Postcolonoscopy Colorectal Cancer in Sweden From 2003 to 2012: Survival, Tumor Characteristics, and Risk Factors

Type 2 diabetes mellitus and post-colonoscopy colorectal cancer: clinical and molecular characteristics and survival

PURPOSE

Studies suggest that patients with type two diabetes mellitus (T2D) may be at increased risk of post-colonoscopy colorectal cancer (PCCRC). We investigated clinical and molecular characteristics and survival of T2D patients with PCCRC to elucidate how T2D-related PCCRC may arise.

METHODS

We identified T2D patients with colorectal cancer (CRC) from 1995 to 2015 and computed prevalence ratios (PRs) comparing clinical and molecular characteristics of CRC in T2D patients with PCCRC vs. in T2D patients with colonoscopy-detected CRC (dCRC). We also followed T2D patients from the diagnosis of PCCRC/dCRC until death, emigration, or study end and compared mortality using Cox-proportional hazards regression models adjusted for sex, age, year of CRC diagnosis, and CRC stage.

RESULTS

Compared with dCRC, PCCRC was associated with a higher prevalence of proximal CRCs (54% vs. 40%; PR: 1.43, 95% confidence interval [CI] 1.27-1.62) in T2D patients. We found no difference between PCCRC vs. dCRC for CRC stage, histology, and mismatch repair status. The proportion of CRCs that could be categorized as PCCRC decreased over time. Within one year after CRC, 63% of PCCRC vs. 78% of dCRC patients were alive (hazard ratio [HR] 1.85 [95% CI 1.47-2.31]). Within five years after CRC, 44% of PCCRC vs. 54% of dCRC patients were still alive (HR 1.44 [95% CI 1.11-1.87]).

CONCLUSION

The increased prevalence of proximally located PCCRCs and the poorer survival may suggest overlooked colorectal lesions as a predominant explanation for T2D-related PCCRC, although altered tumor progression cannot be ruled out.

Lead Time and Immortal Time Biases Impact the Calculation of Post-colonoscopy Colorectal Cancer Survival

The World Endoscopy Organization (WEO) standardized the reporting of post-colonoscopy colorectal cancers (PCCRCs), which account for 7% to 10% of colorectal cancers (CRCs).1 PCCRCs are diagnosed 6 to 36 months after a false negative colonoscopy. Detected CRCs (dCRCs) are diagnosed ≤6 months after an index true positive colonoscopy.2 PCCRC prognosis is unclear, with outcomes reported as comparable,3 superior,4 or inferior5,6 to those of dCRC. Because WEO terminology defines cases relative to the index colonoscopy, conventional survival analyses of PCCRC are susceptible to lead time and immortal time biases. We evaluated the influence of these biases on mortality in a population-based retrospective cohort of 10,938 dCRCs (93.8%) and 717 PCCRCs (6.2%). This study was set within Kaiser Permanente Northern California (KPNC), a large integrated health system, whose members are similar in demographic and socioeconomic characteristics to the Northern California region.7.

Post-colonoscopy colorectal cancers in a national fecal immunochemical test-based colorectal cancer screening program

BACKGROUND

Post-colonoscopy colorectal cancers (PCCRCs) decrease the effect of colorectal cancer (CRC) screening programs. To enable PCCRC incidence reduction in the long-term, we classified PCCRCs diagnosed after colonoscopies performed in a fecal immunochemical test (FIT)-based screening program.

METHODS

PCCRCs diagnosed after colonoscopies performed between 2014-2016 for a positive FIT in the Dutch CRC screening program were included. PCCRCs were categorized according to the World Endoscopy Organization consensus statement into (a) interval PCCRC (diagnosed before the recommended surveillance); (b) non-interval type A (diagnosed at the recommended surveillance interval); (c) non-interval type B (diagnosed after the recommended surveillance interval); or (d) non-interval type C (diagnosed after the intended recommended surveillance interval, with surveillance not implemented owing to co-morbidity). The most probable etiology was determined by root-cause analysis. Tumor stage distributions were compared between categories.

RESULTS

116362 colonoscopies were performed after a positive FIT with 9978 screen-detected CRCs. During follow-up, 432 PCCRCs were diagnosed. The 3-year PCCRC rate was 2.7%. PCCRCs were categorized as interval (53.5%), non-interval type A (14.6%), non-interval type B (30.6%), and non-interval type C (1.4%). The most common etiology for interval PCCRCs was possible missed lesion with adequate examination (73.6%); they were more often diagnosed at an advanced stage (stage III/IV; 53.2%) compared with non-interval type A (15.9%; P<0.001) and non-interval type B (40.9%; P=0.03) PCCRCs.

