A Randomized Phase III Trial of Complete Mesocolic Excision Compared with Conventional Surgery for Right Colon Cancer: Interim Analysis of a Nationwide Multicenter Study of the Italian Society of Surgical Oncology Colorectal Cancer Network (CoME-in trial).

BACKGROUND: Although complete mesocolic excision (CME) is supposed to be associated with a higher lymph node (LN) yield, decreased local recurrence, and survival improvement, its implementation currently is debated because the evidence level of these data is rather low and still not supported by randomized controlled trials. METHOD: This is a multicenter, randomized, superiority trial (NCT04871399). The 3-year disease-free survival (DFS) was the primary end point of the study. The secondary end points were safety (duration of operation, perioperative complications, hospital length of stay), oncologic outcomes (number of LNs retrieved, 3- and 5-year overall survival, 5-year DFS), and surgery quality (specimen length, area and integrity rate of mesentery, length of ileocolic and middle-colic vessels). The trial design required the LN yield to be higher in the CME group at interim analysis. RESULTS: Interim data analysis is presented in this report. The study enrolled 258 patients in nine referral centers. The number of LNs retrieved was significantly higher after CME (25 vs. 20; p = 0.012). No differences were observed with respect to intra- or post-operative complications, postoperative mortality, or duration of surgery. The hospital stay was even shorter after CME (p = 0.039). Quality of surgery indicators were higher in the CME arm of the study. Survival data still were not available. CONCLUSIONS: Interim data show that CME for right colon cancer in referral centers is safe and feasible and does not increase perioperative complications. The study documented with evidence that quality of surgery and LN yield are higher after CME, and this is essential for continuation of patient recruitment and implementation of an optimal comparison. Trial registration The trial was registered at ClinicalTrials.gov with the code NCT04871399 and with the acronym CoME-In trial.

Complete mesocolic excision for right colon cancer: Is D3 lymphadenectomy necessary?

AIM: Although complete mesocolic excision (CME) for colon cancer is oncologically sound, to date, there has been no consensus on the extent of lymphadenectomy in radical right colectomy. This study essentially compared the perioperative and survival outcomes of CME with two templates of lymphadenectomy for right colon cancer. METHOD: This was a propensity matched, retrospective analysis of a single centre, prospectively maintained database of all patients undergoing elective right colectomy for nonmetastatic, biopsy-proven adenocarcinoma from November 2013 to October 2018. CME + D3 was adopted selectively, documented prospectively, and compared with patients undergoing CME + central vascular ligation (CVL). The only technical difference between the groups was the excision of the surgical trunk of Gillot in the CME + D3 group. Postoperative, long-term outcomes and patterns of recurrence were compared between the groups. RESULTS: Of the 244 eligible patients, 88 (36.1%) and 156 (63.9%) underwent CME + D3 and CME + CVL, respectively. Matched groups (72 [CME + D3] vs. 108 [CME + CVL]) showed no difference in histology, tumour grade, postoperative complications, mortality, and hospital stay. CME + D3 was preferentially performed laparoscopically (35.2% vs. 9%), was associated with lower blood loss (215 mL vs. 297 mL, p = 0.001), higher nodal yield (31 vs. 25 nodes, p = 0.003) and a higher incidence of chyle leak (4 vs. 0, p = 0.013). At a median follow-up of more than 57 months, there was no significant difference in local recurrence, disease-free or overall survival. CONCLUSION: In this retrospective study, lymphadenectomy along the superior mesenteric vein, as a component of CME for right colon cancer, offered a higher nodal yield with no improvement in oncological outcome. Dissection of the SMV, over and above a D2 dissection, could therefore be restricted to specialized colorectal units until further studies establish the incremental oncological benefit of this extended lymphadenectomy or define a patient group in whom it is beneficial.

Colon cancer: feeling the imbalance?

