMAO NO ES SUFICIENTE PARA SELECCIONAR PACIENTES PARA LA ESCISIN LOCAL VERSUS ESCISIN RADICAL PARA TUMORES NEUROENDOCRINOS RECTALES CM ANLISIS DE UNA BASE DE DATOS NACIONAL DE CANCER

ANTECEDENTES:Los pacientes con tumores neuroendocrinos rectales >2 cm a menudo se someten a cirugía radical, a pesar de los datos limitados que respaldan esta práctica. La supervivencia a cinco y diez años para estos pacientes se había informado anteriormente como 74,8% y 58,6%, respectivamente.OBJETIVO:Se comparó la supervivencia global entre escisión local y cirugía radical, y pN0 y pN1 dentro del subgrupo de cirugía radical para tumores neuroendocrinos rectales >2 cm. Se identificaron factores asociados de forma independiente con la supervivencia.DISEÑO:Se realizó un análisis retrospectivo de regresión multivariante a nivel nacional.AJUSTE:Los datos provienen de la Base de Datos Nacional sobre el cáncer (2004-2013).PACIENTES:Pacientes con tumores neuroendocrinos rectales > 2 cm, excluyendo los estadios T4 y M1.PRINCIPALES MEDIDAS DE RESULTADO:Las medidas de resultado fueron la supervivencia general y los factores de riesgo independientes para la supervivencia general según el análisis de regresión multivariante.RESULTADOS:Cada grupo tuvo 178 pacientes. Después de la escisión local, la supervivencia global a cinco y diez años fue del 88% y 72% frente al 51% y el 42% después de la cirugía radical (p <0,001). Un modelo multivariado de riesgos proporcionales de Cox mostró una supervivencia similar (p = 0,96). Los factores tumorales asociados de forma independiente con la supervivencia fueron metástasis ganglionares (HR = 2,01; IC, 1,01-3,97), tumores pobremente diferenciados (HR = 4,82, IC, 1,65-14,01) y tumores indiferenciados (HR = 9,91, IC, 2,77-35,49). Después de la cirugía radical, los pacientes con y sin metástasis ganglionar tuvieron una supervivencia a cinco años del 44% frente al 59%, respectivamente (p no ajustado = 0,09; p ajustado = 0,11), con datos insuficientes de supervivencia a diez años.LIMITACIONES:El estudio es un análisis retrospectivo e incluye solo hospitales acreditados por la Comisión de Cáncer. El seguimiento a largo plazo fue limitado. La mayoría de los pacientes analizados no tenían invasión linfovascular.CONCLUSIONES:La escisión local para pacientes seleccionados con tumores neuroendocrinos rectales >2 cm es una alternativa viable a la cirugía radical. El estado ganglionar y el grado del tumor predicen de forma independiente la supervivencia y deben tenerse en cuenta en la selección de la intervención quirúrgica. En los pacientes de mayor riesgo seleccionados para cirugía radical, la supervivencia fue similar entre los grupos pN0 vs. pN1, lo que posiblemente indica un beneficio de la cirugía radical para estos pacientes. Consulte Video Resumen en http://links.lww.com/DCR/B455.

Recurrence pattern and surveillance strategy for rectal neuroendocrine tumors after endoscopic resection

BACKGROUND AND AIM

Endoscopic resection is highly effective treatment option for rectal neuroendocrine tumors (NETs) as they usually present as small localized tumors. However, there are no well-established surveillance strategies following endoscopic resection. We established our own protocol for the surveillance of rectal NETs after endoscopic resection since 2013. This study aimed to assess the outcome and to optimize the surveillance strategies after endoscopic resection.

METHODS

We retrospectively analyzed the data of patients with endoscopically treated rectal NETs between January 2013 and April 2018 at Samsung Medical Center. We analyzed 337 patients with a median follow-up duration of 35.0 months (min-max: 12.0-88.3).

RESULTS

A total of 329 (97.6%) patients had tumors ≤ 1 cm in size, and eight (2.4%) patients had tumors > 1 cm in diameter. Synchronous rectal NETs were diagnosed in nine (2.7%) patients. Thirteen (3.9%) patients were identified as having positive resection margins. Regardless of the salvage treatment, none of these patients developed recurrence. Metachronous rectal NETs were diagnosed in nine (2.7%) patients. Metachronous lesions were associated with the number of synchronous lesions at initial diagnosis (P < 0.001, hazard ratio = 1.75, 95% confidence interval = 1.38-2.23). Extracolonic metastasis was not detected in this study.

