Colorectal cancer screening with CT colonography: key concepts regarding polyp prevalence, size, histology, morphology, and natural history. AJR Am J Roentgenol. 2009;193:40-46. [PMID: 19542393 DOI: 10.2214/ajr.08.1709]

CT Colonography for Colorectal Cancer Prevention and Detection: Integration Into Clinical Practice, From the AJR Special Series on Screening

CT colonography (CTC) is a CT examination, performed with low dose and typically without IV contrast media, optimized to detect colorectal polyps and cancer. Despite extensive supporting data, CTC has had variable acceptance and use over the past two decades, particularly for a main indication of colorectal cancer screening. CTC is now at an inflection point after the approval in 2025 by CMS for reimbursement of CTC performed for colorectal cancer screening. Widespread use of CTC for CRC screening could help increase screening adherence rates and prevent cancer incidence. Nonetheless, radiologists must incorporate emerging knowledge regarding polyps' natural history and recognition of sessile serrated lesions, to leverage the screening efficiencies of CTC-based screening. The purposes of this article are to describe the current status of CRC in the United States and United Kingdom with consideration of historical reasons that have limited the test's use along with recent events that may portend a marked change in the test's acceptance; to highlight the challenges and potential solutions toward successful widespread CTC implementation; and to present new concepts in CTC and CRC screening relevant to radiologists.

The absolute number of small and diminutive adenomas with high-grade dysplasia is substantially higher compared with large adenomas: a retrospective pooled study

Introduction

The risk that a large polyp (≥10 mm) evolves into high-grade dysplasia (HGD) is relatively high compared with that of a small/diminutive polyp (<10 mm). Recently, the detection of small and diminutive polyps has been substantially improved with the advancement of endoscopy. However, further research is needed on the role of the incidence of HGD caused by the co-occurrence of small and diminutive polyps in the progression of HGD. In this study, we aim to investigate whether and how the small and diminutive polyps correlate with the incidence of HGD in the population.

Methods

The pooled data were deeply analyzed from four published randomized controlled trials (RCTs) regarding colon polyp detection. All polyps detected were examined and confirmed by pathologists. The primary outcome was the composition ratio of the HGD polyps in each polyp size category.

Results

Among a total of 3,179 patients with 2,730 polyps identified, there were 83 HGD polyps confirmed, and 68 patients had at least one polyp with HGD. The risk of development of HGD was lower for a single small and diminutive polyp than for one large polyp (2.18% vs. 22.22%, P < 0.0001). On the contrary, the composition ratio for HGD from small and diminutive polyps was significantly higher than that from the large ones (68.67% vs. 31.33%, P < 0.0001). The combined number of HGD presented a trend negatively correlated to size.

Conclusions

Our data demonstrated that the absolute number of HGD significantly derives more from small and diminutive polyps than from the large ones, and the collective number of small and diminutive polyps per patient is indicative of his/her HGD exposure. These findings positively provide novel perspectives on the management of polyps and may further optimize the prevention of colorectal cancer.

Systematic Review Registration

http://www.chictr.org.cn, identifier ChiCTR1900025235, ChiCTR1800017675, ChiCTR1800018058, and ChiCTR1900023086.

Canadian Association of Radiologists Practice Guidelines for Computed Tomography Colonography

Colon cancer is the third most common malignancy in Canada. Computed tomography colonography (CTC) provides a creditable and validated option for colon screening and assessment of known pathology in patients for whom conventional colonoscopy is contraindicated or where patients self-select to use imaging as their primary modality for initial colonic assessment. This updated guideline aims to provide a toolkit for both experienced imagers (and technologists) and for those considering launching this examination in their practice. There is guidance for reporting, optimal exam preparation, tips for problem solving to attain high quality examinations in challenging scenarios as well as suggestions for ongoing maintenance of competence. We also provide insight into the role of artificial intelligence and the utility of CTC in tumour staging of colorectal cancer. The appendices provide more detailed guidance into bowel preparation and reporting templates as well as useful information on polyp stratification and management strategies. Reading this guideline should equip the reader with the knowledge base to perform colonography but also provide an unbiased overview of its role in colon screening compared with other screening options.

