Endoscopic Resection Of Colorectal Polyps Research Articles

Cold Snare Polypectomy With or Without Submucosal Injection for Endoscopic Resection of Colorectal Polyps: A Meta-Analysis of Randomized Controlled Trials.

The impact of submucosal injection during cold snare polypectomy (CSP) remains uncertain. We conducted an evidence-based comparison of conventional CSP (C-CSP) and CSP with submucosal injection (SI-CSP) for colorectal polyp resection. PubMed, Embase, and the Cochrane Library databases were searched for randomized controlled trials (RCTs) comparing C-CSP with SI-CSP. Major outcomes included the rates of complete resection, en bloc resection, polyp retrieval, and adverse events, as well as the duration of polypectomy. Data were analyzed by using a random-effects model. A total of seven RCTs were included. Complete resection rates for all polyps (RR 0.98; 95% CI 0.93-1.03), polyps ≤ 10mm (RR 0.99; 95% CI 0.96-1.02) and polyps > 10mm (RR 0.92; 95% CI 0.69-1.12) were not substantially different between C-CSP and SI-CSP groups. En bloc resection rate (RR 0.93; 95% CI 0.79-1.09) and polyp retrieval rate (RR 1.00; 95% CI 0.99-1.01) were also not significantly different between the two groups. The SI-CSP group required a prolonged polypectomy time than the C-CSP group (SMD - 0.89; 95% CI -1.29 to -0.49). Adverse events were rare in both groups. SI-CSP is not an optimal substitute for CSP in the resection of colorectal polyps, particularly diminutive and small polyps.

S1267 Rate of Colorectal Cancer Detection Using Piecemeal Endoscopic Resection of Colorectal Polyps - A Systematic Review and Meta-analysis

S1267 Rate of Colorectal Cancer Detection Using Piecemeal Endoscopic Resection of Colorectal Polyps - A Systematic Review and Meta-analysis

Effectiveness of prophylactic clipping in preventing postpolypectomy bleeding in aspirin users: a propensity-score analysis

Antithrombotic use is a significant risk factor of postpolypectomy bleeding (PPB). Evidence of prophylactic clipping is only available for proximal and large colonic lesions in the general population. Dedicated studies to examine the benefit of prophylactic clipping in patients on aspirin remain scarce. A propensity score-weighted retrospective cohort study was performed in a tertiary referral center from January 2018 to September 2021. Patients who received aspirin and underwent colonoscopic polypectomy, EMR, or endoscopic submucosal dissection were included. Data on baseline demographics, medications, and endoscopic factors (polyp number, size, location, and morphology; resection method; and prophylactic clipping) were captured. Propensity score-weighted models were developed between prophylactic clipping and no clipping groups. The primary outcome was delayed PPB within 30 days, with a composite endpoint consisting of repeated colonoscopy for hemostasis, requirement of blood transfusion, or hemoglobin drop >2 g/dL. A total of 1373 patients with 3952 polyps were included. Baseline characteristics were balanced between the 2 groups. In the multivariate analysis, the largest polyp size was a significant risk factor for PPB (odds ratio, 1.07; 95% confidence interval, 1.02-1.11; P= .002). Prophylactic clipping was not associated with a reduced risk of PPB (odds ratio, 1.34; 95% confidence interval, .83-2.18; P= .240) and did not show any risk reduction in subgroups with different polyp sizes and locations and endoscopic resection techniques. Prophylactic clipping was not associated with a lower risk of PPB in aspirin users after endoscopic resection of colorectal polyps. Aspirin use should not be regarded as the only factor for the routine use of prophylactic clips.

Endoscopic management of familial adenomatous polyposis targeting colorectal lesions greater than 5mm in size: a single-center retrospective study.

Preserving the colon while preventing colorectal cancer is challenging in patients with familial adenomatous polyposis. Although prophylactic colectomy is the current standard of care, some patients with familial adenomatous polyposis may wish to postpone colectomy as long as polyposis can be managed by endoscopic resection. This study examined our endoscopic management and prognostic results for patients with familial adenomatous polyposis who refused to undergo colectomy. We retrospectively analyzed the data of 12 patients with familial adenomatous polyposis treated at our hospital between January 1995 and December 2020. All patients opted to postpone prophylactic colectomy although they had significant polyp burdens and underwent endoscopic management, in which colorectal polyps sized > 5mm were thoroughly resected during baseline colonoscopies and subsequently, newly arising colorectal polyps sized > 5mm were periodically resected during surveillance colonoscopies. Patients (median age, 33years) were followed up for a median of 5.2years. The median number of colonoscopies and resected lesions per patient was 2 and 14 at baseline as well as, 9 and 32 during surveillance, respectively. The interval between colonoscopies was 1.0 and 7.0months for baseline and surveillance, respectively. The colons of all 12 patients were preserved, and no invasive colorectal cancer developed. In 10 patients, 35 cases of high-grade dysplasia were observed and managed by endoscopic resection. Repeated endoscopic resection of colorectal polyps sized > 5mm with appropriate surveillance may be an alternative form of endoscopic management for patients with familial adenomatous polyposis wishing to postpone colectomy.

