Findings on optical colonoscopy after positive CT colonography exam

Magnitude, Risk Factors, and Factors Associated With Adenoma Miss Rate of Tandem Colonoscopy: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

We performed a systematic review and meta-analysis to comprehensively estimate adenoma miss rate (AMR) and advanced AMR (AAMR) and explore associated factors.

METHODS

We searched the PubMed, Web of Science, and Ovid EMBASE databases for studies published through April 2018 on tandem colonoscopies, with AMR and AAMR as the primary outcomes. We performed meta-regression analyses to identify risk factors and factors associated with outcome. Primary outcomes were AMR and AAMR and secondary outcomes were AMR and AAMR for different locations, sizes, pathologies, morphologies, and populations.

RESULTS

In a meta-analysis of 43 publications and more than 15,000 tandem colonoscopies, we calculated miss rates of 26% for adenomas (95% confidence interval [CI] 23%-30%), 9% for advanced adenomas (95% CI 4%-16%), and 27% for serrated polyps (95% CI 16%-40%). Miss rates were high for proximal advanced adenomas (14%; 95% CI 5%-26%), serrated polyps (27%; 95% CI 16%-40%), flat adenomas (34%; 95% CI 24%-45%), and in patients at high risk for colorectal cancer (33%; 95% CI 26%-41%). Miss rates could be decreased by adequate bowel preparation and auxiliary techniques (P = .06; P = .04, and P = .01, respectively). The adenoma detection rate (ADR), adenomas per index colonoscopy, and adenomas per positive index colonoscopy (APPC) were independently associated with AMR (P = .02, P = .01, and P = .008, respectively), whereas APPC was the only factor independently associated with AAMR (P = .006). An APPC value greater than 1.8 was more effective in monitoring AMR (31% vs 15% for AMR P < .0001) than an ADR value of at least 34% (27% vs 17% for AMR; P = .008). The AAMR of colonoscopies with an APPC value below 1.7 was 35%, vs 2% for colonoscopies with an APPC value of at least 1.7 (P = .0005).

CONCLUSIONS

In a systematic review and meta-analysis, we found that adenomas and advanced adenomas are missed (based on AMR and AAMR) more frequently than previously believed. In addition to ADR, APPC deserves consideration as a complementary indicator of colonoscopy quality, if it is validated in additional studies.

Imaging Matrix Metalloproteases in Spontaneous Colon Tumors: Validation by Correlation with Histopathology

The use of fluorescent probes in conjunction with white-light colonoscopy is a promising strategy for improving the detection of precancerous colorectal lesions, in particular flat (sessile) lesions that do not protrude into the lumen of the colon. We describe a method for determining the sensitivity and specificity of an enzymatically activated near-infrared probe (MMPSense680) for the detection of colon lesions in a mouse model (APC^+/Min-FCCC) of spontaneous colorectal cancer. Fluorescence intensity correlates directly with the activity of matrix metalloproteinases (MMPs). Overexpression of MMPs is an early event in the development of colorectal lesions. Although the probe employed serves as a reporter of the activity of MMPs, our method can be applied to any fluorescent probe that targets an early molecular event in the development of colorectal tumors.

Carpet lesions detected at CT colonography: clinical, imaging, and pathologic features

PURPOSE

To describe carpet lesions (laterally spreading tumors ≥ 3 cm) detected at computed tomographic (CT) colonography, including their clinical, imaging, and pathologic features.

MATERIALS AND METHODS

The imaging reports for 9152 consecutive adults undergoing initial CT colonography at a tertiary center were reviewed in this HIPAA-compliant, institutional review board-approved retrospective study to identify all potential carpet lesions detected at CT colonography. Carpet lesions were defined as morphologically flat, laterally spreading tumors 3 cm or larger. For those patients with neoplastic carpet lesions, CT colonography studies were analyzed to determine maximal lesion width and height, oral contrast material coating, segmental location, and computer-aided detection (CAD) findings. Demographic data and details of clinical treatment in these patients were reviewed.

