Nonpolypoid colorectal neoplasms: gender differences in prevalence and malignant potential

Colon Capsule Endoscopy in the Diagnosis of Colon Polyps: Who Needs a Colonoscopy?

Colon screening programs have reduced colon cancer mortality. Population screening should be minimally invasive, safe, acceptably sensitive, cost-effective, and scalable. The range of screening modalities include guaiac or immunochemical fecal occult blood testing and CT colonography and colonoscopy. A number of carefully controlled studies concur that second-generation capsule endoscopy has excellent sensitivity for polyp detection and a high negative predictive value. Colon capsules fulfill the screening expectation of safety, high sensitivity for polyp detection, and patient acceptance, and appear to straddle the divide between occult blood testing and colonoscopy. While meeting these criteria, there remains the challenges of scaling, capsule practitioner training, resource allocation, and implementing change of practice. Like CT colonography, capsule screening presents the clinician with a decision on the threshold for colonoscopy referral. Overall, colon capsules are an invaluable tool in polyp detection and colon screening and offer a filter that determines “who needs a colonoscopy?”.

Metachronous neoplasms in patients with laterally spreading tumours during surveillance

Background

Laterally spreading tumours represent a major challenge for endoscopic detection and resection.

Objective

To examine synchronous and metachronous neoplasms in patients with laterally spreading tumours.

Methods

We prospectively collected colonoscopy and histopathology data from patients who underwent colonoscopy in our centre at up to 6 years' follow‐up. Post‐resection surveillance outcomes between laterally spreading tumours, flat colorectal neoplasms 10 mm or greater, and large polypoid colorectal neoplasms, polypoid colorectal neoplasms 10 mm or greater, were compared.

Results

Between 2008 and 2012, 8120 patients underwent colonoscopy for symptoms (84.6%), screening (6.7%) or surveillance (8.7%). At baseline, 151 patients had adenomatous laterally spreading tumours and 566 patients had adenomatous large polypoid colorectal neoplasms. Laterally spreading tumour patients had more synchronous colorectal neoplasms than large polypoid colorectal neoplasm patients (mean 3.34 vs. 2.34, p < 0.001). Laterally spreading tumour patients significantly more often developed metachronous colorectal neoplasms (71.6% vs. 54.2%, p = 0.0498) and colorectal neoplasms with high grade dysplasia/submucosal invasion than large polypoid colorectal neoplasm patients (36.4% vs. 15.8%, p < 0.001). After correction for age and gender, laterally spreading tumour patients were more likely than large polypoid colorectal neoplasm patients to develop a colorectal neoplasm with high grade dysplasia or submucosal invasion (hazard ratio 2.9, 95% confidence interval 1.8–4.6). The risk of metachronous colorectal cancer was not significantly different in laterally spreading tumours compared to large polypoid colorectal neoplasm patients.

Conclusion

Patients with laterally spreading tumours developed more metachronous colorectal neoplasms with high grade dysplasia/submucosal invasion than large polypoid colorectal neoplasm patients. Based on these findings endoscopic treatment and surveillance recommendations for patients with laterally spreading tumours should be optimised.

Summarize the established knowledge on this subject

Laterally spreading tumours (LSTs) are a heterogeneous group of large, predominantly benign flat neoplasms that can be endoscopically treated, requiring additional time and expertise

LSTs consist of different endoscopic subtypes which are predictive of the risk of submucosal invasion (SMI)

Patients with LSTs harbour more synchronous neoplasms than patients with large polypoid colorectal neoplasms (LP‐CRNs)

What are the significant and/or new findings of this study?

Patients with LSTs more frequently have metachronous neoplasms than patients with LP‐CRNs, justifying strict surveillance

LSTs can be effectively managed by conventional endoscopic resections in most cases

IS SUPERFICIAL COLORECTAL LESIONS WITH LOW AND HIGH GRADES INTRAEPITHELIAL NEOPLASMS MORE PREVALENT IN OLDER ABOVE 65 YEARS?

BACKGROUND

Colorectal cancer has a higher incidence in the rectum and sigmoid. However, with the expansion of the diagnosis of superficial lesions interest in the diagnosis and in the role they play in colorectal carcinogenesis has increased.