Natural History of Colorectal Polyps Undergoing Longitudinal in Vivo CT Colonography Surveillance

Background The natural history of colorectal polyps is not well characterized due to clinical standards of care and other practical constraints limiting in vivo longitudinal surveillance. Established CT colonography (CTC) clinical screening protocols allow surveillance of small (6-9 mm) polyps. Purpose To assess the natural history of colorectal polyps followed with CTC in a clinical screening program, with histopathologic correlation for resected polyps. Materials and Methods In this retrospective study, CTC was used to longitudinally monitor small colorectal polyps in asymptomatic adult patients from April 1, 2004, to August 31, 2020. All patients underwent at least two CTC examinations. Polyp growth patterns across multiple time points were analyzed, with histopathologic context for resected polyps. Regression analysis was performed to evaluate predictors of advanced histopathology. Results In this study of 475 asymptomatic adult patients (mean age, 56.9 years ± 6.7 [SD]; 263 men), 639 unique polyps (mean initial diameter, 6.3 mm; volume, 50.2 mm3) were followed for a mean of 5.1 years ± 2.9. Of these 639 polyps, 398 (62.3%) underwent resection and histopathologic evaluation, and 41 (6.4%) proved to be histopathologically advanced (adenocarcinoma, high-grade dysplasia, or villous content), including two cancers and 38 tubulovillous adenomas. Advanced polyps showed mean volume growth of +178% per year (752% per year for adenocarcinomas) compared with +33% per year for nonadvanced polyps and -3% per year for unresected, unretrieved, or resolved polyps (P < .001). In addition, 90% of histologically advanced polyps achieved a volume of 100 mm3 and/or volume growth rate of 100% per year, compared with 29% of nonadvanced and 16% of unresected or resolved polyps (P < .001). Polyp volume-to-diameter ratio was also significantly greater for advanced polyps. For polyps observed at three or more time points, most advanced polyps demonstrated an initial slower growth interval, followed by a period of more rapid growth. Conclusion Small colorectal polyps ultimately proving to be histopathologically advanced neoplasms demonstrated substantially faster growth and attained greater overall size compared with nonadvanced polyps. Clinical trial registration no. NCT00204867 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Dachman in this issue.

Growth rates and histopathological outcomes of small (6-9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal

BACKGROUND AND AIMS

The natural history of small polyps is not well established and rests on limited evidence from barium enema studies decades ago. Patients with one or two small polyps (6-9 mm) at screening CT colonography (CTC) are offered CTC surveillance at 3 years but may elect immediate colonoscopy. This practice allows direct observation of the growth of subcentimetre polyps, with histopathological correlation in patients undergoing subsequent polypectomy.

DESIGN

Of 11 165 asymptomatic patients screened by CTC over a period of 16.4 years, 1067 had one or two 6-9 mm polyps detected (with no polyps ≥10 mm). Of these, 314 (mean age, 57.4 years; M:F, 141:173; 375 total polyps) elected immediate colonoscopic polypectomy, and 382 (mean age 57.0 years; M:F, 217:165; 481 total polyps) elected CTC surveillance over a mean of 4.7 years. Volumetric polyp growth was analysed, with histopathological correlation for resected polyps. Polyp growth and regression were defined as volume change of ±20% per year, with rapid growth defined as +100% per year (annual volume doubling). Regression analysis was performed to evaluate predictors of advanced histology, defined as the presence of cancer, high-grade dysplasia (HGD) or villous components.

RESULTS

Of the 314 patients who underwent immediate polypectomy, 67.8% (213/314) harboured adenomas, 2.2% (7/314) with advanced histology; no polyps contained cancer or HGD. Of 382 patients who underwent CTC surveillance, 24.9% (95/382) had polyps that grew, while 62.0% (237/382) remained stable and 13.1% (50/382) regressed in size. Of the 58.6% (224/382) CTC surveillance patients who ultimately underwent colonoscopic resection, 87.1% (195/224) harboured adenomas, 12.9% (29/224) with advanced histology. Of CTC surveillance patients with growing polyps who underwent resection, 23.2% (19/82) harboured advanced histology vs 7.0% (10/142) with stable or regressing polyps (OR: 4.0; p<0.001), with even greater risk of advanced histology in those with rapid growth (63.6%, 14/22, OR: 25.4; p<0.001). Polyp growth, but not patient age/sex or polyp morphology/location were significant predictors of advanced histology.

CONCLUSION

Small 6-9 mm polyps present overall low risk to patients, with polyp growth strongly associated with higher risk lesions. Most patients (75%) with small 6-9 mm polyps will see polyp stability or regression, with advanced histology seen in only 7%. The minority of patients (25%) with small polyps that do grow have a 3-fold increased risk of advanced histology.