While neoadjuvant chemotherapy has become the standard of care for rectal cancers in most centres, there is much interest in neoadjuvant chemotherapy in colon cancer after the recent publication of the FOxTROT trial. The management of colon cancers seems to be heading down the same path as rectal cancer, where the radicality of surgery is replaced by chemotherapy intensification. The role of demanding procedures such as complete mesocolic excision with central venous ligation in this new paradigm of upfront chemotherapy remains uncertain and uninvestigated.

Laparoscopic right hemicolectomy: a SICE (Società Italiana di Chirurgia Endoscopica e Nuove tecnologie) network prospective study on the approach to right colon lymphadenectomy in Italy: is there a standard?-CoDIG 2 (ColonDx Italian Group).

BACKGROUND: Colon cancer is a disease with a worldwide spread. Surgery is the best option for the treatment of advanced colon cancer, but some aspects are still debated, such as the extent of lymphadenectomy. In Japanese guidelines, the gold standard was D3 dissection to remove the central lymph nodes (203, 213, and 223), but in 2009, Hoenberger et al. introduced the concept of complete mesocolic excision, in which surgical dissection follows the embryological planes to remove the mesentery entirely to prevent leakage of cancer cells and collect more lymph nodes. Our study describes how lymphadenectomy is currently performed in major Italian centers with an unclear indication on the type of lymphadenectomy that should be performed during right hemicolectomy (RH). METHODS: CoDIG 2 is an observational multicenter national study that involves 76 Italian general surgery wards highly specialized in colorectal surgery. Each center was asked not to modify their usual surgical and clinical practices. The aim of the study was to assess the preference of Italian surgeons on the type of lymphadenectomy to perform during RH and the rise of any new trends or modifications in habits compared to the findings of the CoDIG 1 study conducted 4 years ago. RESULTS: A total of 788 patients were enrolled. The most commonly used surgical technique was laparoscopic (82.1%) with intracorporeal (73.4%), side-to-side (98.7%), or isoperistaltic (96.0%) anastomosis. The lymph nodes at the origin of the vessels were harvested in an inferior number of cases (203, 213, and 223: 42.4%, 31.1%, and 20.3%, respectively). A comparison between CoDIG 1 and CoDIG 2 showed a stable trend in surgical techniques and complications, with an increase in the robotic approach (7.7% vs. 12.3%). CONCLUSIONS: This analysis shows how lymphadenectomy is performed in Italy to achieve oncological outcomes in RH, although the technique to achieve a higher lymph node count has not yet been standardized. Trial registration (ClinicalTrials.gov) ID: NCT05943951.

Learning curve and safety of the implementation of laparoscopic complete mesocolic excision with intracorporeal anastomosis for right-sided colon cancer: results from a propensity score-matched study.

BACKGROUND: Retrospective studies and randomized controlled trials support the safety of laparoscopic complete mesocolic excision (CME) for the treatment of right-sided colon cancer (RSCC). Few studies, however, examine the learning curve of this operation and its impact on safety during an implementation period. We aim to evaluate the learning curve and safety of the implementation of laparoscopic CME with intracorporeal anastomosis for RSCC. METHODS: Consecutive patients undergoing a laparoscopic right colectomy with intracorporeal anastomosis for RSCC between January 2016 and June 2023 were included. Clinical, perioperative, and histopathological variables were collected. Correlation and cumulative sum (CUSUM) analyses between the operating time and case number were performed. Breakpoints of the learning curve were estimated using the broken-line model. CME and conventional laparoscopic right colectomy outcomes were compared after propensity score matching (PSM). RESULTS: Two hundred and ninety patients underwent laparoscopic right colectomy during study period. One hundred and eight met inclusion criteria. After PSM, 56 non-CME and 28 CME patients were compared. CME group had a non-statistically significant tendency to a longer operating time (201 versus 195 min; p = 0.657) and a shorter hospital stay (3 versus 4 days; p = 0.279). No significant differences were found in total complication rates or their profile. Correlation analysis identified a significant trend toward operating time reduction with increasing case numbers (Pearson correlation coefficient = - 0.624; p = 0.001). According to the CUSUM analysis, an institutional learning curve was deemed completed after 13 cases and the broken-line model identified three phases: learning (1-6 cases), consolidation (7-13 cases), and mastery (after 13 cases). CONCLUSION: The learning curve of laparoscopic CME for RSCC can be achieved after 13 cases in centers with experience in advanced laparoscopic surgery and surgeons with familiarity with this technique. Its implementation within this setting seems to be as safe as performing a conventional right colectomy.

