INTRODUCTION:Index colonoscopy findings can affect surveillance decisions that have an impact on the future risk of colorectal cancer (CRC). However, the effectiveness of surveillance colonoscopy in reducing CRC risk remains unclear. The aim of this study was to evaluate whether the timing of the first surveillance colonoscopy affected CRC incidence rates. METHODS:We conducted a retrospective cohort study at 2 community endoscopy clinics between 2005 and 2021, including 20,397 individuals. Based on the findings at index colonoscopy, we categorized into 4 groups: advanced adenoma (AA), ≥3 non-AAs, 1-2 non-AAs, and no adenoma. We compared the cumulative incidence of CRC among these groups, focusing on whether the first surveillance interval was less than or greater than 3 years after index colonoscopy. RESULTS:Index colonoscopy findings identified 11,601 subjects with no adenoma, 5,288 with 1-2 non-AA, 1,484 with ≥3 non-AA, and 2,024 with AA. There were 50 cases of CRC: 23 in the no adenoma, 10 in the 1-2 non-AA, 6 in the ≥3 non-AA, and 11 in the AA group. First surveillance after 3 years was associated with a higher incidence of subsequent CRC in the AA group (hazard ratio 3.49, 95% confidence interval 1.06-11.46, P = 0.04). DISCUSSION:In the AA group, surveillance colonoscopy within 3 years was associated with a lower risk of CRC. These findings suggest that a first surveillance within 3 years is particularly effective in subjects with AA.

Research and development of artificial intelligence (AI) in the field of gastrointestinal endoscopy is progressing rapidly. In Japan alone, there are more than 10 AI-assisted endoscopic medical devices that have received regulatory approval, and numerous randomized controlled trials have been published both domestically and internationally. However, the adoption of AI in clinical practice has not been smooth due to factors such as insufficient evaluation of the balance between clinical benefits and harms, unclear cost-effectiveness, the lack of reliable guidelines, and the absence of established reimbursement systems for medical fees. Considering this situation, the Japan Gastroenterological Endoscopy Society (JGES) presents its perspective on the status of AI in endoscopic practice in the form of the following position statements. This comprises nine statements developed by the JGES AI Committee in collaboration with a diverse panel of members. These statements comprehensively address issues related to the quality of endoscopic examinations, cost-effectiveness, clinical disadvantages, preparatory knowledge, medical safety, and legal responsibilities. They have been developed to be practical and useful in actual endoscopy settings.

Research and development of artificial intelligence (AI) in the field of gastrointestinal endoscopy is progressing rapidly. In Japan alone, there are more than 10 AI-assisted endoscopic medical devices that have received regulatory approval, and numerous randomized controlled trials have been published both domestically and internationally. However, the adoption of AI in clinical practice has not been smooth due to factors such as insufficient evaluation of the balance between clinical benefits and harms, unclear cost-effectiveness, the lack of reliable guidelines, and the absence of established reimbursement systems for medical fees. Considering this situation, the Japan Gastroenterological Endoscopy Society (JGES) presents its perspective on the status of AI in endoscopic practice in the form of the following position statements. This comprises nine statements developed by the JGES AI Committee in collaboration with a diverse panel of members. These statements comprehensively address issues related to the quality of endoscopic examinations, cost-effectiveness, clinical disadvantages, preparatory knowledge, medical safety, and legal responsibilities. They have been developed to be practical and useful in actual endoscopy settings.

INTRODUCTION:This study investigated the detection rate of colorectal neuroendocrine neoplasms (NENs) using large-scale colonoscopy data. METHODS:This cross-sectional analysis used large-scale data from a Japanese multicenter observational study of colonoscopies performed from 2010 to 2020. RESULTS:Among 82,005 colonoscopy cases, colorectal NENs were identified in 71 (67 of which were neuroendocrine tumors), with a detection rate of 0.087% (95% confidence interval: 0.069-0.109). Most were small rectal lesions, with only 4 >10 mm in size and 3 located in the colon. DISCUSSION:The detection rate of colorectal NENs during colonoscopy is substantially higher than expected.