Improvement Effect of Bifidobacterium animalis subsp. lactis MH-02 in Patients Receiving Resection of Colorectal Polyps: A Randomized, Double-Blind, Placebo-Controlled Trial.

BackgroundPostoperative symptoms, bowel dysfunction and recurrence are common problems after resection of colorectal polyps. We aimed to evaluate the efficacy of Bifidobacterium in the postoperative patients.MethodsIn this single-center, randomized, double-blind, placebo-controlled trial, adults (≥ 18 years) undergoing endoscopic resection of colorectal polyps were treated with probiotics (Bifidobacterium animalis subsp. lactis MH-02, 2 × 109 colony-forming units per packet) or placebo once daily for 7 days. The primary clinical endpoint was a reduction in the mean total postoperative symptoms score within 7 days postoperatively. Secondary clinical endpoints were the single symptom scores, time to recovery of bowel function, and changes in the intestinal microbiota. This study is registered with the number ChiCTR2100046687.ResultsA total of 100 individuals were included (48 in probiotic group and 52 in placebo group). No difference was seen in the mean scores between the two groups (0.29 vs. 0.43, P = 0.246). Colorectal polyps size (P = 0.008) and preoperative symptoms (P = 0.032) were influential factors for the primary endpoint. Besides, MH-02 alleviated difficult defecation (P = 0.045), and reduced the time to recovery of bowel function (P = 0.032). High-throughput analysis showed that MH-02 can help restore the diversity of intestinal microbiota, and increased the relative abundance of Bifidobacterium, Roseburia, Gemmiger, Blautia and Ruminococcus, while reduced the relative abundance of Clostridium at genus level (P < 0.05).ConclusionIn this prospective trial, MH-02 showed efficacy in patients with resection of colorectal polyps, particularly in the recovery of bowel function, and the changes in the intestinal microbiota may provide evidence for further exploration of the therapeutic mechanisms.

Safety of Cold Snare Polypectomy for Small Colorectal Polyps in Patients Receiving Antithrombotic Therapy

Background and AimsRecent guidelines do not specify the bleeding risk of cold polypectomy. We investigated delayed postpolypectomy bleeding (DPPB) after cold snare polypectomy (CSP) for colorectal polyps in patients receiving antithrombotic (AT) therapy. MethodsA total of 4770 patients who underwent endoscopic resection of colorectal polyps between April 2017 and December 2019 were included. Of them, we analyzed 3600 patients and 10,152 polyps with a size of < 10 mm, including 640 patients who took AT drugs. The patients were subdivided into 3 groups according to AT drug use: 1) continued use, 2) withdrawal, and 3) no use. We compared DPPB rates between hot snare polypectomy (HSP) and CSP in each group. ResultsThe DPPB rates in the CSP group were approximately one-tenth lower than those in the HSP group (per-patient analysis: 0 (0/2598) vs 0.9% (9/1002), per-polyp analysis: 0.04 (3/7928) vs 0.58% (13/2224)). The DPPB rates of HSP were significantly different among the continued use, withdrawal, and no use groups (per-polyp analysis: 2.08 (6/289), 0 (0/159), and 0.40% (7/1771), P = 0.0015). However, the DPPB rates of CSP did not differ among groups (per-polyp analysis: 0 (0/983), 0.17 (1/591), and 0.03% (2/6348), P = 0.2087). No DPPB was observed after CSP in patients with continued use of thienopyridine, aspirin, cilostazol, direct oral anticoagulants, or warfarin; except for 1 patient with direct oral anticoagulant withdrawal. ConclusionThe DPPB of CSP in patients taking an AT drug was low and similar to that in patients not taking drugs. CSP could be a safe procedure for colorectal polyps, even with continued use of AT drugs.

Delayed Bleeding After Endoscopic Resection of Colorectal Polyps: Identifying High-Risk Patients.