Radiological characteristics and diagnostic clues for persistent descending mesocolon in patients with rectal cancer.

PURPOSE: Persistent descending mesocolon (PDM) increases the difficulty and colonic ischemia in the surgery of colorectal cancer, but the preoperative diagnostic criteria have not yet been clearly demonstrated. This study explored the MR imaging features and diagnostic criteria of PDM to improve the preoperative diagnostic rate. METHODS: The clinical data of 54 patients with PDM and 270 patients without PDM who underwent rectal surgery at the Department of Colorectal Surgery, Fujian Medical University Union Hospital, from March 2018 to December 2022 were analyzed, retrospectively. The radiological parameters of PDM from MRI were analyzed. RESULTS: On MRI T2WI axial image, the left edge of the abdominal aorta was defined as the reference line. The shortest vertical distance between the right edge of the descending colon and this line (dN) and the maximum transverse diameter of the peritoneal cavity (dA) at the same level and the maximum vertical distance between the right edge of the descending colon and this line (dW) were measured. There were significant statistical differences in dN, dW, dN/dW, and dN/dA between the PDM group and the non-PDM group. dN, dN/dW, and dN/dA have high diagnostic performance for the PDM. dN < 4.16 cm, dN/dW < 0.52, and dN/dA < 0.15 can all be used as clues to diagnose PDM. CONCLUSIONS: We propose a feasible set of diagnostic criteria for PDM based on abdominal MRI, which can quickly and accurately diagnose PDM, and provide some reference for preoperative planning and surgical decision-making.

Developing a phantom for simulating robotic-assisted complete mesocolic excision using 3D printing and medical imaging.

BACKGROUND: Robotic-assisted complete mesocolic excision is an advanced procedure mainly because of the great variability in anatomy. Phantoms can be used for simulation-based training and assessment of competency when learning new surgical procedures. However, no phantoms for robotic complete mesocolic excision have previously been described. This study aimed to develop an anatomically true-to-life phantom, which can be used for training with a robotic system situated in the clinical setting and can be used for the assessment of surgical competency. METHODS: Established pathology and surgical assessment tools for complete mesocolic excision and specimens were used for the phantom development. Each assessment item was translated into an engineering development task and evaluated for relevance. Anatomical realism was obtained by extracting relevant organs from preoperative patient scans and 3D printing casting moulds for each organ. Each element of the phantom was evaluated by two experienced complete mesocolic excision surgeons without influencing each other's answers and their feedback was used in an iterative process of prototype development and testing. RESULTS: It was possible to integrate 35 out of 48 procedure-specific items from the surgical assessment tool and all elements from the pathological evaluation tool. By adding fluorophores to the mesocolic tissue, we developed an easy way to assess the integrity of the mesocolon using ultraviolet light. The phantom was built using silicone, is easy to store, and can be used in robotic systems designated for patient procedures as it does not contain animal-derived parts. CONCLUSIONS: The newly developed phantom could be used for training and competency assessment for robotic-assisted complete mesocolic excision surgery in a simulated setting.

Modified Rosi-Cahill technique after left extended colectomy for splenic flexure advanced tumors.