CONCLUSION

Although initial screening for detecting metastatic lesions using computed tomography is recommended, repeated imaging for detecting extracolonic recurrence was not necessary for small non-metastatic rectal NETs. However, regular endoscopic follow-up seems reasonable, especially in case of synchronous rectal NETs, for detecting metachronous rectal NETs.

Endoscopically removed rectal NETs: a nationwide cohort study

PURPOSE

Rectal neuroendocrine tumours (NETs) often present as an incidental finding during colonoscopy. Complete endoscopic resection of low-grade NETs up to 10 mm is considered safe. Whether this is also safe for NETs up to 20 mm is unclear. We performed a nationwide study to determine the risk of lymph node and distant metastases in endoscopically removed NETs.

METHODS

All endoscopically removed rectal NETs between 1990 and 2010 were identified using the national pathology database (PALGA). Each NET was stratified according to size, grade and resection margin. Follow-up was until February 2016.

RESULTS

Between 1990 and 2010, a total of 310 NETs smaller than 20 mm were endoscopically removed. Mean size of NETs was 7.4 mm (SD 3.5). In 49% of NETs (n = 153), no grade (G) could be assessed from the pathology report, 1% was G2 (n = 3), and the remaining NETs were G1. Median follow up was 11.6 years (range 4.9-26.0). During follow-up, 30 patients underwent surgical resection. Lymph node or distant metastasis was seen in 3 patients (1%) which all had a grade 2 NET. Mean time from endoscopic resection to diagnosis of metastases was 6.1 years (95% CI 2.9-9.2).

CONCLUSION

No lymph node or distant metastases were seen in endoscopically removed G1 NETs up to 20 mm during the long follow-up of this nationwide study. This adds evidence to the ENET guideline that endoscopic resection of G1 NETs up to 20 mm appears to be safe.

Indications for lateral lymph node dissection in patients with rectal neuroendocrine tumors: A case report and review of the literature

The optimal surgical indications for small rectal neuroendocrine tumors (NETs) are controversial. Generally, treatment guidelines for rectal NETs >2 cm or with potential lymph node (LN) metastasis recommend formal oncologic low anterior resection (LAR) with total mesorectal excision (TME). However, rectal NETs have the potential to metastasize to the lateral lymph nodes (LLNs). To the best of our knowledge, there are no detailed reports in English on LLN metastasis from rectal NETs. A 47-year-old man diagnosed with a rectal NET underwent endoscopic submucosal dissection (ESD). The pathological diagnosis was NET G1. The tumor was 10 mm in diameter, and the tumor depth reached the submucosal layer. A period of 3 years after ESD, the patient was diagnosed with LN metastasis in the mesorectum and LLN metastasis on the left side from the NET. Robotic TME and bilateral LN dissection were performed. The pathological findings indicated that two of the 18 LNs in the mesorectum were metastatic, and all the LLNs on the left side were negative. In contrast, 1 of the 6 LLNs on the right side was metastatic. Early-stage rectal NETs can metastasize to the LLNs, and it is very difficult to detect LLN metastasis based on size alone. TME alone may be insufficient to treat rectal NETs, and additional LLN dissection may be an important treatment strategy. However, it is increasingly difficult to determine the surgical indications for optimally timed LLN dissection.

Prediction of the World Health Organization Grade of rectal neuroendocrine tumors based on CT histogram analysis

OBJECTIVES

To investigate the diagnostic value of contrast-enhanced computed tomography (CECT) histogram analysis in predicting the World Health Organization (WHO) grade of rectal neuroendocrine tumors (R-NETs).