Delayed post-polypectomy bleeding (DPPB) is a potentially severe complication of therapeutic colonoscopy which can result in hospital readmission and re-intervention. Over the last decade, rates of DPPB reported in the literature have fallen from over 2% to 0.3–1.2%, largely due to improvements in resection technique, a shift towards cold snare polypectomy, better training, adherence to guidelines on periprocedural antithrombotic management, and the use of antithrombotics with more favourable bleeding profiles. However, as the complexity of polypectomy undertaken worldwide increases, so does the importance of identifying patients at increased risk of DPPB. Risk factors can be categorised according to patient, polyp and personnel related factors, and their integration together to provide an individualised risk score is an evolving field. Strategies to reduce DPPB include safe practices relevant to all patients undergoing colonoscopy, as well as specific considerations for patients identified to be high risk. This narrative review sets out an evidence-based summary of factors that contribute to the risk of DPPB before discussing pragmatic interventions to mitigate their risk and improve patient safety.

ID: 3527109 ENDOSCOPIC MANAGEMENT OF COLORECTAL POLYPS IN CHALLENGING LOCATIONS

Background and Aim: Polyps located at certain locations are difficult to resect and are usually referred to surgery due to concern for incomplete resection or adverse events. However, surgery is associated with significant risks. Our study aimed to assess the efficacy and safety of endoscopic resection of colorectal polyps in challenging locations.

Author commentary on Ina B. Pedersen et al.

Ina B. Pedersen et al. Incomplete endoscopic resection of colorectal polyps: a prospective quality assurance study

Prophylactic clips to reduce delayed polypectomy bleeding after resection of large colorectal polyps: a systematic review and meta-analysis of randomized trials

Prophylactic clips to prevent delayed polypectomy bleeding (DPB) after endoscopic resection of large colorectal polyps remains controversial. We performed a systematic review and meta-analysis to evaluate the efficacy of prophylactic clips for preventing DPB by synthesizing the results of randomized trials. PubMed, Cochrane Library, and EMBASE were searched to October 2019 to identify randomized controlled trials evaluating the efficacy of placing prophylactic clips to reduce DPB after resection of large (≥10mm) colorectal polyps. The primary outcome was DPB defined by GI bleeding after the conclusion of the colonoscopy. Eight studies (n= 3415) met the study criteria, all with a low risk of bias. The overall pooled incidence of DPB was 3.9% (95% confidence interval [CI], 2.4%-5.4%) in patients receiving endoscopic resection of colorectal polyps≥10mm. Placing prophylactic clips reduced DPB in patients receiving prophylactic clips (relative risk [RR], 0.61; 95% CI, 0.43-0.85; I2= 37.8%) compared with no clips with a number needed to treat (NNT) of 52 (95% CI, 31-163). In stratified analyses, placing clips was associated with reduced risks of DPB in patients with polyps≥20mm (RR, 0.54; 95% CI, 0.35-0.84; I2= 0.0%; NNT, 30), nonpedunculated morphology (RR, 0.54; 95% CI, 0.36-0.81; I2= 0.0%; NNT, 39), and located proximal to the hepatic flexure (RR, 0.49; 95% CI, 0.31-0.78; I2= 54.8%; NNT, 25) compared with no clips. Prophylactic clips after endoscopic resection of colorectal polyps≥10mm demonstrated a modest reduction in the risk of DPB. Larger reductions were observed in patients with polyps≥20mm, nonpedunculated morphology, or located proximal to the hepatic flexure.

S0973 Outcomes of en-bloc vs Piecemeal Endoscopic Resection for Colorectal Polyps With High-Grade Dysplasia or Intramucosal Cancer