Advanced splenic flexure tumors are uncommon and have a higher risk of relapse. To ensure that the resection includes the entire area of lymphatic drainage with a complete mesocolic excision (CME), a left extended colectomy is needed. In peritoneal carcinomatosis, there is often extensive involvement of the sigma and splenic flexure of the colon. In many instances, total colectomies are chosen for these patients, even when a significant portion of the colon could be preserved. The potential impact on quality of life after splenic flexure colon resection is discussed, as well as the importance of anatomical knowledge and expertise in performing this type of surgery. Overall, this work presents a modified technique that aims to improve the outcomes and quality of life for patients with splenic flexure colon cancer. Creating a tension-free anastomosis after extended left-sided colorectal resection is challenging. There is a negative impact on quality of life when an ileorectal anastomosis is created. The colorectal anastomosis performed after modified Rosi-Cahill or Deloyers' technique allows reduced small bowel bacterial overgrowth, achieves better water and sodium absorption, and altogether permits improved stool consistency. There are potential advantages of the Rosi-Cahill technique over other popular options such as Deloyers' procedure as there is no torsion of the ileocolic vessels and no mesenteric windows. A video was recorded showing a potential pitfall during Deloyers' technique resulting in the creation of a mesenteric window. The proper rotation of the colon during the modified Rosi-Cahill procedure was also filmed. Overall, this work presents a modified technique for reconstruction after left extended colectomy that aims to improve the outcomes and quality of life for patients with splenic flexure colon cancer.

Laparoscopic D3 right hemicolectomy with intracorporeal anastomosis.

Complete mesocolic excision (CME) with D3 lymphadenectomy for colon cancer has been shown to improve overall as well as disease-free survival compared to conventional right hemicolectomy. Performing a laparoscopic CME/D3 right hemicolectomy with intracorporeal anastomosis (ICA) can be technically demanding even for experienced operators. Here, we present a systematic, standardized approach to the surgery.

Proposal for standardization of laparoscopic D3 lymphadenectomy for right colon cancer.

BACKGROUND: This study presents a laparoscopic surgical protocol for right hemicolectomy and D3 lymphadenectomy (R-D3L) in right colon cancer and reports the oncological outcomes based on a prospective series. METHODS: The study comprises two phases. In the first phase, a dynamic demonstration of the R-D3L surgical protocol is provided through textual explanation, illustrations, and edited surgical videos. The protocol emphasizes technical steps such as dissection of the embryological plane of the right mesocolon, high tie of ileocolic vessels, surgical trunk of Gillot dissection, and high tie of superior right colic vein (SRCV). In the second phase, a prospective observational study was conducted involving patients undergoing R-D3L surgery with this protocol between July 2015 and July 2021. Demographic, perioperative, and postoperative variables are analyzed, along with anatomopathological variables and oncological outcomes. RESULTS: A total of 33 patients were analyzed. Median operative time was 202 min. Perioperative bleeding occurred in 6%. Postoperative complications were mild (Clavien-Dindo III in 2%). Postoperative ileus was observed in 15%. No anastomotic dehiscence was reported. The median postoperative stay was 7 days. The median number of resected lymph nodes was 26, with 27% having positive nodes and 70% were classified as stage T3 or T4. After a median follow-up of 45 months, local recurrence, distant recurrence, and carcinomatosis rates were 0%. Mortality rate from other causes was 9%. CONCLUSION: The surgical protocol shown in the present study could help in the implementation of this technique in those units that consider it appropriate.

Conventional surgery in colon cancer with comparison to complete mesocolic excision and central vascular ligation: initial experience in a tertiary centre.