RESULTS

Eighteen carpet lesions in 18 patients (0.2%; mean age, 67.1 years; eight men, 10 women) were identified and were subsequently confirmed at colonoscopy and pathologic examination among 20 potential flat masses (≥3 cm) prospectively identified at CT colonography (there were two nonneoplastic rectal false-positive findings). No additional neoplastic carpet lesions were found in the cohort undergoing colonoscopy after CT colonography and/or surgery (there were no false-negatives). Mean lesion width was 46.5 mm (range, 30-80 mm); mean lesion height was 7.9 mm (range, 4-14 mm). Surface retention of oral contrast material was noted in all 18 cases. All but two lesions were located in the distal rectosigmoid or proximal right colon. At CAD, 17 (94.4%) lesions were detected (mean, 6.2 CAD marks per lesion). Sixteen lesions (88.9%) demonstrated advanced histologic features, including a villous component (n = 11), high-grade dysplasia (n = 4), and invasive cancer (n = 5). Sixteen patients (88.9%) required surgical treatment for complete excision.

CONCLUSION

CT colonography can effectively depict carpet lesions. Common features in this series included older patient age, rectal or cecal location, surface coating with oral contrast material, multiple CAD hits, advanced yet typically benign histologic features, and surgical treatment.

Missed lesions at CT colonography: lessons learned

Misinterpretation at CT colonography (CTC) can result in either a colorectal lesion being missed (false-negative) or a false-positive diagnosis. This review will largely focus on potential missed lesions-and ways to avoid such misses. The general causes of false-negative interpretation at CTC can be broadly characterized and grouped into discrete categories related to suboptimal study technique, specific lesion characteristics, anatomic location, and imaging artifacts. Overlapping causes further increase the likelihood of missing a clinically relevant lesion. In the end, if the technical factors of bowel preparation, colonic distention, and robust CTC software are adequately addressed on a consistent basis, and the reader is aware of all the potential pitfalls at CTC, important lesions will seldom be missed.

The new view of colon cancer screening: forwards and backwards

Many different techniques for colon cancer screening are available. The fecal immunochemical test is best for fecal-based screening, although the DNA investigation may be more specific when further developed. Computed tomographic colonography is as good as colonoscopy for detecting colon cancer and is almost as good as colonoscopy for detecting advanced adenomas, but has limitations. The flexible sigmoidoscopic examination markedly decreases the incidence of cancer in the visualized segments, but colonoscopy is currently the best procedure for evaluating the large bowel. Techniques for retroflexion or backward view of the colon have been investigated, with all showing increased polyp detection.

CT colonography: pitfalls in interpretation

As with any radiologic imaging test, there are several potential interpretive pitfalls at CT colonography that need to be recognized and handled appropriately. Perhaps the single most important step in learning to avoid most of these diagnostic traps is simply to be aware of their existence. With a little experience, most of these potential pitfalls are easily recognized. This article systematically covers the key pitfalls confronting the radiologist at CT colonography interpretation, primarily dividing them into those related to technique and those related to underlying anatomy. Tips and pointers for how to effectively handle these potential pitfalls are included.

Detection of colorectal adenomas using a bioactivatable probe specific for matrix metalloproteinase activity

A significant proportion of colorectal adenomas, in particular those that lack an elevated growth component, continue to escape detection during endoscopic surveillance. Elevation of the activity of matrix metalloproteinases (MMPs), a large family of zinc endopeptidases, in adenomas serves as a biomarker of early tumorigenesis. The goal of this study was to assess the feasibility of using a newly developed near-infrared bioactivatable probe (MMPSense 680) that reports the activity of a broad array of MMP isoforms to detect early colorectal adenomas. Adenomatous polyposis coli (Apc)(+/Min-FCCC) mice that spontaneously develop multiple colorectal adenomas were injected with MMPSense 680, and the colons were imaged in an IVIS Spectrum system ex vivo. Image analyses were correlated with histopathologic findings for all regions of interest (ROIs). The biochemical basis of fluorescent signal was investigated by immunohistochemical staining of MMP-7 and -9. A strong correlation (Kendall = 0.80) was observed between a positive signal and the presence of pathologically confirmed colonic adenomas; 92.9% of the 350 ROIs evaluated were classified correctly. The correlation between two independent observers was 0.87. MMP-7 expression was localized to epithelial cells of adenomas and microadenomas, whereas staining of MMP-9 was found in infiltrating polymorphonuclear leukocytes within the adenomas. MMPSense 680 identifies colorectal adenomas, both polypoid and nonpolypoid, in Apc(+/Min-FCCC) mice with high specificity. Use of this fluorescent probe in combination with colonoscopy could aid in preventing colorectal neoplasias by providing new opportunities for early detection and therapeutic intervention.