INTRODUCTION: Benign colorectal polyps with high grade dysplasia (HGD) or intramucosal cancer (ImCA) are often large and can be completely removed by endoscopic resection (ER). However, malignant recurrence after ER of HGD/ImCA has been described in Asian literature, which is of significant concern. Also, it is uncertain whether type of ER (piecemeal vs. en-bloc) for HGD/ImCA impacts clinical outcomes. We evaluated the short- and long-term outcomes of endoscopic resection of colorectal polyps with HGD/ImCA. METHODS: Retrospective chart review was performed to identify patients who underwent ER for colorectal polyps with HGD/ImCA in two academic medical centers from 2005 to 2019. Clinical, endoscopic, and pathological characteristics of all patients were extracted. To adjust for potential censoring bias, Competing-Risk Regression was performed to estimate the benign recurrence as malignant lesions were counted as a competing risk due to surgical referrals with no follow-up procedures. RESULTS: A total of 196 patients with HGD/ImCA lesions were included; 66 (33.6%) were resected en bloc and 130 (66.3%) piecemeal. Polyps resected by piecemeal ER (p-ER) were larger in size (22.8 vs. 15.1 mm, P < 0.0001), sessile in morphology (P < 0.0001), and right-sided in location (P < 0.0001) compared to en-bloc [Table 1]. 17 (8.6%) patients were referred for surgery after index colonoscopy, all after p-ER. Adverse events occurred in 4 patients (3 delayed bleeding and 1 post polypectomy syndrome). 126 (64%) patients entered surveillance colonoscopy. A total of 31 recurrences occurred over a mean follow-up period of 21 months. Benign recurrences were 11 times (HR = 10.8, 95% CI: 1.5–78.9; P = 0.019) more likely in p-ER than en-bloc group [Figure 1A]. HGD/malignant recurrence occurred in 4/31 patients, all among p-ER (log-rank P = 0.132) with the number needed to treat to prevent 1 malignant recurrence 4.9 (95% CI 2.8–19.2) [Figure 1B]. All these patients were referred for surgery. 26/31 (84%) underwent repeat ER. Of these, 8/26 (30.7%) had successful ER without any further recurrence, and 5/26 (19%) still had residual adenoma despite repeated ER attempts after a mean of 1.9 ± 0.79 procedures, and 2/26 died of unrelated reasons. CONCLUSION: Piecemeal resection of polyps with HGD/ImCA resulted in higher proportion of malignant recurrence and surgical referral compared to en-bloc resection. Thus, en-bloc resection should be preferred for these lesions whenever technically feasible.Table 1.: Baseline characteristics for all included patientsFigure 1.: A: Risk of adenoma recurrence. B: Risk of advanced adenoma and malignant recurrence.

Incomplete endoscopic resection of colorectal polyps: a prospective quality assurance study.

Endoscopic screening with polypectomy has been shown to reduce colorectal cancer incidence in randomized trials. Incomplete polyp removal and subsequent development of post-colonoscopy cancers may attenuate the effect of screening. This study aimed to quantify the extent of incomplete polyp removal. We included patients aged 50-75 years with nonpedunculated polyps ≥ 5 mm removed during colonoscopy at four hospitals in Norway. To evaluate completeness of polyp removal, biopsies from the resection margins were obtained after polypectomy. Logistic regression models were fitted to identify factors explaining incomplete resection. 246 patients with 339 polyps underwent polypectomy between January 2015 and June 2017. A total of 12 polyps were excluded due to biopsy electrocautery damage, and 327 polyps in 246 patients (mean age 67 years [range 42-83]; 52 % male) were included in the analysis. Overall, 54 polyps (15.9 %) in 54 patients were incompletely resected. Histological diagnosis of the polyp (sessile serrated lesions vs. adenoma, odds ratio [OR] 10.9, 95 % confidence interval [CI] 3.9-30.1) and polyp location (proximal vs. distal colon, OR 2.8, 95 %CI 1.0-7.7) were independent risk factors for incomplete removal of polyps 5-19 mm. Board-certified endoscopists were not associated with lower rates of incomplete resection compared with trainees (14.0 % vs. 14.2 %), OR 1.0 (95 %CI 0.5-2.1). Incomplete polyp resection was frequent after polypectomy in routine clinical practice. Serrated histology and proximal location were independent risk factors for incomplete resection. The performance of board-certified gastroenterologists was not superior to that of trainees.

Magnification endoscopy in combination with acetic acid enhancement and narrow-band imaging for the accurate diagnosis of colonic neoplasms.