INTRODUCTION: The complete mesocolic excision (CME) and central vascular ligation (CVL) is an advanced surgical technique used to treat colon cancer. It combines the removal of the affected portion of the colon and surrounding lymph nodes with an improved method of controlling the vascular supply to the tumour. MATERIALS AND METHODS: A retrospective study of patients with colon cancer underwent right hemicolectomy (either CME and CVL or conventional method) were operated by colorectal surgeons in a tertiary centre in Kuala Lumpur from 2018 to 2020. We review the data to compare the oncological, pathological and surgical outcomes of both techniques. Categorical variables were presented as frequencies and percentages. Continuous variables were compared using an independent t-test or Mann-Whitney Rank U test. The chi-square test was used to determine the association between categorical variables and mortality. Statistical analysis was conducted with IBM SPSS Statistics 25.0, and statistical significance was set at p<0.05. RESULTS: A total of 30 patients (CME and CVL=15 or conventional colectomies=15) were included in this study with mean age of 65 years. There was no statistical difference between the mean age of the two groups (p=0.355). Most of the patients were Malays (46.7%) followed by Chinese (43.3 %) and Indians (10.0%). The mean (SD) = 19 (9) number of lymph nodes harvested is more in CME and CVL groups which however is not statistically significant compared to the mean (SD) = 16 (9), number of lymph nodes in conventional colectomies. The duration of surgery is longer in CME and CVL groups (214 minutes) compared to conventional colectomies (188 minutes) but with no significant statistical difference. Most of the perioperative complications were similar in both groups with no significant statistical differences. CONCLUSION: CME and CVL are not inferior to conventional surgery in colon surgery in a tertiary centre. It should be considered since the advantages such as lymph node yield and median recurrence free survival are better with similar perioperative morbidity.

Discordance in Total Mesorectal Excision Specimen Grading in a Prospective Phase 2 Multicenter Rectal Cancer Trial: Are We Overestimating the Quality of Our Resections?

OBJECTIVES: To report the results of a rigorous quality control (QC) process in the grading of total mesorectal excision (TME) specimens during a multicenter prospective phase 2 trial of transanal TME. BACKGROUND: Grading of TME specimens is based on the macroscopic assessment of the mesorectum and standardized through synoptic pathology reporting. TME grade is a strong predictor of outcomes with incomplete (IC) TME associated with increased rates of local recurrence relative to complete or near complete (NC) TME. Although TME grade serves as an endpoint in most rectal cancer trials, in protocols incorporating centralized review of TME specimens for quality assurance, discordance in grading and the management thereof has not been previously described. METHODS: A phase 2 prospective transanal TME trial was conducted from 2017 to 2022 across 11 North American centers with TME quality as the primary study endpoint. QC measures included (1) training of site pathologists in TME protocols, (2) blinded grading of de-identified TME specimen photographs by central pathologists, and (3) reconciliation of major discordance before trial reporting. Cohen Kappa statistic was used to assess agreement in grading. RESULTS: Overall agreement in grading of 100 TME specimens between site and central reviewer was rated as fair, (κ = 0.35; 95% CI: 0.10-0.61; P < 0.0001). Concordance was noted in 54%, with minor and major discordance in 32% and 14% of cases, respectively. Upon reconciliation, 13/14 (93%) major discordances were resolved. Pre versus postreconciliation rates of complete or NC and IC TME are 77%/16% and 7% versus 69%/21% and 10%. Reconciliation resulted in a major upgrade (IC-NC; N = 1) or major downgrade (NC/C-IC, N = 4) in 5 cases overall (5%). CONCLUSIONS: A 14% rate of major discordance was observed in TME grading between the site and central reviewers. The resolution resulted in a major change in final TME grade in 5% of cases, which suggests that reported rates or TME completeness are likely overestimated in trials. QC through a central review of TME photographs and reconciliation of major discordances is strongly recommended.

Involvement of transverse mesocolon is associated with development of colonic fistula in patients with acute necrotizing pancreatitis.