BACKGROUND AND AIM:The risk of colorectal cancer among fecal immunochemistry test-positive individuals who had undergone previous colonoscopies remains unclear. Therefore, this study aimed to determine the differences in the risk of colorectal cancer among fecal immunochemistry test-positive individuals according to the timing of their previous colonoscopies. METHODS:This multicenter, retrospective, observational study was conducted in Japan as a subgroup analysis of the J-SCOUT study (UMIN000040690), which integrated and analyzed a database comprising all colonoscopies performed at participating Japanese institutions between 2010 and 2020. This study used colonoscopy data of fecal immunochemistry test-positive individuals aged ≥ 20 years from three facilities that entered the timing of previous colonoscopies into the endoscopy database. Histologically confirmed advanced neoplasia was the study's primary outcome. Multivariate logistic regression analysis was used to calculate the odds ratios for each variable. RESULTS:In total, 11,143 fecal immunochemistry test-positive patients underwent colonoscopy during the study period. Of these, 10,160 patients were included in the analysis after excluding those who met the exclusion criteria. The overall advanced neoplasia detection rate was 9.38% (953/10,160; 95% confidence interval: 8.82-9.96%). Compared with the first colonoscopy, the odds ratios for advanced neoplasia in individuals who underwent colonoscopies 1, 2, 3, 4, 5, > 5, and ≥ 10 years previously were 0.27, 0.15, 0.06, 0.10, 0.29, 0.31, and 0.31, respectively. CONCLUSIONS:The detection rates of advanced neoplasia were low among the fecal immunochemistry test-positive individuals who had undergone colonoscopy, particularly in the past 5 years.

The article by Sekiguchi et al.1 shows that there is a reality of opportunities for detecting colorectal cancers (CRCs) by a prospective case study with questionnaires of consecutive CRC patients at multiple hub hospitals for cancer treatment. More than thousands of CRC patients were collected within only 1 year. Huge numbers of CRCs would help the comparisons of backgrounds of detected CRCs, even though they were only case studies, essentially. This study showed that nonscreening-detected CRC occupied more than 60% of CRCs, which may indicate that CRC screening in Japan does not function well. A US study found that the screening rate reached 71.8% of citizens aged 50–75 in 2021 and was promoted up to 74.4% as a "healthy people 2030 target."2 The increase in screening-detected CRC would also be one of the successful indicators of screening projects in the real world. The screening-detected CRCs critically showed less advanced invasions compared with nonscreening-detected CRCs in this article, too. The other important issue is several types of interval CRC (iCRC). First of all, CRC detected within 1 year after positive fecal immunochemical test (FIT) with noncompliance to colonoscopy showed more advanced features, such as more invasions, metastasis, and more invasive treatment, as well as the tendency with left side by location and male by sex, which were more similar with symptomatic CRC, compared with FIT-iCRC, which is defined as CRC detected after a negative FIT and before the next recommended test is due and 3-year postcolonoscopy CRC (PCCRC-3 yr), which is defined as CRC diagnosed within 3 years after a colonoscopy with no cancer. These findings emphasize that the patients with FIT-positive results should be treated cautiously and quickly, and that the high quality of the colonoscopy procedure should be performed to prevent FIT-iCRC and PCCRC-3 yr. FIT-iCRC and PCCRC-3 yr showed a nonnegligible proportion of detected CRCs and a higher proportion of BRAF mutations, which may include different biological features than other types of CRCs. In addition, these findings indicate that serrated lesions and nonpolypoid lesions, such as laterally spreading tumor, are one of the major candidates for interval cancers.3 These lesions would be needed to investigate the nature of progression. This study collected huge numbers of CRCs, which may confirm generalizability. Fundamentally, the study design was prospective, and also a consecutive case study in major hub cancer treatment hospitals, which may include some bias. The history of previous findings of colonoscopies in addition to intervals and a history of FIT and colonoscopy also may influence the prevalence of interval cancers. Probably, the next step would be to clarify the magnitude of interval cancer in daily practices by using big real-world data, including control data, which would verify the real proportions of FIT-iCRC and PCCRC-3 yr and their biological and clinical characteristics. The author declares no conflict of interest for this article. None.

Objectives Colonoscopy withdrawal times are associated with the adenoma detection rate (ADR). However, the relationship between ADR and cecal insertion time has been inadequately characterized. We aimed to evaluate endoscopist‐related factors involved in the ADR, including the average individual colonoscopy insertion and withdrawal times. Methods This observational study used a colonoscopy database with pathology data from routine clinical practice in Japanese institutions. The odds ratios (OR) of endoscopist‐related factors related to ADRs were examined using a generalized linear mixed model. Results Of the 186,293 colonoscopies performed during the study period, 47,705 colonoscopies by 189 endoscopists in four hospitals were analyzed for ADR. The overall ADR was 38.3% (95% confidence interval [CI] 37.8, 38.7). Compared to endoscopists with mean cecal insertion times of <5 min, the OR of ADR for those with mean cecal insertion times of 5–9, 10–14, and ≥15 min were 0.84 (95% CI 0.71, 0.99), 0.68 (95% CI 0.52, 0.90), and 0.45 (95% CI 0.25, 0.78), respectively. Compared to endoscopists with mean withdrawal times of <6 min, the OR of ADR for those with mean withdrawal times of 6–9, 10–14, and ≥15 min were 1.38 (95% CI 1.03, 1.85), 1.48 (95% CI 1.09, 2.02), and 1.68 (95% CI 1.04, 2.61), respectively. There were no significant differences in ADRs by endoscopist specialty, gender, or the total number of examinations performed. Conclusion Individual mean colonoscopy insertion time was associated with ADR and might be considered as a colonoscopy quality indicator as well as withdrawal time.