Background and study aims Magnification endoscopy with narrow-band imaging (NBIME) and NBIME with acetic acid enhancement (A-NBIME) enable visualization of the vascular and microstructural patterns of colorectal polyp. We compared the diagnostic accuracy and reproducibility of white light endoscopy (WLE), NBIME, and A-NBIME for predictive histologic diagnosis. Patients and methods Consecutive colorectal polyps (N = 628; 38 hyperplasias, 488 adenomas, 72 M-SM1 cancers, and 30 SM2 cancers) were photographed with WLE, NBIME, and A-NBIME. Endoscopic images were independently reviewed by three experts, according to the traditional criteria for WLE, the Japan NBI Expert Team classification for NBIME, and pit pattern classification for A-NBIME to compare diagnostic accuracy and interobserver diagnostic agreement among modalities. Results The specificity (95 % confidence interval) of hyperplasia and SM2 cancer with WLE were 98.2 % (96.8 %–99.1%) and 99.4 % (98.5 %–99.9 %), respectively, showing high accuracy for endoscopic resection without magnifying observation. Diagnostic accuracy of WLE, NBIME, and A-NBIME was 80.8 % (77.4 %–83.8 %), 79.3 % (75.9 %–82.4 %), and 86.1 % (83.2 %–88.7 %), respectively, showing the highest accuracy for A-NBIME among modalities ( P < .05). NBIME showed a lower PPV for M-SM1 cancer ( P < .05), as with WLE ( P = .08) compared to A-NBIME. Fleiss’s kappa values for WLE, NBIME, and A-NBIME diagnosis were 0.43 (0.39 – 0.46), 0.52 (0.49 – 0.56) and 0.65 (0.62 – 0.69), respectively, showing insufficient reproducibility of WLE and superiority of A-NBIME among modalities. Conclusion WLE showed high accuracy for endoscopic resection of colorectal polyps in expert diagnosis. NBIME demonstrated a higher diagnostic reproducibility than WLE. A-NBIME showed possible superiority among modalities in both diagnostic accuracy and reproducibility.

Efficacy and safety of three different endoscopic methods in treatment of 6–20 mm colorectal polyps

Objective: Endoscopic resection of colorectal polyps is widely established as the optimal method to manage precancerous lesions. But the optimal technique for removal of the polyps is uncertain. The aim of this study was to compare the efficacy and safety of three methods for the management of 6–20mm colorectal polyps.Methods: A prospective, randomised controlled trial was conducted at the 900TH Hospital of Joint Logistics Support Force in Fujian, China. Endoscopically diagnosed colorectal polyps, 6–20 mm in size, were randomly assigned to the cold snare polypectomy (CSP), cold snare endoscopic mucosal resection (CS-EMR) or endoscopic mucosal resection (EMR) group. After polypectomy, additional 3–5 forceps biopsies by leading narrow-band imaging (NBI) were performed at the base and margins of polypectomy sites to assess the presence of residual polyp tissue and all samples were sent for histopathological analysis to assess completeness of resection. Polypectomy timing, tissue retrieval and complications were recorded at the time of the procedure.Results: A total of 781 polyps in 404 patients were assessed and randomly assigned to each group. Of these, 763 polyps were finally analyzed based on the pathology results. The complete resection rates with CSP, CS-EMR and EMR were 81.6%, 94.1% and 95.5%, respectively (p < .001). The intraprocedural bleeding rate, immediately after polypectomy, was significantly higher in the CSP group than in the CS-EMR and EMR group (9.4% vs. 4.4% vs. 1.9%; p < .001). However,delayed bleeding was higher in the EMR group than in the CSP and CS-EMR group (2.6% vs. 1.2% vs. 0.8%, respectively; p = .215). In the multivariate analysis showed that the operation method, lesion size, morphology and the number of resection were independent risk factors for complete resection rate (CRR) (p < .05), but the location and pathological classification of polyps had no significant influence on CRR.Conclusions: CS-EMR is safe and effective in the treatment of 6–20 mm colorectal polyps. Especially for 6–15 mm non-pedunculated polyps, CS-EMR has a high histological complete resection rate comparable to EMR, and retains the low risk of delayed complications after polypectomy with cold snare. CS-EMR is expected to become a more valuable new cold-cutting technique after cold snare polypectomy.

Delayed hemorrhage after cold and hot snare resection of colorectal polyps: a multicenter randomized trial (interim analysis).