AIM

To verify the behavior of superficial lesions of the colon and rectum, comparing the pathological and endoscopic findings, below and above 65 years.

METHODS

Cross-sectional study with prospective evaluation of standard protocol, where 200 patients with colorectal superficial lesions were evaluated; they were submitted to colonoscopy and mucosectomy of these lesions. They were divided in two age groups, below and above 65 years.

RESULTS

One hundred-and-eight were women (54%) and 92 men (46%). Most colon lesions were localized in the right colon (95%) and the remaining (5%) in the rectum. In endoscopy, 77.20% were granular lesions in patients under 65 years and 77.90% above. Colon histology showed low grade intraepithelial neoplasia, being 69.79% in patients under and 73.70% in above 65 years. In rectum, above 65 years the incidence of high-grade intraepithelial neoplasia was higher (66.70%).

CONCLUSION

The superficial colorectal lesions have been more endoscopically diagnosed today, and the highest incidence is the granular type, both in the colon and rectum, regardless of age. Regardless the age, histologically colon lesions were more as low grade intraepithelial neoplasia. In rectum, there was distinction for both age groups, being more frequent high grade intraepithelial neoplasia in patients over 65 years.

Risk factors associated with the detection and missed diagnosis of colorectal flat adenoma: a Chinese multicenter observational study

OBJECTIVES

Flat colorectal adenomas have a high risk of malignancy; however, their detection is often difficult due to their flat morphology. In this retrospective, large-scale study, we investigated the prevalence and characteristics of flat adenomas in a population in China.

METHODS

We analyzed the data collected for 16951 consecutive patients who underwent colonoscopy at four participating hospitals between September 2013 and September 2015. All colonoscopies were performed without magnification.

RESULTS

Among the 1,6951 patients, 2938 (17.3%) had adenoma and 796 (4.7%) had flat adenomas. The detection of flat adenoma showed a weak correlation with the detection of adenoma (r = 0.666). Multivariable logistic regression analysis revealed the following independent factors influencing the detection of flat adenomas: patient-related factors of age, presence of warning symptoms, history of adenomas and bowel preparation as well as endoscopist-related factors of endoscopist's level of proficiency, number of colonoscopy operators and withdrawal time.

CONCLUSIONS

The prevalence of flat adenomas in our study on Chinese patients was consistent with that reported from other countries. Factors conducive to the detection of flat adenomas were patient age of > 60 years, warning symptoms, history of adenoma, good bowel preparation, experienced endoscopist, single-operator colonoscopy and colonoscopy withdrawal time of >6 min.

Incidence and distribution of advanced colorectal adenomas in patients undergoing colonoscopy for screening, surveillance, and symptoms

Purpose

The aim of the study was to determine the frequency and distribution of advanced colorectal adenomas (ACAs) in Chinese population.

Methods

The patients who were referred to receive a colonoscopy were divided into three subgroups of screening, surveillance, and symptomatic, and then they were selected based on their indications. The symptomatic subgroup was further broken down into the alarm and non-alarm categories. The location and morphology of all colorectal lesions were both investigated and recorded.

Results

There were significantly more patients with ACAs in the symptomatic subgroup compared to the screening or surveillance subgroup (11.0% vs 4.1%, P<0.001; 11.0% vs 4.6%, P=0.006). No differences were found in the ACA frequency between the alarm and non-alarm categories (11.7% vs 9.7%, P=0.056). One observation was that in the symptomatic subgroup, distal lesions were more likely to contain ACAs than proximal ones (OR 1.50, 95% CI 1.05–2.15, P=0.024). It was also noted that nonpolypoid lesions had significantly higher amounts of ACAs in the symptomatic subgroup (OR 2.09, 95% CI 1.48–2.94, P<0.001) than the other groups.

Conclusion

The incidence of ACAs was higher in patients undergoing a colonoscopy due to their symptoms, compared to the incidence in those who underwent the procedure for screening or surveillance purposes. Additionally, more attention should be focused on distal and nonpolypoid lesions to improve the detection rate of ACAs.