OBJECTIVES:To examine whether reasonable detection rate of endoscopically diagnosed lesions as adenoma ("endoscopic" adenoma detection rate [ADR]) could be calculated with a database generated from colonoscopy reports and whether it could be used as a surrogate colonoscopy quality indicator of "pathological" ADR. METHODS:A lesion-by-lesion database of colonoscopies performed between 2010 and 2020 at eight Japanese endoscopy centers and corresponding pathology database were integrated. Differences in numbers of detected polyps, "endoscopic" and "pathological" adenomas, and what these differences could be attributed to were examined. Polyp detection rate (PDR), "endoscopic" and "pathological" ADRs, and correlation coefficients between "pathological" ADR and PDR or "endoscopic" ADR by each endoscopist were calculated. RESULTS:Overall, 129,065 colonoscopy reports were analyzed. Among a total of 146,854 polyps, more "endoscopic" adenomas (n = 117,359) were observed than "pathological" adenomas (n = 70,076), primarily because adenomas were not resected on site, rather than because of a misdiagnosis. In all patients analyzed, PDR, "endoscopic" and "pathological" ADRs were 56.4% (95% confidence interval [CI] 56.2-56.7), 48.0% (95% CI 47.7-48.3), and 32.7% (95% CI 32.5-33.0), respectively. "Endoscopic" and "pathological" ADRs from each endoscopist showed a high correlation in hospitals where adenomas were usually resected at the time of examination. CONCLUSIONS:By appropriately describing endoscopically diagnosed lesions as "adenomas" in endoscopy reports, "endoscopic" ADR might be used as a surrogate colonoscopy quality indicator of "pathological" ADR (UMIN000040690).

BACKGROUND & AIMS: To date, no regional evidence of long-term colorectal cancer (CRC) risk reduction after endoscopic premalignant lesion removal has been established. We aimed to analyze this over a longterm follow-up evaluation. METHODS: This was a prospective cohort study of participants from the Japan Polyp Study conducted at 11 Japanese institutions. Participants underwent scheduled follow-up colonoscopies after a 2 -round baseline colonoscopy process. The primary outcome was CRC incidence after randomization. The observed/expected ratio of CRC was calculated using data from the population -based Osaka Cancer Registry. Secondary outcomes were the incidence and characteristics of advanced neoplasia (AN). RESULTS: A total of 1895 participants were analyzed. The mean number of follow-up colonoscopies and the median follow-up period were 2.8 years (range, 1-15 y) and 6.1 years (range, 0.8-11.9 y; 11,559.5 person -years), respectively. Overall, 4 patients (all males) developed CRCs during the study period. The observed/expected ratios for CRC in all participants, males, and females, were as follows: 0.14 (86% reduction), 0.18, and 0, respectively, and 77 ANs were detected in 71 patients (6.1 per 1000 person -years). Of the 77 ANs detected, 31 lesions (40.3%) were laterally spreading tumors, nongranular type. Nonpolypoid colorectal neoplasms (NP-CRNs), including flat (<10 mm), depressed, and laterally spreading, accounted for 59.7% of all detected ANs. Furthermore, 2 of the 4 CRCs corresponded to T1 NP-CRNs. CONCLUSIONS: Endoscopic removal of premalignant lesions, including NP-CRNs, effectively reduced CRC risk. More than half of metachronous ANs removed by surveillance colonoscopy were NP-CRNs. The Japan Polyp Study: University Hospital Medical Information Network Clinical Trial Registry: University Hospital Medical Information Network Clinical Trial Registry, C000000058; cohort study: UMIN000040731.