Definition of competence standards for optical diagnosis of diminutive colorectal polyps: European Society of Gastrointestinal Endoscopy (ESGE) Position Statement

BACKGROUND : The European Society of Gastrointestinal Endoscopy (ESGE) has developed a core curriculum for high quality optical diagnosis training for practice across Europe. The development of easy-to-measure competence standards for optical diagnosis can optimize clinical decision-making in endoscopy. This manuscript represents an official Position Statement of the ESGE aiming to define simple, safe, and easy-to-measure competence standards for endoscopists and artificial intelligence systems performing optical diagnosis of diminutive colorectal polyps (1 - 5 mm). METHODS : A panel of European experts in optical diagnosis participated in a modified Delphi process to reach consensus on Simple Optical Diagnosis Accuracy (SODA) competence standards for implementation of the optical diagnosis strategy for diminutive colorectal polyps. In order to assess the clinical benefits and harms of implementing optical diagnosis with different competence standards, a systematic literature search was performed. This was complemented with the results from a recently performed simulation study that provides guidance for setting alternative competence standards for optical diagnosis. Proposed competence standards were based on literature search and simulation study results. Competence standards were accepted if at least 80 % agreement was reached after a maximum of three voting rounds. RECOMMENDATION 1:  In order to implement the leave-in-situ strategy for diminutive colorectal lesions (1-5 mm), it is clinically acceptable if, during real-time colonoscopy, at least 90 % sensitivity and 80 % specificity is achieved for high confidence endoscopic characterization of colorectal neoplasia of 1-5 mm in the rectosigmoid. Histopathology is used as the gold standard.Level of agreement 95 %. RECOMMENDATION 2:  In order to implement the resect-and-discard strategy for diminutive colorectal lesions (1-5 mm), it is clinically acceptable if, during real-time colonoscopy, at least 80 % sensitivity and 80 % specificity is achieved for high confidence endoscopic characterization of colorectal neoplasia of 1-5 mm. Histopathology is used as the gold standard.Level of agreement 100 %. CONCLUSION : The developed SODA competence standards define diagnostic performance thresholds in relation to clinical consequences, for training and for use when auditing the optical diagnosis of diminutive colorectal polyps.

Analysis of dynamic molecular networks: the progression from colorectal adenoma to cancer

BACKGROUND

Colorectal cancer (CRC) is one of the deadliest cancers worldwide. It is the fourth most deadly cancer in the world with nearly 900,000 people die every year, the progression of polyps into cancer as one of its most common developmental pathways.

METHODS

This study obtained gene chip data collections from the Gene Expression Omnibus for colorectal adenoma (GSE8671) and colorectal cancer (GSE32323). Differentially expressed genes (DEGs) in normal tissue and different stages of CRC were analyzed for clustering, comparison, and visualization using R software. The Cytoscape plugin DyNetViewer was used to construct a dynamic protein-protein interaction network. Subsequently, through the Database for Annotation, Visualization and Integrated Discovery, the DEGs were functionally annotated and path enriched.

RESULTS

Our study found that the matrix metalloprotein family and chemokines were the key regulatory genes that drove CRC progression. The Wnt signaling pathway, chemokine signaling pathway, and CRC pathway were the pathological pathways for CRC. Maintenance played an important role in this process. In addition, the related nodes and pathways at various stages may be potential mechanisms for promoting dynamic CRC progression.

CONCLUSIONS

Our study provides a better understanding of the dynamic pattern of molecular interaction networks during CRC progression and provides relevant markers for more accurate screening of cancer in polyps.

Prediction of the severity of colorectal lesion by fecal hemoglobin concentration observed during previous test in the French screening program

BACKGROUND

The rate of positive tests using fecal immunochemical test (FIT) does not decrease with subsequent campaigns, but the positive predictive value of advanced neoplasia significantly decreases in subsequent campaign after a first negative test. A relationship between the fecal hemoglobin concentration (Fhb) and the opportunity to detect a colorectal cancer in subsequent campaign has been shown.

AIM

To predict the severity of colorectal lesions based on Fhb measured during previous colorectal cancer screening campaign.

METHODS

This etiological study included 293750 patients aged 50-74, living in Auvergne-Rhône-Alpes (France). These patients completed at least two FIT [test_(-1) and test₍₀₎] between June 2015 and December 2019. Delay between test_(-1) and test₍₀₎ was > 1 year and test_(-1) result was negative (< 150 ngHb/mL). The severity of colorectal lesions diagnosed at test₍₀₎ was described according to Fhb measured at test_(-1) [Fhb_(-1)]. The relationship between the severity classified in seven ordinal categories and the predictive factors was analyzed in an ordered multivariate polytomous regression model.