Interval colorectal cancer: a challenging field in colorectal cancer

Accumulated evidence has shown that colonoscopy may not be a perfect tool in screening and reducing the incidence of the colorectal cancer (CRC), because interval CRC (I-CRC), a specific subgroup of CRCs, has been challenging the traditional detection technology in recent years. I-CRC is accounting for an increasing proportion in CRCs. However, the effective procedures to prevent and supervise I-CRC need to be explored. In this review, we summarized the incidence, causes, risk factors, characteristics and management of I-CRC. It would promote the awareness of the special value in the education and training for the gastroenterologists, which plays an important role in conquering CRC.

Morphological classifications of gastrointestinal lesions

In the era of spreading adoption of gastrointestinal endoscopy screening worldwide, endoscopists encounter an increasing number of complex lesions in the gastrointestinal tract. For decision-making on optimal treatment, precise lesion characterization is crucial. Especially the assessment of potential submucosal invasion is of utmost importance as this determines whether endoscopic removal is an option and which technique should be used. To describe a lesion and stratify for the risk of submucosal invasion, several morphological classification systems have been developed. In this manuscript, we thoroughly discuss a systematic approach for the endoscopic assessment of a lesion, which include location, size, Paris classification, lateral spreading tumor classification if applicable and evaluation of the surface pattern with advanced endoscopic imaging techniques. The use of advanced imaging techniques improves the characterization of mucosal surface patterns and helps to determine whether lesions are amenable to endoscopic resection.

Patients With Nonpolypoid (Flat and Depressed) Colorectal Neoplasms at Increased Risk for Advanced Neoplasias, Compared With Patients With Polypoid Neoplasms

BACKGROUND & AIMS

Nonpolypoid colorectal neoplasms (NP-CRNs) are more likely to contain high-grade dysplasia or early-stage cancer than polypoid neoplasms. We aimed to determine the long-term outcomes of patients with at least 1 NP-CRN.

METHODS

We performed a longitudinal cohort study of 4454 patients at a Veterans' Affairs hospital who underwent colonoscopy from 2000 through 2005; 341 were found to have 1 or more NP-CRNs and were matched (3:1) with patients found to have 1 or more polypoid neoplasms (controls, n = 1025). We collected and analyzed data on baseline colonoscopy findings and first follow-up colonoscopy results through August 2014. We calculated the incidence of advanced neoplasia at first follow-up colonoscopy, as defined by the presence of ≥1 tubular or sessile serrated adenomas ≥10 mm in diameter, tubulovillous adenoma, high-grade dysplasia, or invasive cancer.

RESULTS

A significantly higher proportion of patients with 1 or more NP-CRNs (16.0%) were found to have advanced neoplasia at their first follow-up colonoscopy than controls (8.6%); the adjusted risk ratio was 1.6 (95% confidence interval, 1.05-2.6; P = .03). A significantly higher proportion of patients with 1 or more NP-CRNs were found to have additional NP-CRNs at the follow-up colonoscopy (17%) than controls (7%; relative risk, 2.3; 95% confidence interval, 1.5-3.5; P < .001). Similar proportions of patients in each group developed cancers after colonoscopy.

CONCLUSIONS

In a longitudinal cohort study, we found that patients with NP-CRN were more likely to develop additional NP-CRNs and to have advanced neoplasms at their first follow-up colonoscopy than patients with only polypoid neoplasms. However, patients with NP-CRN were not more likely to develop cancers after colonoscopy when surveillance guidelines were followed. Larger studies are needed to determine risk of colorectal cancer in patients with NP-CRN.