Background and study aims Delayed bleeding is believed to occur less frequently after cold snare polypectomy (CSP), but this has not been validated in clinical trials. This study aimed to compare rates of delayed bleeding after CSP and hot snare polypectomy (HSP). Patients and methods We conducted a multicenter, randomized controlled trial. Participants scheduled to undergo endoscopic resection of colorectal polyps ≤ 10 mm were enrolled and randomly assigned to CSP or HSP. Prophylactic clipping was performed at the endoscopists’ discretion. The primary outcome was delayed bleeding rate. Secondary outcomes included immediate bleeding rate and clipping rate. Sample size calculation showed that 451 patients were required in each arm. Results At the end of the study period decided in advance, 308 participants were recruited and an interim analysis was performed. A total of 273 patients (mean age 62.2 ± 8.8 years; 188 males) were analyzed, with 139 patients allocated to CSP and 134 to HSP. In total, 367 polyps were resected with CSP and 360 polyps with HSP. There were no significant differences in patient demographics or polyp characteristics. In per-patient-based analysis, delayed bleeding rates were 0.7 % after CSP and 0.7 % after HSP. Per-polyp analysis showed similar results (CSP: 0.3 % vs. HSP: 0.6 %). The immediate bleeding rate was significantly higher with CSP vs. HSP (54 % vs.14 %, P < 0.0001), while clipping rates were 18 % and 19 %, respectively. Conclusion This interim analysis did not demonstrate that delayed bleeding after CSP is less frequent than after HSP. The delayed bleeding rate after HSP was lower than expected. Meeting presentations: Digestive Disease Week 2017

Strategy choice for endoscopic resection of colorectal polyps in the Russian Federation: results of focal interviewing

Strategy choice for endoscopic resection of colorectal polyps in the Russian Federation: results of focal interviewing

Sa1032 Appropriate and Safe Management of Direct Oral Anticoagulants in Endoscopic Resection of Colorectal Polyps

Sa1032 Appropriate and Safe Management of Direct Oral Anticoagulants in Endoscopic Resection of Colorectal Polyps

Sa1005 Does Restarting Novel Oral Anticoagulants Increase the Clinical Risk of Delayed Bleeding after Endoscopic Resection of Colorectal Polyps?

Sa1005 Does Restarting Novel Oral Anticoagulants Increase the Clinical Risk of Delayed Bleeding after Endoscopic Resection of Colorectal Polyps?

Endoscopic resection of colorectal polyps in patients on antiplatelet therapy: an evidence-based guidance for clinicians.

Due to the rising prevalence of coronary heart disease, endoscopists are more frequently performing a polypectomy in patients on antiplatelet therapy (APT) and dual antiplatelet therapy (DATP). Despite the availability of several guidelines with regard to the management of antiplatelet drugs during the periprocedure period, there is still variability in the current clinical practice. This may be influenced by the low quality of the evidence supporting recommendations, because most of the studies dealing with APT and polypectomy are observational and retrospective, and include mainly small (< 10 mm) polyps. However, some recommendations can still be made. An estimation of the bleeding and thrombotic risk of the patient should be made in advance. In the case of DAPT the procedure should be postponed, at least until clopidogrel can be safely withheld. If possible, non-aspirin antiplatelet drugs should be withheld 5-7 days before the procedure. Polyp size is the main factor related with post-polypectomy bleeding and it is the factor that should drive clinical decisions regarding the resection method and the use of endoscopic prophylactic measures. Non-aspirin antiplatelet agents can be reintroduced 24-48 hours after the procedure. In conclusion, there is little data with regard to the management of DAPT in patients with a scheduled polypectomy. Large randomized controlled trials are needed to support clinical recommendations.

High incidence of metachronous advanced adenoma and cancer after endoscopic resection of colon polyps ≥20 mm in size.

There are limited studies on incidence rates of metachronous neoplastic lesions after resecting large colorectal polyps. In the present study, we analyzed metachronous lesions after endoscopic resection of colorectal polyps ≥20 mm in size. We retrospectively analyzed consecutive patients who underwent endoscopic resection of polyps from 2006 to 2013 at two affiliated hospitals. All patients underwent at least two total colonoscopies before follow up to ensure minimal missed polyps. Only patients who had follow-up colonoscopy annually after resection were recruited. We separated patients according to size of polyp resected; there were 239 patients in the ≥20-mm group and 330 patients in the <20-mm group. Clinical characteristics and cumulative rates of metachronous advanced adenoma and cancer in both groups were analyzed. Advanced adenoma was defined as a neoplastic lesion ≥10 mm in size and adenoma with a villous component. Cumulative rate of development of metachronous advanced adenoma and cancer in the ≥20-mm group was significantly higher than in the <20-mm group (22.9% vs. 9.5%, P < 0.001) at 36 months. There was also more development of small polyps 5-9 mm in the ≥20-mm group than in the <20-mm group (45.2% vs. 28.8%, P < 0.001). With respect to metachronous lesions, there were more right-sided colonic lesions in the ≥20-mm group than in the <20-mm group (78.8% vs. 50.0%, P = 0.015). High incidence rates of development of metachronous neoplastic lesions were detected after resection of colorectal polyps ≥20 mm in size.