RESULTS

The test₍₀₎ positive rate was 4.0%, and the colonoscopy completion rate was 97.1% in 11594 patients who showed a positive test₍₀₎. The colonoscopy detection rate was 77.7% in those 11254 patients who underwent a colonoscopy. A total of 8748 colorectal lesions were detected (including 2182 low-risk-polyps, 2400 high-risk-polyp, and 502 colorectal cancer). The colonoscopy detection rate varied significantly with Fhb_(-1) [0 ngHb/mL: 75.6%, (0-50 ngHb/mL): 77.3%, (50-100 ngHb/mL): 88.7%, (100-150 ngHb/mL): 90.3%; P = 0.001]. People with a Fhb_(-1) within (100-150 ngHb/mL) (P = 0.001) were 2.6 (2.2; 3.0) times more likely to have a high severity level compared to those having a Fhb_(-1) value of zero. This risk was reduced by 20% in patients aged 55-59 compared to those aged < 55 [adjusted odds ratio: 0.8 (0.6; 1.0)].

CONCLUSION

The study showed that higher Fhb_(-1) is correlated to an increased risk of severity of colorectal lesions. This risk of severity increased among first-time participants (age < 55) and the elderly (≥ 70). To avoid the loss of chance in these age groups, the FIT positivity threshold should be reduced to 100 ngHb/mL. The other alternative would be to reduce the time between the two tests in these age groups from the current 2 years to 1 year.

Is there need for routine CT colonography after CT-verified uncomplicated diverticulitis of the sigmoid colon?

Background

Following an episode of acute diverticulitis, surgical guidelines commonly advise routine colonic follow-up to rule out underlying malignancy. However, as a CT of the abdomen is frequently performed during clinical work-up, the routine need for colonic follow-up has become debated.

Purpose

To evaluate the need for routine CT colonography after an episode of CT-verified uncomplicated sigmoid diverticulitis to rule out underlying colorectal malignancy.

Material and methods

This study retrospectively evaluated 312 patients routinely referred to colonic evaluation by CT colonography following an episode of acute diverticulitis. Patients were excluded if lacking diagnostic CT of the abdomen at time of diagnosis, if presenting with atypical colonic involvement, or if CT findings were suggestive of complicated disease (e.g., abscess or perforation). CT colonography exams were routinely reviewed by experienced abdominal radiology consultants on the day of the procedure. If significant polyps were detected, or if colorectal malignancy could not be excluded, patients were referred to same-day optical colonoscopy. For these patients, medical records were reviewed for optical colonoscopy results and histology reports if applicable.

Results

Among 223 patients with CT-verified uncomplicated sigmoid diverticulitis, no patients were found to have underlying colorectal malignancy. 27 patients were referred to optical colonoscopy based on CT colonography findings. 18 patients consequently underwent polypectomy, all with either hyperplastic or adenomatous histology.

Conclusions

This study indicates that routine colonic evaluation by CT colonography following an episode of CT-verified uncomplicated sigmoid diverticulitis may be unwarranted, and should arguably be reserved for patients with protracted or atypical clinical course.

PPV and Detection Rate of mt-sDNA Testing, FIT, and CT Colonography for Advanced Neoplasia: A Hierarchic Bayesian Meta-Analysis of the Noninvasive Colorectal Screening Tests