MATERIALS AND METHODS

A total of 61 (35 G1, 12 G2, 10 G3, and 4 NECs) patients who underwent preoperative CECT and treated with surgery to be confirmed as R-NETs were included in this study from January 2014 to May 2019. We depicted ROIs and measured the CECT texture parameters (mean, median, 10th, 25th, 75th, 90th percentiles, skewness, kurtosis, and entropy) from arterial phase (AP) and venous phase (VP) images by two radiologists. We calculated intraclass correlation coefficient (ICC) and compared the histogram parameters between low-grade (G1) and higher grade (HG) (G2/G3/NECs) by applying appropriate statistical method. We obtained the optimal parameters to identify G1 from HG using receiver operating characteristic (ROC) curves.

RESULTS

The capability of AP and VP histogram parameters for differentiating G1 from HG was similar in several histogram parameters (mean, median, 10th, 25th, 75th, and 90th percentiles) (all p < 0.001). Skewness, kurtosis, and entropy on AP images showed no significant differences between G1 and HG (p = 0.853, 0.512, 0.557, respectively). Entropy on VP images was significantly different (p = 0.017) between G1 and HG, however, skewness and kurtosis showed no significant differences (p = 0.654, 0.172, respectively). ROC analysis showed a good predictive performance between G1 and HG, and the 75th (AP) generated the highest area under the curve (AUC = 0.871), followed by the 25th (AP), mean (VP), and median (VP) (AUC = 0.864). Combined the size of tumor and the 75th (AP) generated the highest AUC.

CONCLUSIONS

CECT histogram parameters, including arterial and venous phases, can be used as excellent indicators for predicting G1 and HG of rectal neuroendocrine tumors, and the size of the tumor is also an important independent predictor.

Factors associated with worse outcomes for colorectal neuroendocrine tumors in radical versus local resections

Background

Colorectal neuroendocrine tumors (NETs) are the most common NETs of the gastrointestinal tract. Due to the rarity, colorectal NETs are understudied and are not clearly understood. Our study sought to identify the factors associated with worse outcomes for colorectal NETs following resection.

Methods

We identified patients diagnosed with colorectal NETs [2004-2014] who underwent resection from the National Cancer Data Base. Non-NETs were excluded. Overall survival (OS) was evaluated using the Kaplan Meier method. Cox proportional hazards and logistic regression models were used to assess factors associated with radical versus local resection, OS and LOS.

Results

A total of 7,967 colon and 11,929 rectal NETs were analyzed. The majority of colon (93.4%) and rectal (89.1%) NETs underwent radical and local resection respectively. The 5-year OS was 69% and 92% for colon and rectal NETs respectively. Older age (OR 1.45, CI 1.37-1.53) and clinical stage 4 (OR 9.91, CI 4.56-21.52) were associated with higher odds for colonic radical resection. Lowest median income quartile (OR 1.41, CI 1.21-1.64) and African Americans (OR 1.26, CI 1.07-1.49) experienced higher mortality for colon and rectal NETs respectively.

Conclusions

Racial minority and low-income patients experience worse outcomes for colorectal NETs following resection.

Highly proliferative anal neuroendocrine carcinoma: molecular and clinical features of a rare, recurrent case in complete remission

BACKGROUND

Poorly differentiated anal neuroendocrine carcinomas (ANECs) are rare lesions with poor prognosis, and the molecular etiology is only partially understood.

CASE PRESENTATION

At our institution, we have treated and followed a patient with such a rare ANEC. He had primarily surgery followed by three rounds of repeated surgery for loco-regional recurrences. He also received three different combinations of chemotherapy and external beam radiation. At last follow-up 13 years since the primary diagnosis, the patient had been in complete remission for nine years. The patient's medical files were re-examined, including laboratory, radiology and clinical examinations. Histopathology was re-assessed, and expanded immunohistochemistry was performed from tissue specimens from the four surgical procedures. In addition, the molecular genetic status was evaluated through next-generation sequencing. The initial tumor was consistent with a 59 mm small cell neuroendocrine cancer with a Ki-67 index of 80%. Regional lymph node metastases were evident, and immunohistochemistry supported a neuroendocrine origin. A PCR screening detected human papilloma virus type 45 DNA (high-risk subtype), and focused next-generation sequencing found a missense mutation in the Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) gene. In tissues representing subsequent recurrences, the Chromogranin A expression was lost, and the Ki-67 index increased to 90%.