CONCLUSIONS

The 3-year PCCRC rate was low in this FIT-based CRC screening program. Approximately half of PCCRCs were interval PCCRCs. These were mostly caused by missed lesions and were diagnosed at a more advanced stage. This emphasizes the importance of high quality colonoscopy with optimal polyp detection.

Incidence, characteristics, and predictive factors of post-colonoscopy colorectal cancer

BACKGROUND

Post-colonoscopy colorectal cancer (PCCRC) is colorectal cancer (CRC) diagnosed after a colonoscopy in which no cancer is found.

OBJECTIVE

As PCCRC has become an important quality indicator, we determined its rates, characteristics, and index colonoscopy-related predictive factors.

METHODS

We carried out a multicenter, observational, retrospective study between 2015 and 2018. Rates were calculated for PCCRC developing up to 10 years after colonoscopy. PCCRC was categorized according to the most plausible explanation using World Endoscopy Organization methodology. Our PCCRC population was compared to a control cohort without CRC matched 1:4 by sex, age, index colonoscopy date, indication, endoscopist, and hospital.

RESULTS

One hundred seven PCCRC and 2508 detected CRC were diagnosed among 101,524 colonoscopy (0.1%), leading to rates of 0.4%, 2.2%, 3.1%, and 4.1% at 1, 3, 5, and 10 years, respectively. PCCRC was in right (42.4%), left (41.4%), and transverse (16.4%) colon with 31.5% at stage I, 24.7% stage II, 32.6% stage III, and 11.2% stage IV. Twenty point three percent were classified as incomplete resection, 5.4% as unresected lesions, 48.6% as missed lesions with adequate colonoscopy, and 25.7% as missed lesions with inadequate colonoscopy. The median time from colonoscopy to PCCRC was 42 months. Previous inadequate preparation (OR 3.05, 95%CI 1.73-5.36) and piecemeal polypectomy (OR 19.89, 95%CI 8.67-45.61) were independently associated with PCCRC.

CONCLUSIONS

In our population, 4.1% of CRC cases were PCCRC. Most of these lesions were in right colon and attributable to lesions not visualized despite adequate bowel cleansing. Previous inadequate cleansing and piecemeal polypectomy were associated with PCCRC.

Postcolonoscopy colorectal cancer: Prevalence, categorization and root-cause analysis based on the World Endoscopic Organization system

AIMS

The World Endoscopy Organization (WEO) recommends that endoscopy units implement a process to identify postcolonoscopy colorectal cancer (PCCRC). The aims of this study were to assess the 3-year PCCRC rate and to perform root-cause analyses and categorization in accordance with the WEO recommendations.

PATIENTS AND METHODS

Cases of colorectal cancers (CRCs) in a tertiary care center were retrospectively included from January 2018 to December 2019. The 3-year and 4-year PCCRC rates were calculated. A root-cause analysis and categorization of PCCRCs (interval and type A, B, C noninterval PCCRCs) were performed. The level of agreement between two expert endoscopists was assessed.

RESULTS

A total of 530 cases of CRC were included. A total of 33 were deemed PCCRCs (age 75.8±9.5 years; 51.5% women). The 3-year and 4-year PCCRC rates were 3.4% and 4.7%, respectively. The level of agreement between the two endoscopists was acceptable either for the root-cause analysis (k=0.958) or for the categorization (k=0.76). The most plausible explanations of the PCCRCs were 8 "likely new PCCRCs", 1 (4%) "detected, not resected", 3 (12%) "detected, incomplete resection", 8 (32%) "missed lesion, inadequate examination", and 13 (52%) "missed lesion, adequate examination". Most PCCRCs were deemed noninterval Type C PCCRCs (N=17, 51.5%).

CONCLUSION

WEO recommendations for root-cause analysis and categorization are useful to detect areas for improvement. Most PCCRCs were avoidable and were likely due to missed lesions during an otherwise adequate examination.

Adenoma Detection Rate and Colorectal Cancer Risk in Fecal Immunochemical Test Screening Programs : An Observational Cohort Study

BACKGROUND

Colorectal cancer (CRC) screening programs based on fecal immunochemical tests (FITs) represent the standard of care for population-based interventions. Their benefit depends on the identification of neoplasia at colonoscopy after FIT positivity. Colonoscopy quality measured by adenoma detection rate (ADR) may affect screening program effectiveness.