Low rates of cancer or high-grade dysplasia in colorectal polyps collected from computed tomography colonography screening

BACKGROUND & AIMS

In patients with polyps detected at computed tomography colonography (CTC) screening, management decisions are influenced by the likelihood of important polyp histology. We assess the rates of cancer and high-grade dysplasia among patients found to have small (6-9 mm) and large (>or=10 mm) colorectal polyps at CTC.

METHODS

We reviewed results from 5124 consecutive adults (mean age, 56.9 y; 2792 women) who received CTC screening at 1 institution over a 52-month period. All nondiminutive lesions confirmed at subsequent colonoscopy were grouped by size and histology features. Rates of cancer and high-grade dysplasia were calculated for various sizes. Adenomas were classified as advanced if they were 10 mm or greater and/or contained high-grade dysplasia or a prominent villous component.

RESULTS

A total of 755 polyps 6 mm or greater were identified during colonoscopy examinations in 479 patients. The rate of malignancy, according to polyp size, was 0% (0 of 464) for polyps 6 to 9 mm, 0.9% (2 of 216) for polyps 10 to 19 mm, 6.1% (2 of 33) for polyps 20 to 29 mm, and 38.1% (16 of 42) for polyps 30 mm or greater. High-grade dysplasia was observed in 0.4% (2 of 464) of 6- to 9-mm polyps and 7.9% (23 of 291) of lesions 10 mm or greater. A prominent villous component was seen in 3.4% (16 of 464) of 6- to 9-mm polyps. The overall rate of advanced histology in small polyps was 3.9% (18 of 464).

CONCLUSIONS

Small (6-9 mm) polyps rarely contained high-grade dysplasia (0.4%); none was malignant. The malignancy rate for large (1-2 cm) colorectal polyps was less than 1%. These findings indicate the potential for less aggressive management of lesions detected by CTC.

Could the colonic capsule PillCam Colon be clinically useful for selecting patients who deserve a complete colonoscopy?: results of clinical comparison with colonoscopy in the perspective of colorectal cancer screening

OBJECTIVES

Preliminary studies have shown the possibility of detecting colonic polyps and tumors using the PillCam Colon capsule endoscope (CCE) (Given Imaging, Yoqneam, Israel). The aim of this study was to evaluate the ability of CCE to detect clinically relevant colonic findings as compared with colonoscopy, and further, to test the assumption that CCE used in the frame of colorectal cancer (CRC) screening could accurately discriminate patients deserving a complete colonoscopy.

METHODS

A total of 128 patients (67 men, 55+/-14 years) with an indication of colonoscopy were investigated by CCE, followed by colonoscopy under general anesthesia on the next day. Bowel cleansing was carried out according to a previously published protocol (3 l polyethylene glycol+2 doses of sodium phosphate solution). All CCE recordings were read by the same physician and all colonoscopies, performed by the same operator, were blinded to each other's results. The primary outcome of the study was the decision made by the CCE reader to indicate a colonoscopy, compared with the final result of the colonoscopy. Secondary outcomes were the agreement between CCE and colonoscopy for making a diagnosis of colorectal disease, as well as detection rate, number, and size of polyps.

RESULTS

Two patients were excluded: one did not swallow the capsule and the other was diagnosed with a jejunal stenosis by the CCE. The CCE found at least one clinically relevant colonic finding in 71 patients (56.3%), and the colonoscopy results confirmed this finding in 56 patients, showing a sensitivity of CCE of 87.5% (confidence interval (CI) 79.4-95.6%) and a specificity of 75.8% (CI 65.4-86.2%). With a prevalence of 50.8% of clinically relevant findings at colonoscopy, the positive predictive value of CCE was 78.9%, and the negative predictive value (NPV) was 85.4%. The agreement between CCE and colonoscopy was significant for the detection of any colonic lesion (P<0.0001), polyps (P<0.001), as well as for the detection of the number (P<0.0001) and size (P=0.0083) of polyps. Tolerance of the procedure was excellent, and no complication was reported.