BACKGROUND. Noninvasive tests for colorectal cancer (CRC) screening and prevention limit the need for invasive colonoscopy to follow up positive test results. However, the relative performance characteristics of available noninvasive tests have not yet been adequately compared. OBJECTIVE. We performed a systematic review and meta-analysis to compare the diagnostic performance of the available noninvasive CRC screening tests, including multitarget stool DNA (mt-sDNA) testing, fecal immunochemical testing (FIT), and CT colonography (CTC), with an emphasis on comparison of PPV and detection rate (DR) for advanced neoplasia (AN; encompassing cases of advanced adenomas and CRC). EVIDENCE ACQUISITION. After systematic searches of MEDLINE and Google Scholar databases, 10 mt-sDNA, 27 CTC, and 88 FIT published screening studies involving 25,132, 33,493, and 2,355,958 asymptomatic adults, respectively, were included. Meta-analysis with hierarchic Bayesian modeling was conducted in accordance with Cochrane Collaboration and PRISMA guidelines to determine test positivity rates (TPRs) leading to optical colonoscopy, as well as PPVs and DRs for both AN and CRC. Different positivity thresholds were considered for FIT and CTC. EVIDENCE SYNTHESIS. Point estimates (with 95% credible intervals) from pooled Bayesian meta-analysis combining all thresholds for FIT and stratifying CTC results by a polyp size threshold of 6 mm or larger (CTC6) and 10 mm or larger (CTC10) were calculated. TPR was 13.5% (10.9-16.6%) for mt-sDNA testing, 6.4% (5.8-7.2%) for FIT, 13.4% (11.4-15.6%) for CTC6, and 6.6% (5.2-7.7%) for CTC10. AN PPV was 26.9% (95% credible interval, 21.8-33.2%) for mt-sDNA testing, 31.8% (29.3-34.5%) for FIT, 34.4% (27.2-41.0%) for CTC6, and 61.0% (54.0-70.0%) for CTC10. CRC PPV was 2.4% (1.5-3.9%) for mt-sDNA testing, 4.9% (4.3-5.3%) for FIT, 3.5% (2.5-4.8%) for CTC6, and 6.0% (4.3-8.0%) for CTC10. The DR for AN was 3.4% (95% credible interval, 2.5-4.8%) for mt-SDNA, 2.0% (1.8-2.3%) for FIT, 4.8% (4.0-6.5%) for CTC6, and 4.0% (3.0-4.6%) for CTC10. When FIT is restricted to a lower threshold (< 10 μg Hb/g feces), its performance profile is similar to that of mt-sDNA testing, although available data are limited. AN PPV odds ratios (relative to CTC10 as the reference) were 0.24 (95% credible interval, 0.17-0.33) for mt-sDNA testing, 0.30 (0.24-0.45) for FIT, and 0.33 (0.25-0.47) for CTC6. CONCLUSION. Among noninvasive CRC screening tests, CTC with a polyp size threshold of 10 mm or larger most effectively targets AN, preserving detection while also decreasing unnecessary colonoscopies compared with mt-sDNA testing and FIT. CLINICAL IMPACT. CTC performed with a polyp size threshold for colonoscopy referral set at 10 mm or larger represents the most effective and efficient noninvasive screening test for CRC prevention and detection.

Clinical Validation of BASIC Classification for the Resect and Discard Strategy for Diminutive Colorectal Polyps

BACKGROUND & AIMS

Blue-light imaging (BLI) is a chromoendoscopy technique that uses direct (not filtered) emission of blue light with short wavelength (410 nm) to increase visibility of microvascular pattern and superficial mucosa. A BLI-based classification system for colorectal polyps (also called BLI Adenomas Serrated International Classification, BASIC) has been created and was validated using still images or short videos. We aimed to validate BASIC in a clinical practice setting, using thresholds recommended by the American Society for Gastrointestinal Endoscopy for the resect and discard strategy as the reference standard.

METHODS

We studied 333 patients (mean age, 62.7±8.1 y; 176 men) who underwent screening colonoscopy from January through July 2019. Six endoscopists trained in BASIC participated in the study. All detected diminutive polyps were characterized by real-time BLI and categorized as adenoma or non-adenoma according to BASIC. All polyps were removed and evaluated by histopathology. The BLI-directed surveillance intervals (based on high-confidence characterization of polyps 5 mm or smaller and pathology feature for others) were compared with histology-directed surveillance intervals, according to United States Multi-society Task Force and European Society of Gastrointestinal Endoscopy recommendations. We calculated negative-predictive values of optical real-time analysis of diminutive rectosigmoid adenomas.

RESULTS

When we applied BASIC, 748 polyps smaller than 5 mm were categorized with 89% accuracy (95% CI, 85.9%-90.6%). BLI-directed surveillance was correct for 90% of patients according to the United States Multi-society task force criteria (95% CI, 86%-93%) and for 96% of patients according to European Society of Gastrointestinal Endoscopy criteria (95% CI, 93%-97%). The negative-predictive value for 302 polyps smaller than 5 mm, located in the rectosigmoid colon and evaluated with high confidence, based on histologic features of adenomatous polyps, was 91% (95% CI, 85%-95%).