OBJECTIVE

To examine the association between ADR and postcolonoscopy CRC (PCCRC) risk in a FIT-based screening program.

DESIGN

Retrospective population-based cohort study.

SETTING

Fecal immunochemical test-based CRC screening program between 2003 and 2021 in northeastern Italy.

PATIENTS

All patients with a positive FIT result who had a colonoscopy were included.

MEASUREMENTS

The regional cancer registry supplied information on any PCCRC diagnosed between 6 months and 10 years after colonoscopy. Endoscopists' ADR was categorized into 5 groups (20% to 39.9%, 40% to 44.9%, 45% to 49.9%, 50% to 54.9%, and 55% to 70%). To examine the association of ADR with PCCRC incidence risk, Cox regression models were fitted to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

Of the 110 109 initial colonoscopies, 49 626 colonoscopies done by 113 endoscopists between 2012 and 2017 were included. After 328 778 person-years follow-up, 277 cases of PCCRC were diagnosed. Mean ADR was 48.3% (range, 23% and 70%). Incidence rates of PCCRC from lowest to highest ADR group were 13.13, 10.61, 7.60, 6.01, and 5.78 per 10 000 person-years. There was a significant inverse association between ADR and PCCRC incidence risk, with a 2.35-fold risk increase (95% CI, 1.63 to 3.38) in the lowest group compared with the highest. The adjusted HR for PCCRC associated with 1% increase in ADR was 0.96 (CI, 0.95 to 0.98).

LIMITATION

Adenoma detection rate is partly determined by FIT positivity cutoff; exact values may vary in different settings.

CONCLUSION

In a FIT-based screening program, ADR is inversely associated with PCCRC incidence risk, mandating appropriate colonoscopy quality monitoring in this setting. Increasing endoscopists' ADR may significantly reduce PCCRC risk.

PRIMARY FUNDING SOURCE

None.

Post-endoscopy colorectal cancer after colectomy in inflammatory bowel disease patients: a population-based register study

OBJECTIVES

Long-standing inflammatory bowel disease (IBD) colitis is an indication for endoscopic surveillance. Postcolonoscopy colorectal cancer (PCCRC), cancer detected after a negative colonoscopy, is a quality indicator for colonoscopy. In analogy with PCCRC, we aimed to assess postendoscopy CRC (PECRC) in individuals with IBD who had undergone colectomy.

METHODS

This register study included Swedish adults with an IBD diagnosis who had undergone colectomy and later were examined by either colonoscopy or sigmoidoscopy during 2001-2012. The final study population had a CRC diagnosis within 36 months of the index examination. Poisson regression was used to assess the relative risks (RR) of PECRC.

RESULTS

A total of 33 individuals, 12 with an ileorectal anastomosis and 21 with a rectal remnant, had a CRC diagnosis within 36 months of the index endoscopy. Eleven cancers were detected as CRCs, and 22 (67%) were PECRCs. Compared with individuals aged >70 years, individuals aged <30 years had an RR of 3.1 (P = 0.054) and individuals aged 30-50 years had a RR of 2.6 (P = 0.030). A longer interval between colectomy and index endoscopy (>10 vs. <10 years) was associated with a lower risk of PCCRC (RR = 0.5; P = 0.007). There was no significant difference between the risk for Crohn's disease vs. ulcerative colitis, or between ileorectal anastomosis and rectal remnant risks.

CONCLUSIONS

Continuous surveillance of IBD patients after colectomy is important. In the postcolectomy context, PECRC may be used as a quality indicator.

Detection rates of colorectal neoplasia during colonoscopies and their associated factors in the SCREESCO study

BACKGROUND AND AIM

Colonoscopy quality, including lesion detectability, is variable, and factors influencing lesion detection are not fully understood. This study investigated lesion detection rates during colonoscopies and the associated factors in the SCREEning of Swedish COlons (SCREESCO) study.

METHODS

In this cross-sectional analysis of data from SCREESCO, a large-scale randomized controlled trial of colorectal cancer screening in the Swedish population aged 60 years, we assessed data of first-time colonoscopies performed in both colonoscopy and fecal immunochemical test (FIT) arms.