This is the first report from a multicenter prospective cohort study of colorectal neuroendocrine tumor (NET), the C-NET STUDY, conducted to assess the long-term outcomes of the enrolled patients. This report aimed to elucidate the clinicopathological features of the enrolled patients and lesions. Colorectal NET patients aged 20–74 years were consecutively enrolled and followed up at 50 institutions. The baseline characteristics and clinicopathological findings at enrollment and treatment were assessed. A total of 495 patients with 500 colorectal NETs were included. The median patient age was 54 years, and 85.3% were asymptomatic. The most frequent lesion location was the lower rectum (88.0%); 99.4% of the lesions were clinically diagnosed to be devoid of metastatic findings, and 95.4% were treated with endoscopic resection. Lesions < 10 mm comprised 87.0% of the total, 96.6% had not invaded the muscularis propria, and 92.6% were classified as WHO NET grade 1. Positive lymphovascular involvement was found in 29.2% of the lesions. Its prevalence was high even in small NETs with immunohistochemical/special staining for pathological assessment (26.4% and 40.9% in lesions sized < 5 mm and 5–9 mm, respectively). Among 70 patients who underwent radical surgery primarily or secondarily, 18 showed positive lymph node metastasis. The characteristics of real-world colorectal NET patients and lesions are elucidated. The high positivity of lymphovascular involvement in small NETs highlights the necessity of assessing the clinical significance of positive lymphovascular involvement based on long-term outcomes, which will be examined in later stages of the C-NET STUDY. UMIN000025215.

Risk stratification by index colonoscopy is well established for first surveillance endoscopy, but whether the previous two colonoscopies affect the subsequent advanced neoplasias has not been established. Therefore, the subsequent risk based on the findings of the index and first surveillance colonoscopies were investigated. This retrospective, cohort study was conducted in two clinics and included participants who had undergone two or more colonoscopies after index colonoscopy. High-risk was defined as advanced adenoma (≥ 1 cm, or tubulovillous or villous histology, or high-grade dysplasia). Based on the findings of the index and first surveillance colonoscopies, patients were classified into four categories: category A (both colonoscopy findings were normal), category B (no high-risk findings both times), category C (one time high-risk finding), and category D (high-risk findings both times). The incidence of subsequent advanced neoplasia was examined in each category. A total of 13,426 subjects were included and surveyed during the study periods. The subjects in category D had the highest risk of advanced neoplasia (27.4%, n = 32/117). The subjects in category A had the lowest risk (4.0%, n = 225/5,583). The hazard ratio for advanced neoplasia of category D compared to category A was 9.90 (95% Confidence interval 6.82–14.35, P<0.001). Classification based on the findings of index and first surveillance colonoscopies more effectively stratifies the risk of subsequent advanced neoplasia, resulting in more proper allocation of colonoscopy resources after two consecutive colonoscopies.

ObjectiveTo assess whether follow-up colonoscopy after polypectomy at 3 years only, or at 1 and 3 years would effectively detect advanced neoplasia (AN), including nonpolypoid colorectal neoplasms (NP-CRNs).DesignA prospective multicentre randomised controlled trial was conducted in 11 Japanese institutions. The enrolled participants underwent a two-round baseline colonoscopy (interval: 1 year) to remove all neoplastic lesions. Subsequently, they were randomly assigned to undergo follow-up colonoscopy at 1 and 3 years (2-examination group) or at 3 years only (1-examination group). The incidence of AN, defined as lesions with low-grade dysplasia ≥10 mm, high-grade dysplasia or invasive cancer, at follow-up colonoscopy was evaluated.ResultsA total of 3926 patients were enrolled in this study. The mean age was 57.3 (range: 40–69) years, and 2440 (62%) were male. Of these, 2166 patients were assigned to two groups (2-examination: 1087, 1-examination: 1079). Overall, we detected 29 AN in 28 patients at follow-up colonoscopy in both groups. On per-protocol analysis (701 in 2-examination vs 763 in 1-examination group), the incidence of AN was similar between the two groups (1.7% vs 2.1%, p=0.599). The results of the non-inferiority test were significant (p=0.017 in per-protocol, p=0.001 in intention-to-treat analysis). NP-CRNs composed of dominantly of the detected AN (62%, 18/29), and most of them were classified into laterally spreading tumour non-granular type (83%, 15/18).ConclusionAfter a two-round baseline colonoscopy, follow-up colonoscopy at 3 years detected AN, including NP-CRNs, as effectively as follow-up colonoscopies performed after 1 and 3 years.