Prevalence and Anatomic Distribution of Serrated and Adenomatous Lesions in Patients with Inflammatory Bowel Disease

Background. Sessile serrated adenomas/polyps (SSA/Ps) and traditional serrated adenomas (TSAs) have not been well characterized in patients with inflammatory bowel disease (IBD). This study assesses the prevalence and anatomic distribution of SSA/Ps, TSAs, and conventional adenomas/dysplasia (Ad/Ds) in IBD patients. Methods. IBD patients with serrated, adenomatous, or hyperplastic lesions between 2005 and 2009 were identified in the regional tertiary-care hospital database. Clinicopathological information was reviewed and the histology of biopsies was reevaluated. Results. Ninety-six Ad/Ds, 25 SSA/Ps, and 4 TSAs were identified in 83 patients. Compared to Ad/Ds, serrated lesions were more prevalent in females (p = 0.046). The prevalence of Ad/Ds was 4.95%, SSA/Ps was 1.39%, and TSAs was 0.31%. No relationship was identified between lesion type and IBD type. Comparing all IBD patients, the distribution of lesion types was significantly different (p = 0.02) with Ad/Ds more common distally, SSA/Ps more common proximally, and TSAs evenly distributed. Among Crohn's disease (CD) patients, a similar distribution difference was noted (p < 0.001). However, ulcerative colitis (UC) patients had a uniform distribution of lesion types (p = 0.320). Conclusions. IBD patients have a lower prevalence of premalignant lesions compared to the general population, and the anatomic distribution of lesions differed between CD and UC patients. These findings may indicate an interaction between lesion and IBD pathogenesis with potential clinical implications.

Large Colorectal Lesions: Evaluation and Management

In the last years, a distinctive interest has been raised on large polypoid and non-polypoid colorectal tumors, and specially on flat neoplastic lesions ≥20 mm tending to grow laterally, the so called laterally spreading tumors (LST). Real or virtual chromoendoscopy, endoscopic ultrasound or magnetic resonance should be considered for the estimation of submucosal invasion of these neoplasms. Lesions suitable for endoscopic resection are those confined to the mucosa or selected cases with submucosal invasion ≤1000 μm. Polypectomy or endoscopic mucosal resection remain a first-line therapy for large colorectal neoplasms, whereas endoscopic submucosal dissection in high-volume centers or surgery should be considered for large LSTs for which en bloc resection is mandatory.

Prevalence of non-polypoid colorectal neoplasms in southern Brazil

BACKGROUND AND AIM

Several studies suggest that non-polypoid lesions (NPL) show higher aggressiveness than polypoid lesions, particularly depressed lesions. The present study aimed to assess the prevalence of NPL and the presence of advanced histology in a Brazilian population.

METHODS

Two thousand and sixty-seven superficial neoplastic lesions diagnosed in 1135 patients were analyzed. Lesions were classified as polypoid and non-polypoid (flat and depressed) types, and evaluated for site, size, and histology (adenoma with grade of dysplasia, or early cancer).

RESULTS

Prevalence of NPL was 46.5%. NPL predominated in the right colon (62.9%), whereas polypoid lesions were detected mainly in the left colon (53.2%) (P < 0.001). NPL had a 34% higher probability of occurring in the right colon than polypoid lesions (P < 0.001). NPL were smaller than polypoid lesions (P = 0.03). There were 208 lesions >10 mm, of which 40 (19.2%) had advanced histology: 13% (18/138) of polypoid lesions; 27.3% (18/66) of flat lesions; and 100% (4/4) of depressed lesions (P < 0.001). Among 1859 neoplasms ≤10 mm, only 18 (1%) had advanced histology, and 15 of them were depressed lesions (P < 0.001). Advanced histology was more commonly detected in NPL than in polypoid lesions (P = 0.007), with significant difference in size (P < 0.001). NPL showed more advanced histology than polypoid lesions (OR 2.06; P = 0.01), especially depressed lesions (OR 36.35; P < 0.001). Among all neoplasms, the prevalence of depressed lesions was 2.2%.

CONCLUSION

NPL showed high prevalence and higher aggressiveness than polypoid lesions, especially the depressed type.

Malignancy in large colorectal lesions

CONTEXT

The size of colorectal lesions, besides a risk factor for malignancy, is a predictor for deeper invasion objectives: To evaluate the malignancy of colorectal lesions ≥20 mm.

METHODS

Between 2007 and 2011, 76 neoplasms ≥20 mm in 70 patients were analyzed.