CONCLUSIONS

For the first time, we report the detection of HPV45 in a case of ANEC. To our belief, PIK3CA mutations have also not been previously demonstrated in this tumor entity. In highly malignant ANECs, cure can in rare cases be achieved. Although speculative, expression of HPV45 and/or the PIK3CA mutation may have contributed to the favorable outcome.

Metachronous liver metastases after long-term follow-up of endoscopic resection for rectal neuroendocrine neoplasms: a report of three cases

Background

Rectal neuroendocrine neoplasms (NENs) are rare, but their incidence has increased in recent years. The metastasis rate is low in cases of a tumor diameter < 1 cm or depth of invasion lower than the submucosa; therefore, the European Neuroendocrine Tumor Society (ENETS) and the North American Neuroendocrine Tumor Society (NANETS) consensus guidelines recommend endoscopic resection. Since little has been reported on the long-term prognosis of endoscopic resection for rectal NEN, consensus is lacking regarding the follow-up period after endoscopic resection.

Case presentation

Here, we report three cases of metachronous liver metastasis after long-term follow-up of endoscopic mucosal resection (EMR) for rectal NEN. The pathological findings indicated a depth lower than the submucosa and complete radical resection in all cases and lymphovascular invasion in only one case. All three cases showed metachronous multiple liver metastases after 9–13 years of follow-up for EMR, despite achieving complete resection and without muscular invasion.

Conclusions

Metachronous liver metastases may occur after long interval following endoscopic resection; thus, long-term follow-up is necessary after endoscopic resection for rectal NEN.

Synchronous NET and colorectal cancer development: a case report

Background

The incidence of synchronous gastrointestinal neuroendocrine tumors (GI-NETs) and colorectal cancer is very low.

Case presentation

We present a 72-year-old man diagnosed with a rectal neuroendocrine tumor (NET) with multiple organ metastases and simultaneous sigmoid colon cancer. Although the NET was his prognostic factor, he underwent a laparoscopic sigmoidectomy at first because it was expected that the colon cancer would cause obstruction or bleeding during NET treatment. Subsequently, he started taking everolimus.

Conclusions

We should consider surgical resection of the synchronous cancer before systemic therapy for a GI-NET regardless of the difference in prognosis between synchronous tumors, if the cancer may impair the continuation of systemic therapy.

Rectal NETs and rectosigmoid junction NETs may need to be treated differently

Neuroendocrine tumors (NETs) are heterogeneous, and the incidence of NETs is rapidly increasing. We observed different survival in patients with rectal NETs and rectosigmoid junction NETs, which are treated similarly. We included patients with rectal and rectosigmoid junction NETs from the SEER database. The 5‐year survival was set as the end‐point. 6675 patients with rectal NETs and 329 patients with rectosigmoid junction NETs, were eligible for the analysis. Initially, the survival analyses suggested that the 5‐year survival significantly differed between the patients with rectal and rectosigmoid junction NETs (HR = 0.82, 95% CI 0.70‐0.95; P = .01). Tumor differentiation, an invasion deeper than T2, and lymph node and distant metastases were still important risk factors affecting survival for both location. While, the males showed better survival (HR = 0.69, 95% CI 0.55‐0.88; P < .01) and primary tumor surgery had no benefits (P = .56) for patients with rectosigmoid junction NETs. The factors that predict regional lymph node metastases varied by location. In rectal NETs, invasion deeper than T1 and a tumor larger than 1 cm could significantly increase the risk of regional lymph node metastases (all OR > 5, P < .01). In rectosigmoid junction NETs, the risk of regional lymph node metastases was considered significantly higher with invasion deeper than T1 (all OR > 5, P < .01) and a tumor larger than 2 cm (OR = 31.32, 95% CI 2.53‐387.57; P < .01). We advocate a clear and consistent definition of the rectosigmoid junction for future studies, and more studies are needed to determine the reason underlying differences between rectum and rectosigmoid junction.

The ENETS TNM staging and grading system accurately predict prognosis in patients with rectal NENs

BACKGROUND

Factors associated with rectal NENs prognosis are poorly investigated.

AIM

To evaluate the prognostic role of the ENETs staging and grading systems in rectal NENs.

METHODS

Tertiary referral, multicenter, retrospective study. Factors associated with OS and PFS were investigated by Cox-regression analysis, with best size cut-offs calculated by ROC analysis.