Background and Aim In Japan, risk stratification after baseline colonoscopy is not widely accepted. We investigated the findings of baseline colonoscopies at 17 community practices and evaluated the risk of the incidence of advanced neoplasia over a 5-year period. Methods This retrospective cohort study enrolled 3115 subjects over 40 years of age who underwent baseline colonoscopies and had at least one repeated colonoscopy within 5 years. Each group was classified based on the endoscopic findings of the baseline colonoscopy: no neoplasia/diminutive polyp <5 mm (N/D); small adenoma <10 mm; advanced adenoma; invasive cancer, respectively. We examined the incidence of advanced neoplasia during these 5 years and investigated the relationship between the surveillance colonoscopy and newly detected advanced neoplasia. Results The small adenoma group did not show any significant increased risk as compared to the N/D group (hazard ratio [HR]: 0.799. 95% CI 0.442-1.443). There was a significantly increased risk in the advanced adenoma and invasive cancer groups (HR: 4.996, 95% CI 2.940-8.491, HR: 3.737, 95% CI 1.309-10.666). Cancer incidences during the study period were 0.18% in the N/D group, and 1.9% in the invasive cancer group, respectively. Undergoing surveillance colonoscopies twice within 5 years decreased the risk of advanced neoplasia. Conclusions There was a close relationship between the endoscopic findings of baseline colonoscopies and subsequent advanced neoplasia development. Risk stratification for advanced neoplasia based on the baseline findings can serve as a useful index for determining the optimal interval and frequency of colonoscopies over a 5-year period.

BACKGROUND AND AIM:Right colon polyps can especially be overlooked when they are located on the backs of haustral folds. Previous studies have reported that repeated forward-view examinations in the right colon were effective in reducing adenoma miss rates. The aim of this study was to clarify the impact of retroflexion in the right colon after repeated forward-view examinations. METHODS:This multicenter, prospective, observational study was conducted at three institutions in Kumamoto, Japan, between February 2014 and December 2015. Subjects who were over 40 years old and scheduled for colonoscopy were recruited. For the forward view, after cecal intubation, the colonoscope was withdrawn to the hepatic flexure. The colonoscope was sequentially reinserted to the cecum and then withdrawn to the hepatic flexure. For the retroflexion view (RV), the colonoscope was reinserted to the cecum, retroflexed, and then withdrawn to the hepatic flexure. All polyps were resected at the time of detection. The primary outcome of this study was the adenoma miss rate for the repeated forward-view examinations. RESULTS:Of the 777 enrolled participants, retroflexion was successful in 730 (94.0%). The repeated forward-view withdrawal technique detected 291 adenomas, while the third withdrawal in the RV detected 53. The adenoma miss rate for the repeated forward-view withdrawal was 15.4%. No severe adverse events occurred during retroflexion. CONCLUSION:Because adenomas located on potential blind spots can be missed when only using forward-view examinations, retroflexion in the right colon after repeated forward-view examinations might improve colonoscopy detection rates.

AIM : Limited evidence exists on the relationship between colonoscopy withdrawal time and adenoma detection rate in Japan. We aimed to clarify the clinical impact of colonoscopy withdrawal time in a Japanese setting. MATERIALS AND METHODS : We recruited 6,919 consecutive patients from four Japanese endoscopic centers between April 2010 and April 2011. Colonoscopists were divided into the following groups based on the median withdrawal time of a negative colonoscopy: <6 min (group A), 6–9 min (group B), and ≥10 min (group C). We analyzed the relationship between these withdrawal time groups and adenoma detection rateusing multiple logistic regression analysis. RESULTS : The final analysis included 3,862 patients. Group A included 201 (3 colonoscopists), group B included 2,741 (13 colonoscopists), and group C included 920patients (9 colonoscopists). We found that adenoma detection rates tended to increase with longer median negative colonoscopy withdrawal times ( p <0.01). Compared with group A, the odds ratios in group B and group C were 1.98 (95% confidence interval [CI], 1.42–2.76) and 2.51 (95% CI, 1.68–3.75), respectively. CONCLUSIONS : A colonoscopy withdrawal time of over 6 min appears to be a quality indicator for colonoscopy even in a Japanese setting.

Risk stratification after baseline colonoscopy is considered necessary for adequate surveillance intervals in Japan. To address this issue, we clarified the risk of colorectal neoplasia development based on the findings of the baseline colonoscopy in five years at 18 community practices.

Colonoscopy is less effective in preventing colorectal cancer in the proximal compared with the distal colon. Proximal colon polyps would be missed especially when located on the backs of haustral folds and the inner curve of flexures. Previous report showed that tandem observation with forward view is effective to reduce polyp miss rates, but it is unclear whether all polyps are detectable with tandem forward view. Aim of this study was to clarify the impact of the retroflection in the proximal colon after tandem observation with high-definition, wide-angle colonoscopy.