RESULTS

The mean age of the patients was 67.4 years, and 41 were women. Mean lesion size was 24.7 mm ± 6.2 mm (range: 20 to 50 mm). Half of the neoplasms were polypoid and the other half were non-polypoid. Forty-two (55.3%) lesions were located in the left colon, and 34 in the right colon. There was a high prevalence of III L (39.5%) and IV (53.9%) pit patterns. There were 72 adenomas and 4 adenocarcinomas. Malignancy was observed in 5.3% of the lesions. Thirty-three lesions presented advanced histology (adenomas with high-grade dysplasia or early adenocarcinoma), with no difference in morphology and site. Only one lesion (1.3%) invaded the submucosa. Lesions larger than 30 mm had advanced histology (P = 0.001). The primary treatment was endoscopic resection, and invasive carcinoma was referred to surgery. Recurrence rate was 10.6%.

CONCLUSIONS

Large colorectal neoplasms showed a low rate of malignancy. Endoscopic treatment is an effective therapy for these lesions.

Trouble in Paris (classification): polyp morphology is in the eye of the beholder

Key challenges to colonoscopy outcomes include polyp detection, appropriate polyp resection, and prediction of recurrent polyps. The Paris classification of gastrointestinal neoplasia has been used to attempt to address these challenges based on the hypothesis that the visual appearance of a polyp (e.g., sessile, flat, depressed) has an impact on these outcomes. Although the Paris classification has been widely used as a measurement tool in research, and reported to predict outcomes such as risk for high-grade dysplasia and invasive carcinoma, interobserver variability associated with this classification scheme has not been studied. In the current issue of the Red Journal, van Doorn et al. studied the interobserver variation of Paris classification in 85 colorectal polyps assessed by seven expert colonoscopists. They found that interobserver variation measured by kappa was only moderate (kappa=0.42; 95% confidence interval: 0.39-0.45). These findings suggest that without methods to improve interobserver variability, the Paris classification cannot routinely be used for research or routine practice. New approaches to characterizing polyp appearance may be required to use morphology as a predictor of clinical outcomes.

Gender- and site-specific differences of colorectal neoplasia relate to vitamin D

BACKGROUND

The effect of vitamin D on colorectal adenomas may vary with regard to gender, localisation and histological type of the lesion.

AIM

To define the role of vitamin D and gender in a Caucasian cohort of subjects undergoing screening colonoscopy after consideration of established risk factors.

METHODS

One thousand five hundred and thirty-two subjects (813 males, 58.8 ± 9.7 years; 719 females, 59.7 ± 10.7 years) were allocated to tertiles of 25-hydroxyvitamin D3 [25(OH)D3 ] serum concentrations. The number, localisation, size and histology of the detected colonic lesions were recorded.

RESULTS

Among men, no association was found between vitamin D and the total number, size and histological stage of adenomas at any site. In female subjects, less women with adenomas were found in the highest vitamin D tertile (N = 42/239; 17.2%) as compared to the low vitamin D group (N = 60/240; 25.0%; P = 0.035). In particular, the number of women with adenomas in the proximal colon was significantly lower in the highest tertile (N = 21/239, 8.8%) compared to the low vitamin D group (N = 41/240; 17.1%; P = 0.007). The rates at other sites were not different. The inverse association of vitamin D serum concentrations with the presence of adenomas in the proximal colon was maintained after adjustment for potential confounders. In 80 women on vitamin D supplementation, the rate of adenomas was lower compared to those not on supplementation (3/80; 3.8%; vs. 90/719; 12.5%; P = 0.016).

CONCLUSIONS

A potential preventive effect of vitamin D on colorectal adenomas was found in the proximal colon in women. This observation is supported by further decrease of lesions in the proximal colon of women on vitamin D supplementation.

Interval colorectal cancers: what and why

An increasing number of studies now indicate that colonoscopic examination is not perfect in preventing colorectal cancer (CRC), especially of the proximal colon. Several factors can be implicated in the occurrence of interval CRCs--further referred to as postcolonoscopy CRCs-, such as missed, incompletely resected lesions and newly developed cancers. Missed lesions represent by far the dominant cause of postcolonoscopy CRCs, with nonpolypoid (flat or depressed) neoplasms and sessile serrated polyps playing a significant role. Molecular events underlying progression of such lesions may further augment the cancer risk. In this article, we review the literature about postcolonoscopy CRC risk and the most common explanations. We discuss potential implications, paying special attention to improvements required in education and training.