RESULTS

This study included 16 552 individuals. The adenoma detection rate was 23.9% and 37.8% in colonoscopy and FIT arms, respectively. Regarding colonoscopy procedures, a withdrawal time ≥ 6 min was associated with higher detection rates of advanced adenomas (adjusted odds ratio [AOR] 2.474, 95% confidence interval [CI] 1.295-4.723), adenomas (2.181, 1.515-3.140), and proximal serrated lesions (pSLs) (1.713, 1.007-2.915). Antispasmodic use was associated with higher detection rates of these lesions and sessile serrated lesions (SSLs) (AOR, 95% CI: 1.523, 1.295-1.791; 1.361, 1.217-1.522; 1.450, 1.247-1.687; and 1.810, 1.512-2.167, respectively). Insertion time > 20 min was related to lower detection rates of adenomas, pSLs, and SSLs (AOR, 95% CI: 0.753, 0.639-0.887; 0.640, 0.495-0.828; and 0.704, 0.518-0.955, respectively). The relationship between a recent period and higher detection rates of pSLs and SSLs was also demonstrated.

CONCLUSION

Lesion detectability in SCREESCO was mostly acceptable with room for improvement. In addition to sufficient withdrawal time, antispasmodic use and acquiring skills enabling short insertion time may improve lesion detection.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT02078804.

Colorectal cancer in elderly-onset inflammatory bowel disease: a 1969-2017 Scandinavian register-based cohort study

BACKGROUND

Previous research indicates that the increased relative risk of colorectal cancer (CRC) in inflammatory bowel disease (IBD) is limited to young-onset IBD.

AIM

To estimate risks of incident CRC and death from CRC in elderly-onset IBD METHODS: Patients diagnosed with IBD at age ≥ 60 years between 1969 and 2017 were identified using Danish and Swedish National Patient Registers and histopathology data. We linked data to Cancer and Causes of Death Registers and used Cox regression to estimate hazard ratios (HRs) for CRC diagnosis and death compared to matched (by sex, age, and region) IBD-free individuals.

RESULTS

Among 7869 patients with Crohn's disease followed for 54,220 person-years, and 21,224 patients with ulcerative colitis (UC) followed for 142,635 person-years, 2.10% and 1.90% were diagnosed with CRC, compared to 2.26% and 2.34% of reference individuals (median follow-up 6 and 7 years). The incidence of CRC was elevated during the first year after IBD diagnosis: 4.36 (95% CI = 3.33-5.71) in Crohn's disease and 2.48 (95% CI = 2.03-3.02) in UC, but decreased after the first year of follow-up: 0.69 (95% CI = 0.56-0.86) and 0.78 (95% CI = 0.69-0.88). Once diagnosed with CRC, the risk of CRC death was similar for IBD patients and the general population.

CONCLUSION

The excess risk of CRC in elderly-onset IBD was probably due to bias and not observed beyond the first year. From 2010, the HR for CRC diagnosis more than 1 year after initial IBD diagnosis was lower than in the largely unscreened reference population, supporting the benefit of endoscopic screening and surveillance in patients with IBD.

Characteristics and Survival of Patients With Inflammatory Bowel Disease and Postcolonoscopy Colorectal Cancers

BACKGROUND & AIMS

Postcolonoscopy colorectal cancers (PCCRCs) account for up to 50% of colorectal cancers (CRCs) in patients with inflammatory bowel disease (IBD). We investigated characteristics of IBD patients with PCCRC and their survival.

METHODS

We identified IBD patients (ulcerative colitis [UC] and Crohn's disease) diagnosed with CRC from 1995 to 2015. We defined PCCRC as diagnosed between 6 and 36 months, and detected CRC (dCRC) as diagnosed within 6 months after colonoscopy. We computed prevalence ratios comparing PCCRC vs dCRC and followed up patients from the diagnosis of PCCRC/dCRC until death, emigration, or study end. Mortality was compared using Cox proportional hazards regression models adjusted for sex, age, year of CRC diagnosis, and stage. The main analyses focused on patients with UC.

RESULTS

Among 23,738 UC patients undergoing colonoscopy, we identified 352 patients with CRC, of whom 103 (29%) had PCCRC. Compared with dCRC, PCCRC was associated with a higher prevalence of metastatic cancer (33% vs 20%; prevalence ratio, 1.64; 95% CI, 1.13-2.38), cancers showing mismatch repair deficiency (79% vs 56%; prevalence ratio, 1.40; 95% CI, 1.13-1.72), and proximally located cancers (54% vs 40%; prevalence ratio, 1.34; 95% CI, 1.06-1.69). The 1- and 5-year adjusted hazard ratios of death for PCCRC vs dCRC among UC patients were 1.29 (95% CI, 0.77-2.18) and 1.24 (95% CI, 0.86-1.79), respectively.