BACKGROUND: Involvement of transverse mesocolon (TM) during acute necrotizing pancreatitis(ANP) indicates that inflammation has spread from retroperitoneal space to peritoneum. Nevertheless, the impact of TM involvement, as confirmed by contrast-enhanced computed tomography (CECT), on local complications and clinical outcomes was poorly investigated. PURPOSE: This study aimed to explore the association between CECT-diagnosed TM involvement and the development of colonic fistula in a cohort of ANP patients. METHODS: This is a single-center, retrospective cohort study involving ANP patients admitted from January 2020 to December 2020. TM involvement was diagnosed by two experienced radiologists. The study subjects were enrolled consecutively and divided into two groups: TM involvement and non-TM involvement. The primary outcome was colonic fistula during the index admission. Clinical outcomes were compared between the two groups, and the association between the TM involvement and the development of colonic fistula was assessed using multivariable analysis to adjust for baseline unbalances. RESULTS: A total of 180 patients with ANP were enrolled, and 86 (47.8%) patients had TM involvement. The incidence of the colonic fistula is significantly higher in patients with TM involvement (16.3% vs. 5.3%;p = 0.017). Moreover, the length of hospital stay was 24(13,68) days in patients with TM involvement and 15(7,31) days in those not (p = 0.001). Analysis of multivariable logistic regression revealed that TM involvement is an independent risk factor for the development of colonic fistula (odds ratio: 10.253, 95% CI: 2.206-47.650, p = 0.003). CONCLUSION: TM involvement in ANP patients is associated with development of colonic fistula in ANP patients.

Efficacy and safety of robotic complete mesocolic excision: a systematic review.

BACKGROUND: Complete mesocolic excision (CME) consists of the complete removal of tumor-bearing soft tissues enveloped by the mesocolic fascia and radical lymphadenectomy at the origin of feeding vessels. We conducted a systematic review, evaluating the efficacy of the robotic CME (RCME) in patients with right-sided colon cancer and presenting the data in comparison to those concerning the open RC (right colectomy) with CME. METHODS: One independent researcher searched the MEDLINE-PubMed database for published and unpublished material. RESULTS: Eighty-three articles were found to refer to CME, 17 of which met the selection criteria following the PRISMA guidelines. All researchers presented short-term outcomes and agreed on the oncologic safety of CME. Different surgical approaches were proposed; however, no significant differences were noticed regarding the peri-operative outcomes. CONCLUSION: Although long-term outcomes are needed to establish it as a standard of care in right-sided colon cancer, RCME is a procedure that gains more and more grounds due to its oncologic safety. The standard medial-to-lateral approach seems to have similar results to other approaches.

Validation of the German classification system for quality assessment of right-sided colon cancer specimens.

AIM: The German classification system of the completeness of mesocolic excision aims to assess the quality of right-sided colonic cancer surgery by review of photographs. We aimed to validate the reliability of the classification in a clinical context. METHOD: The study was based on a cohort of patients undergoing resection for right-sided colon cancer in two university hospitals served by the same group of pathologists. Prospectively collected photographs of the specimens were assessed twice by six colorectal surgeons to determine the intra-rater and inter-rater accuracy of the German classification and a modification assessing extended right-sided resections. RESULTS: Specimens from 613 resections for right-sided colon cancer were reviewed. Twenty-one specimens were found to be non-assessable, leaving 436 right hemicolectomies, 139 extended right hemicolectomies and 17 right-sided subtotal colectomies. Intra-rater reliability was 0.57-0.74 and weighted kappa coefficients 0.58-0.74, without differences between subgroups. The percentage of agreement between all six participants was 20.3% for all specimens, 21.1% for right hemicolectomy specimens and 18.1% for extended hemicolectomy and right-sided subtotal colectomy specimens. For the right hemicolectomy specimens, the model-based kappa coefficient for agreement was 0.27 (95% CI 0.24-0.30) and for association 0.45 (95% CI 0.41-0.49). CONCLUSION: The German classification of right hemicolectomy specimens showed low intra-rater reliability and inter-rater agreement and association. The use of this classification for scientific purposes appeared not to be reliable.

The retrocolic fascial system revisited for right hemicolectomy with complete mesocolic excision based on anatomical terminology: do we need the eponyms Toldt, Gerota, Fredet and Treitz?