Promoter methylation of Wnt-antagonists in polypoid and nonpolypoid colorectal adenomas

BACKGROUND

Nonpolypoid adenomas are a subgroup of colorectal adenomas that have been associated with a more aggressive clinical behaviour compared to their polypoid counterparts. A substantial proportion of nonpolypoid and polypoid adenomas lack APC mutations, APC methylation or chromosomal loss of the APC locus on chromosome 5q, suggesting the involvement of other Wnt-pathway genes. The present study investigated promoter methylation of several Wnt-pathway antagonists in both nonpolypoid and polypoid adenomas.

METHODS

Quantitative methylation-specific PCR (qMSP) was used to evaluate methylation of four Wnt-antagonists, SFRP2, WIF-1, DKK3 and SOX17 in 18 normal colorectal mucosa samples, 9 colorectal cancer cell lines, 18 carcinomas, 44 nonpolypoid and 44 polypoid adenomas. Results were integrated with previously obtained data on APC mutation, methylation and chromosome 5q status from the same samples.

RESULTS

Increased methylation of all genes was found in the majority of cell lines, adenomas and carcinomas compared to normal controls. WIF-1 and DKK3 showed a significantly lower level of methylation in nonpolypoid compared to polypoid adenomas (p < 0.01). Combining both adenoma types, a positive trend between APC mutation and both WIF-1 and DKK3 methylation was observed (p < 0.05).

CONCLUSIONS

Methylation of Wnt-pathway antagonists represents an additional mechanism of constitutive Wnt-pathway activation in colorectal adenomas. Current results further substantiate the existence of partially alternative Wnt-pathway disruption mechanisms in nonpolypoid compared to polypoid adenomas, in line with previous observations.

Optical diagnosis of colorectal polyps using high-definition i-scan: An educational experience

AIM: To examine performances regarding prediction of polyp histology using high-definition (HD) i-scan in a group of endoscopists with varying levels of experience.

METHODS: We used a digital library of HD i-scan still images, comprising twin pictures (surface enhancement and tone enhancement), collected at our university hospital. We defined endoscopic features of adenomatous and non-adenomatous polyps, according to the following parameters: color, surface pattern and vascular pattern. We familiarized the participating endoscopists on optical diagnosis of colorectal polyps using a 20-min didactic training session. All endoscopists were asked to evaluate an image set of 50 colorectal polyps with regard to polyp histology. We classified the diagnoses into high confidence (i.e., cases in which the endoscopist could assign a diagnosis with certainty) and low confidence diagnoses (i.e., cases in which the endoscopist preferred to send the polyp for formal histology). Mean sensitivity, specificity and accuracy per endoscopist/image were computed and differences between groups tested using independent-samples t tests. High vs low confidence diagnoses were compared using the paired-samples t test.

RESULTS: Eleven endoscopists without previous experience on optical diagnosis evaluated a total of 550 images (396 adenomatous, 154 non-adenomatous). Mean sensitivity, specificity and accuracy for diagnosing adenomas were 79.3%, 85.7% and 81.1%, respectively. No significant differences were found between gastroenterologists and trainees regarding performances of optical diagnosis (mean accuracy 78.0% vs 82.9%, P = 0.098). Diminutive lesions were predicted with a lower mean accuracy as compared to non-diminutive lesions (74.2% vs 93.1%, P = 0.008). A total of 446 (81.1%) diagnoses were made with high confidence. High confidence diagnoses corresponded to a significantly higher mean accuracy than low confidence diagnoses (84.0% vs 64.3%, P = 0.008). A total of 319 (58.0%) images were evaluated as having excellent quality. Considering excellent quality images in conjunction with high confidence diagnosis, overall accuracy increased to 92.8%.

CONCLUSION: After a single training session, endoscopists with varying levels of experience can already provide optical diagnosis with an accuracy of 84.0%.