CONCLUSIONS

The characteristics of UC-related PCCRC suggest tumor biology as an important factor in the progression to cancer. However, the prognosis of PCCRC appears similar to that of dCRC.

Weakly Supervised Polyp Segmentation in Colonoscopy Images Using Deep Neural Networks

Colorectal cancer (CRC) is a leading cause of mortality worldwide, and preventive screening modalities such as colonoscopy have been shown to noticeably decrease CRC incidence and mortality. Improving colonoscopy quality remains a challenging task due to limiting factors including the training levels of colonoscopists and the variability in polyp sizes, morphologies, and locations. Deep learning methods have led to state-of-the-art systems for the identification of polyps in colonoscopy videos. In this study, we show that deep learning can also be applied to the segmentation of polyps in real time, and the underlying models can be trained using mostly weakly labeled data, in the form of bounding box annotations that do not contain precise contour information. A novel dataset, Polyp-Box-Seg of 4070 colonoscopy images with polyps from over 2000 patients, is collected, and a subset of 1300 images is manually annotated with segmentation masks. A series of models is trained to evaluate various strategies that utilize bounding box annotations for segmentation tasks. A model trained on the 1300 polyp images with segmentation masks achieves a dice coefficient of 81.52%, which improves significantly to 85.53% when using a weakly supervised strategy leveraging bounding box images. The Polyp-Box-Seg dataset, together with a real-time video demonstration of the segmentation system, are publicly available.

Validation of post-colonoscopy colorectal cancer (PCCRC) cases reported at national level following local root cause analysis: REFLECT study

OBJECTIVE

Our aim was to determine aetiology of post-colonoscopy colorectal cancers (PCCRCs) identified from population-based data through local root cause analysis at a high-volume mixed secondary and tertiary referral centre.

DESIGN/METHOD

A subset of national cancer registration data, collected by the National Cancer Registration and Analysis Service, was used to determine PCCRCs diagnosed between 2005 and 2013 at our centre.Root cause analysis was performed for each identified PCCRC, using World Endoscopy Organisation recommendations, to validate it and assess most plausible explanation. We also assessed whether patient, clinician and/or service factors were primarily responsible.

RESULTS

Of 107 'PCCRC' cases provided from the national dataset, 20 were excluded (16 missing data, 4 duplicates). 87 'PCCRC' cases were included of which 58 were true PCCRCs and 29 false PCCRCs.False PCCRCs comprised 17 detected cancers (cancer diagnosed within 6 months of negative colonoscopy) and 12 cases did not meet PCCRC criteria. Inflammatory bowel disease was the most common risk factor (18/58) and the most common site was rectum (19/58). The most common explanation was 'possible missed lesion, prior examination negative but inadequate' (23/58) and clinician factors were primarily responsible for PCCRC occurrence in most cases (37/58).

CONCLUSION

Our single-centre study shows, after local analysis, there was misclassification of PCCRCs identified from a population-based registry. The degree of such error will vary between registries. Most PCCRCs occurred in cases of sub-optimal examination as indicated by poor photodocumentation. Effective mechanisms to feedback root cause analyses are critical for quality improvement.

Risk of a post-colonoscopy colorectal cancer in patients with type 2 diabetes: a Danish population-based cohort study

Objective

Prevalent type 2 diabetes (T2D) is associated with an increased risk of colorectal cancer and could impair the quality of bowel preparation for colonoscopy. This may in turn increase the risk of overlooked precancerous polyps and subsequent risk of post-colonoscopy colorectal cancer (PCCRC). We investigated whether patients with T2D are at increased risk of PCCRC compared with patients without T2D.

Design

We conducted a population-based cohort study of patients with T2D and without T2D undergoing colonoscopy in Denmark (1995–2015). We investigated the risk of PCCRC by calculating >6 to 36 months cumulative incidence proportions (CIPs) treating death and colectomy as competing risks. Using Cox proportional-hazards regression analyses, we also computed HRs of PCCRC, comparing patients with T2D and non-T2D. According to the World Endoscopy Organization guidelines, we calculated PCCRC 3-year rates to estimate the proportions of T2D and non-T2D CRC patients experiencing PCCRC.