AIM: Right hemicolectomy with complete mesocolic excision (CME) requires the removal of an intact mesocolic envelope. The study aimed to determine, on the basis of macroscopic and microscopic anatomical studies, the optimal surgical dissection planes for CME to preserve fascial integrity. Unequivocal anatomical nomenclature was applied to describe the retrocolic fascial system and compared to frequently used eponyms (Toldt, Gerota, Fredet, Treitz). METHOD: Stepwise macroscopic dissections, cross-section studies and histological analysis were performed on body donors to identify the components of the retrocolic fascial system. Based on these anatomical findings, the optimal surgical dissection planes for CME were validated in laparoscopic training courses on body donors and in robot-assisted surgical procedures in patients. RESULTS: The mesocolic tissue and lymphovascular pedicles were enveloped by the ventral and dorsal mesocolic leaf (mesocolic fascia). The mesocolic fascia was attached to the parietal peritoneal fascia ('fascia of Toldt') along the parieto-mesocolic interface, and further cranially to the pre-duodenopancreatic fascia along the mesocolic-duodenopancreatic interface ('space of Fredet'). Dorsally, the parietal peritoneal fascia was separated from the anterior renal fascia ('fascia of Gerota') by the parieto-renal interface. Dissection along this interface in front of the anterior renal fascia followed by incision of the parietal peritoneal fascia at the duodenal border and opening the mesocolic-duodenopancreatic interface yielded the best macroscopic appearance of specimens and was considered optimal for CME. CONCLUSION: The retrocolic fascial system as well as the surgical dissection planes for CME can be described by clearly defined anatomical terms rather than potentially confusing eponyms.

Association between plane of mesocolic dissection and recurrence after complete mesocolic excision for right-sided colon cancer: a cohort study.

AIM: Dissection in the mesocolic plane is considered by some medical professionals to be crucial in complete mesocolic excision. We aimed to assess whether intramesocolic plane dissection is associated with a risk of recurrence after complete mesocolic excision for right-sided colon cancer. METHOD: This is a single-centre study based on prospectively registered data on patients undergoing resection for Union for International Cancer Control Stage I-III right-sided colon adenocarcinoma during the period 2010-2017. Patients were stratified in an intramesocolic plane group or a mesocolic plane group based on a prospective assessment of fresh specimens by a pathologist. Primary outcome was the 4.2 year risk of recurrence after inverse probability treatment weighting and competing risk analyses. RESULTS: Of 383 patients, 4 (1%) were excluded as the specimen was assessed as muscularis propria plane, 347 (91.6%) specimens were deemed as mesocolic and 32 (8.4%) as intramesocolic. The 4.2 year cumulative incidence of recurrence after inverse probability treatment weighting was 9.1% (95% CI 6.0%-12.1%) in the mesocolic group compared with 14.0% (3.6%-24.5%) in the intramesocolic group with an absolute risk difference in favour of mesocolic plane dissection of 4.9% (-5.7 to 15.6, p = 0.37). No difference was observed in the risk of local recurrence, death before recurrence or overall survival after 4.2 years between the two groups. CONCLUSION: Mesocolic plane dissection can be achieved in more than 90% of patients. The classification seems to be a guide for good surgical practice and not to be used for research purposes.

Technical assessment in minimally invasive complete mesocolic excision: Is the complete mesocolic excision competency assessment tool valid and reliable?