RESULTS

Of 100 patients (mean age 55, 45% male, mean size 16.2 mm) 62, 5, 10 and 23 were TNM stage 1 to 4, and 63, 15 and 22 were G1, G2 and G3. Primary treatment was endoscopic snare resection in 62%, endoscopic mucosal resection/endoscopic submucosal dissection in 10%, surgery in 20% and medical treatment in 8%. The best size cut-offs to predict OS and PFS were 10 and 12 mm. During a mean follow-up of 40.7 months 12% died and 26% progressed. The 5-year OS and PFS were 79.5% and 65.2%. Stage IV and G3 were associated with worse OS (HR 8.16; p = 0.002; HR 15.57; p = 0.0004) and PFS (HR 14.26 p < 0.0001; HR 6.42; p = 0.0007).

CONCLUSION

Both staging and grading accurately predict rectal NENs prognosis. Size alone has limited accuracy as 26% of patients with stage IV and 16% with G3 have a primary tumour≤10 mm.

Clinicopathological characteristics and frequency of multiple rectal neuroendocrine tumors: a single-center retrospective study

BACKGROUND

Rectal multiple neuroendocrine tumors (M-NETs) are rare, with only few epidemiologic reports on the topic. Therefore, their clinicopathological features are not completely known, and the appropriate treatment strategy has not been established.

PURPOSE

This study aimed to compare the clinicopathological malignant potential (lymphatic or venous invasion-positive and lymph node metastasis rates) of M-NETs with that of solitary NETs (S-NETs).

METHODS

We retrospectively investigated 369 patients with NETs of the rectum. Patients who underwent colonoscopy at the Cancer Institute Hospital between January 1979 and 2016 and diagnosed with S-NETs were included, and S-NETs were found in 348 patients. Patients with M-NETs were classified into two groups as follows: patients with < 8 tumors (several (S) group, n = 21) and those with ≥ 8 tumors (numerous (N) group, n = 3).

RESULTS

The overall frequency of M-NETs was 5.7% and that of the N group was 0.8%. The mean tumor diameter in the N group was 6.0 mm (range, 4-8 mm). The lymphatic invasion rates of the S-NETs, and S and N groups of the M-NETs were 8.9%, 5.6%, and 66.7%, respectively. Moreover, the lymph node metastasis rates were 9.2%, 11.1%, and 33.3, respectively.

CONCLUSIONS

While M-NETs in the S and N groups had different characteristics, they were rarer in the N group. The N group may have higher rates of lymphatic invasion and lymph node metastasis regardless of tumor size.

Lymphovascular invasion as a prognostic value in small rectal neuroendocrine tumor treated by local excision: A systematic review and meta-analysis

Because rectal neuroendocrine tumors (NETs) are usually small-sized despite of malignant potential, endoscopic resection techniques are recommended. It is unclear whether the lymphovascular invasion (LVI) in the endoscopic resected specimens of small rectal NETs should be indicated for completion surgery. We performed a systematic review and meta-analysis for the incidence of LVI in small rectal NETs (≤20 mm) treated by endoscopic resection and its prognostic impacts. We searched the relevant literature published before January 2019. A total of 21 publications including 1816 patients were enrolled. Overall prevalence of LVI in small rectal NETs was 21.8%. Immunohistochemical method significantly increased the detection rate of LVI up to 35.8% compared than H&E staining only (13.2%). Tumor size more than 5 mm was a risk factor for LVI in small rectal NET, whereas tumor grade did not influence the risk. The LVI in the endoscopic resected specimens was a risk factor for subsequent lymph node metastasis. Separately analyzed in detail, the vascular invasion had a stronger impact on lymph node metastasis than the lymphatic invasion. The prognosis of endoscopically treated rectal NET with LVI was excellent with only 0.3% of recurrence rate during the 5-year follow-up period. LVI is highly prevalent and a risk factor for lymph node metastasis in the small rectal NETs. Endoscopically treated small rectal NETs had excellent short-term prognoses despite of LVI. Immediate completion radical surgery is not absolutely necessary for the LVI-positive small rectal NETs. However, long-term follow-up is recommended for any delayed recurrence.