CONCLUSIONS

In the setting of this study, CCE seemed to be effective in detecting clinically significant colonic findings in patients with an indication of colonoscopy. The high NPV and excellent tolerance of CCE suggest that it could be evaluated in large CRC-screening programs and further studies in screening conditions should also evaluate its cost-efficacy ratio.

Performance of CT colonography for detecting small, diminutive, and flat polyps

The primary goal of colorectal cancer screening and prevention is the detection and removal of advanced neoplasia. Computerized tomography (CT) colonography is now well established as an effective screening test. Areas of greater uncertainty include the performance characteristics of CT colonography for detecting small (6-9 mm), diminutive (< or =5 mm), and flat (nonpolypoid) lesions. However, the actual clinical relevance of small, diminutive, and flat polyps has also been the source of debate. This article addresses these controversial and often misunderstood issues.

Finding polyps at colonoscopy previously noted on CT colonography

Colon screening examinations have been shown to discover neoplastic lesions at an early stage. Even the most careful studies by colonoscopy and by computed tomographic colonography (CTC) can overlook tumors with a diameter greater than 5 mm. Advances in technology have continually improved the ability to find polyps, which will lead to a real decrease in colorectal cancer incidence.

Performance of CT colonography in clinical trials

The amount of data accumulated in trials of CT colonography (CTC) has greatly increased in the past decade. The information from these studies is shaping clinical practice and public health policy regarding screening for colorectal cancer (CRC). This article examines the performance of CTC in clinical trials for individuals at average risk and increased risk for CRC. It also addresses the efficacy of CTC after incomplete colonoscopy, when colon preparations are reduced or eliminated, and in academic versus nonacademic environments. The data suggest that CTC is effective especially for the detection of larger lesions and when more advanced imaging technology is used.

Positive predictive value for polyps detected at screening CT colonography

PURPOSE

To determine the positive predictive value (PPV) for polyps detected at CT colonography (CTC).

METHODS

Assessment of 739 colorectal lesions >or=6 mm detected prospectively at CTC screening in 479 patients was performed. By-polyp PPV was analyzed according to small (6-9 mm) versus large (>or=10 mm) size; morphology (sessile/pedunculated/flat); diagnostic confidence level (3 = most confident, 1 = least confident); and histology. By-patient PPV was analyzed at various polyp size thresholds.

RESULTS

By-polyp PPV for CTC-detected lesions >or=6 mm, 6-9 mm, and >or=10 mm was 91.6% (677/739), 90.1% (410/451), and 92.7% (267/288), respectively (p = 0.4). By-polyp PPV according to sessile, pedunculated, flat, and mass-like morphology was 92.5% (441/477), 96.5% (139/144), 77.7% (73/94), and 97.6% (40/41), respectively (p < 0.0001 for flat versus polypoid morphology). By-polyp PPV according to diagnostic confidence level was 94.7% (554/585) for highest (= level 3), 83.5% (106/127) for intermediate (= level 2), and 63.0% (17/27) for lowest (= level 1) confidence (p < 0.0001 for levels-2/3 versus level-1). By-patient PPV at 6-mm, 8-mm, 10-mm, and 30-mm polyp size thresholds was 92.3% (442/479), 93.0% (306/329), 93.1% (228/245), and 97.4% (38/39), respectively.

CONCLUSION

The overall per-polyp and per-patient PPV for lesions >or=6 mm was 92% for CTC screening. Increased diagnostic confidence and polypoid (non-flat) morphology correlated with a higher PPV, whereas small versus large polyp size had very little effect.

Colorectal cancer screening with CT colonography: key concepts regarding polyp prevalence, size, histology, morphology, and natural history

OBJECTIVE

The purpose of this article is to provide a timely update on a variety of key polyp topics to construct a proper framework for physicians who are interested in providing CT colonography screening as a clinical service.

CONCLUSION

As the medical community considers the expansion of CT colonography for screening, we believe it is prudent to update and review several key concepts regarding colorectal polyps. In particular, it is important to replace the older literature derived from high-risk and symptomatic cohorts with the wealth of newer and more applicable data from average-risk and asymptomatic screening cohorts. Familiarity with current concepts regarding flat (nonpolypoid) lesions and the natural history of small colorectal polyps is also vital to the effective application of this technique.