Results

We identified 29 031 patients with T2D and 333 232 patients without T2D undergoing colonoscopy. We observed 250 PCCRCs among patients with T2D and 1658 PCCRCs among patients without T2D. The >6 to 36 months CIP after a first-time colonoscopy was 0.64% (95% CI 0.55% to 0.74%) for T2D and 0.36% (95% CI 0.34% to 0.38%) for patients without T2D. The HRs of PCCRC were 1.43 (95% CI 1.21 to 1.72) after a first-time colonoscopy and 1.18 (95% CI 0.75 to 1.85) after a second-time colonoscopy. The PCCRC 3-year rate was 7.9% for patients with T2D and 7.4% for patients without T2D.

Conclusion

T2D may be associated with an increased HR of PCCRC.

Systematic review with meta-analysis: the prevalence of post-colonoscopy colorectal cancers using the World Endoscopy Organization nomenclature

INTRODUCTION

Post-colonoscopy colorectal cancers (PCCRCs) have been proposed as a performance metric for colonoscopy quality assurance programs. Previously, there was no standardised terminology or reporting methods. In 2018, the World Endoscopy Organization (WEO) advised standardised definitions and prevalence calculation methodology.

AIMS

To assess PCCRC burden using WEO standardised methods, to explore causes of heterogeneity, and to review changes in prevalence over time METHODS: We updated a prior systematic review by searching Ovid MEDLINE and EMBASE databases from 1 January 2013 to 31 January 2021 to identify population-based studies (or multicentre studies representative of the local population) reporting PCCRC prevalence (PROSPERO [CRD42020183796]). Two authors independently determined study eligibility, assessed quality, and extracted data. We estimated the PCCRC 3-year prevalence using WEO-recommended methodologies and investigated between-study sources of heterogeneity. We examined changes in prevalence over time.

RESULTS

Fifteen studies reporting on 25 872 PCCRC cases met eligibility criteria. Pooled PCCRC 3 year prevalence was 8.2% (95% CI = 6.9%-9.4%, I²  = 98.2%) across four European studies using WEO precise methodology. Proximal PCCRC prevalence was greater than distal (9.7% [95% CI = 7.0%-12.4%] vs 5.4% [95% CI = 2.9%-7.8%], I²  = 99.2%). Seven studies reporting PCCRC rates over time showed no consistent trend: four showed a decrease, one an increase and two were unchanged. Between-study heterogeneity was high.

CONCLUSIONS

Pooled 3-year PCCRC prevalence was 8.2% (95% CI = 6.9%-9.4%). Despite WEO standardised methodology to define and calculate PCCRC rates, there was significant heterogeneity among studies. Comparing rates between populations remains challenging and additional studies are needed to better understand the global PCCRC burden to inform quality assurance programs.

Risk of a post-colonoscopy colorectal cancer diagnosis in patients with inflammatory bowel disease: a population-based cohort study

BACKGROUND : Post-colonoscopy colorectal cancers (PCCRCs) may account for up to 50 % of all colorectal cancers (CRCs) diagnosed in patients with inflammatory bowel disease (IBD). This may reflect a high colonoscopy frequency; however, evidence remains limited. METHODS : We conducted a cohort study of IBD and non-IBD patients undergoing colonoscopy. We calculated cumulative incidence proportions (CIPs) of PCCRC at 7-36 months after first-time and subsequent colonoscopies. We also computed crude and adjusted hazard ratios (HRs) of PCCRC, comparing IBD with non-IBD patients undergoing first-time and subsequent colonoscopies. Separate analyses were conducted for consecutive colonoscopies. We calculated 3-year rates of PCCRC to estimate the proportion of IBD and non-IBD CRC patients experiencing PCCRC. RESULTS : We observed 138 and 1909 PCCRCs among 34 688 IBD and 358 217 non-IBD patients who underwent colonoscopy. The CIP of PCCRC after first-time colonoscopy was 0.21 % (95 % confidence interval [CI] 0.17 %-0.27 %) for IBD patients and 0.37 % (95 %CI 0.35 %-0.39 %) for non-IBD patients. The adjusted HR of PCCRC after a first-time colonoscopy was 0.96 (95 %CI 0.75-1.22) and the adjusted HRs after subsequent colonoscopies had point estimates around 1.0. The 3-year PCCRC rate was 24.3 % (95 %CI 20.4 %-28.7 %) for IBD and 7.5 % (95 %CI 7.2 %-7.8 %) for non-IBD patients. CONCLUSIONS : Although PCCRCs accounted for a substantial proportion of all IBD-related CRCs, IBD patients had a low CIP of PCCRC. The elevated 3-year PCCRC rates may, among other factors, stem from the increased colonoscopy frequency in IBD patients.