AIM: The complete mesocolic excision competency assessment tool (CMECAT) is a novel tool designed to assess technical skills in minimally invasive complete mesocolic excision (CME) surgery. The aim of this study was to assess construct validity and reliability of CMECAT in a clinical context. METHOD: Colorectal surgeons were asked to submit video recorded laparoscopic CME resections for independent assessment of their technical abilities. The videos were grouped by surgeons' training level, and four established CME experts were recruited as CMECAT assessors. Extended reliability analysis (G-theory) was applied to describe assessor agreement. RESULTS: A total of 19 videos and 72 assessments were included in the analysis. Overall, technical skills assessed by CMECAT improved with increased training level: the experts scored significantly better than the untrained surgeons (3.3 vs. 2.5 points; p < 0.01). On right-sided resections, significantly higher scores were reported with increased training level for all categories and sections, while for left-sided resections, the variance across groups was smaller and significantly higher scores were only reported for oncological safety describing items. Overall, assessor agreement was high (G-coefficient: 0.81). CONCLUSION: This study confirms that CMECAT can be applied to video recorded CME cases for technical skill assessment. Further, it can reliably assess technical performance in right sided CME surgery, where construct validity has now been established. More videos are required to evaluate its validity on left colonic CME. In the future, we hope CMECAT can improve feedback during CME training, serve as a tool in certification processes and contribute to distinguishing CME from conventional surgery in future research.

The mesocolic apical fragment in complete mesocolic excision colectomies: Should it be analysed separately? A proof-of-concept study.

AIM: The aim of this work is to describe a protocol and assess the feasibility of harvesting and analysing the mesocolic apical fragment (MAF) for the presence of central lymph node (LN) metastasis and extra lymphatic free tumour cells in a random subgroup extracted from a cohort of complete mesocolic excision colectomies with central vascular ligation. METHOD: Forty-seven patients diagnosed with colorectal cancer were included. A 2/2 cm pyramid of tissue was cut around the central tie and sent for pathological examination. The MAF was sectioned into 16 slices. High-definition images were taken from the slices which were merged into a panoramic three-dimensional image of the MAF. The distribution of LNs in the MAF was quantified. Immunohistochemistry staining for cytokeratin 14 was used to identify isolated tumour cells and micrometastases in the extranodal tissue. RESULTS: No tumoural cells migrating through the apical zone, outside of the LNs, were identified. Margins of resection, mesocolic tissue and LNs were all negative in the subgroup of ultrastaged MAFs. The number of examined central LNs varied between 0 and 24, with positive MAF LNs being identified only in pN2 stages. The rate of positive apical LNs in our cohort was 4.2% (n = 2). CONCLUSIONS: The MAF can be easily extracted from standard specimens, allowing for accurate analysis of lymphatic and extra-nodal tumour cells on the central resection margins, in central LNs and in the apical mesocolic tissue. Future research on larger cohorts is required to establish if analysing the MAF has an impact on patient staging, prognosis and management.

Inferior versus medial approach in laparoscopic colectomy with complete mesocolic excision and D3 lymphadenectomy for right-sided colon cancer: A propensity-score-matched analysis.

AIM: In laparoscopic colectomy with complete mesocolic excision and D3 lymphadenectomy for right-sided colon cancer, either an inferior approach (IA) or a medial approach (MA) is selected in our institution based on the surgeon's preference. The present study compared the treatment outcomes between IA and MA. METHOD: This retrospective, single-centre study using propensity score matching analysed the short- and long-term outcomes of laparoscopic surgery in patients with right-sided colon cancer from 2010 to 2019 at Cancer Institute Hospital. RESULTS: After patient selection, 1011 patients remained for the analysis, of which 67% underwent IA surgery and 33% underwent MA surgery. After propensity score matching (1:1), 325 patients in each group were analysed. Regarding the short-term outcomes, there were no significant differences in the operation time, rate of conversion to open surgery or postoperative complication rate (Clavien-Dindo Grade ≥ III) between the two groups, although the intra-operative median blood loss was significantly less in the IA group than in the MA group (IA, 13 ml vs. MA, 20 ml, P < 0.0001). Regarding the long-term outcomes, the relapse-free survival, liver-relapse-free survival, cancer-specific survival and overall survival were all similar between groups. CONCLUSION: Both the IA and MA in laparoscopic colectomy with complete mesocolic excision and D3 lymphadenectomy for right-sided colon cancer are safe and feasible approaches; the IA may have an advantage over the MA in terms of reduced intra-operative blood loss. Based on their similar oncological outcomes, either the IA or MA can be selected, based on one's preference.