Tracking the molecular features of nonpolypoid colorectal neoplasms: a systematic review and meta-analysis

OBJECTIVES

Nonpolypoid colorectal neoplasms (NP-CRNs) are proposed as a major contributor to the occurrence of interval cancers, but their underlying biology remains controversial. We conducted a systematic review and meta-analysis to clarify the major biological events in NP-CRNs.

METHODS

We systematically searched for studies examining molecular characteristics of NP-CRNs. We performed random effect meta-analyses. We measured the heterogeneity among studies using I(2) and possible publication bias using funnel plots.

RESULTS

Fifty-three studies on KRAS, APC, or BRAF mutations, microsatellite instability (MSI), CpG island methylator phenotype (CIMP), or DNA promoter hypermethylation were included. We observed less KRAS mutations (summary odds ratio (OR) 0.30, confidence interval (CI)=0.19-0.46, I(2)=77.4%, CI=70.1-82.9) and APC mutations (summary OR 0.42, CI=0.24-0.72, I(2)=22.6%, CI=0.0-66.7) in NP-CRNs vs. protruded CRNs, whereas BRAF mutations were more frequent (summary OR 2.20, CI=1.01-4.81, I(2)=0%, CI=0-70.8), albeit all with large heterogeneity. Less KRAS mutations were especially found in NP-CRNs subtypes: depressed CRNs (summary OR 0.12, CI=0.05-0.29, I(2)=0%, CI=0-67.6), non-granular lateral spreading tumors (LSTs-NG) (summary OR 0.61, CI=0.37-1.0, I(2)=0%, CI=0-74.6), and early nonpolypoid carcinomas (summary OR 0.11, CI=0.06-0.19, I(2)=0%, CI=0-58.3). MSI frequency was similar in NP-CRNs and protruded CRNs (summary OR 0.99, CI=0.21-4.71, I(2)=70.3%, CI=38.4-85.7). Data for promoter hypermethylation and CIMP were inconsistent, precluding meaningful conclusions.

CONCLUSIONS

This meta-analysis provides indications that NP-CRNs are molecularly different from protruded CRNs. In particular, some subtypes of NP-CRNs, the depressed and LST-NG, are featured by less KRAS mutations than polypoid CRNs. Prospective, multicenter studies are needed to clarify the molecular pathways underlying nonpolypoid colorectal carcinogenesis and potential implications for surveillance intervals.

Risk factors associated with colorectal flat adenoma detection

OBJECTIVES

Colorectal flat adenomas have been associated with a higher risk of colorectal malignancy. We describe demographic characteristics and endoscopic findings in patients with colorectal flat adenomas.

METHODS

In total, 1934 consecutive patients undergoing colonoscopy were prospectively included. Polyp shape was classified according to the Japanese classification. Chromoendoscopy was applied whenever a flat lesion was suspected. Indications for colonoscopy, demographic data, and characteristics of neoplastic lesions were recorded. Patients were classified as follows: group 1, no adenomas (n=1250); group 2, only protruding adenomas (n=427); group 3, protruding and flat adenomas (n=118); and group 4, only flat adenomas (n=139).

RESULTS

Approximately one in every 10 patients (13.2%) had flat adenomas. Among them, concomitant protruding adenomas were identified in approximately half of the cases. In multivariate analysis, age older than 50 years [odds ratio (OR)=1.62; 95% confidence interval (CI)=1.08-2.43, P=0.02], protruding adenomas (OR=2.17; 95% CI=1.65-2.87, P<0.001), follow-up colonoscopy for polyps or cancer (OR=2.22; 95% CI=1.59-3.10, P<0.001), screening colonoscopy (OR=1.60, 95% CI=1.15-2.22, P=0.005), and specifically trained endoscopist (OR=2.02, 95% CI=1.53-2.68, P<0.001) were associated independently with flat adenoma detection.

CONCLUSION

Flat adenomas have specific demographic factors that might help to improve detection. Particularly, age older than 50 years, colorectal neoplasia surveillance, and the presence of protruding adenomas should alert endoscopists to the possible presence of these lesions. Trained endoscopists may offer a greater chance of detecting these lesions.