CONCLUSIONS

Our analysis of data from 333 patients undergoing screen colonoscopies supports the validity of BASIC discriminating diminutive colorectal polyps with histologic features of adenomas from non-adenomas. This allows for the implementation of the resect and discard strategy based on BLI in clinical practice. ClinicalTrials.gov no: NCT03746171.

An international polypectomy practice survey

Background and study aims: In recent years, cold snare polypectomy (CSP) has been recommended as the preferred approach for removal of small and diminutive colorectal polyps. We conducted an international survey among endoscopists to understand the uptake of CSP and changes in polypectomy practice during recent years.Patients and methods: Endoscopists were invited through gastroenterology, colorectal surgery and endoscopy societies to participate in an online survey. The primary outcome was to identify the predominant polypectomy approach used to remove 4‒10 mm colorectal polyps. Secondary outcomes included the uptake of CSP in the past 5 years, current polypectomy practice patterns for 1‒20 mm polyps, practice changes in recent years, and perceived benefits/concerns related to different polypectomy techniques.Results: The survey was distributed internationally by nine societies and completed by 808 endoscopists (response rate 3.7%). CSP was the predominant polypectomy technique for 4‒5 mm polyps (67.0%, 95% CI, 63.7-70.2%) and 6‒10 mm polyps (55.2%, 95% CI, 51.8-58.6%). For 1‒3 mm polyps, cold forceps remained the predominant technique (78.4%, 95% CI, 75.6-81.3%), whereas hot snare polypectomy (HSP) remained the predominant technique for 10‒20 mm polyps (92.5%, 95% CI, 90.7-94.3%). 87.5% (95% CI, 85.2-89.8%) of endoscopists reported an increase in CSP use during the past 5 years.Conclusions: This survey found a substantial increase in CSP use during recent years. CSP has become the predominant polypectomy approach for 4‒10 mm colorectal polyps, while HSP remained the predominant approach for larger (10‒20 mm) polyps. Clinical practice patterns are well aligned with recently issued guideline recommendations.

[Colorectal cancer: role of imaging in screening]

CLINICAL PROBLEM

Colorectal cancer (CRC) is a major cause of cancer-related morbidity and mortality. Most colorectal cancers derive from benign precursor lesions, so-called adenomatous polyps, over a long period of time. Colorectal cancer screening is based on the detection of precancerous polyps and early stage CRC in asymptomatic individuals to reduce CRC incidence and mortality. The protective effect of screening programs can be improved by increasing the screening rates.

PRACTICAL RECOMMENDATIONS

Apart from the established examinations, CT colonography (CTC) has been proposed as an optional test for colorectal cancer screening. The detection rates of CTC for large polyps and cancer are similar to the ones of colonoscopy and superior to stool-based tests. CTC is therefore the radiological test of choice for the detection of colorectal neoplasia. It has replaced double contrast barium enema for almost all indications. As a minimally invasive procedure, CTC has a high safety profile and good patient acceptance. The evaluation of extracolonic organs in addition to the colon can increase examination efficacy. The option to choose CTC as a CRC screening test has the potential to increase the overall screening rates.

Conserved serum protein biomarkers associated with growing early colorectal adenomas

A major challenge for the reduction of colon cancer is to detect patients carrying high-risk premalignant adenomas with minimally invasive testing. As one step, we have addressed the feasibility of detecting protein signals in the serum of patients carrying an adenoma as small as 6-9 mm in maximum linear dimension. Serum protein biomarkers, discovered in two animal models of early colonic adenomagenesis, were studied in patients using quantitative mass-spectrometric assays. One cohort included patients bearing adenomas known to be growing on the basis of longitudinal computed tomographic colonography. The other cohort, screened by optical colonoscopy, included both patients free of adenomas and patients bearing adenomas whose risk status was judged by histopathology. The markers F5, ITIH4, LRG1, and VTN were each elevated both in this patient study and in the studies of the Pirc rat model. The quantitative study in the Pirc rat model had demonstrated that the elevated level of each of these markers is correlated with the number of colonic adenomas. However, the levels of these markers in patients were not significantly correlated with the total adenoma volume. Postpolypectomy blood samples demonstrated that the elevated levels of these four conserved markers persisted after polypectomy. Two additional serum markers rapidly renormalized after polypectomy: growth-associated CRP levels were enhanced only with high-risk adenomas, while PI16 levels, not associated with growth, were reduced regardless of risk status. We discuss biological hypotheses to account for these observations, and ways for these signals to contribute to the prevention of colon cancer.

Positive Predictive Value for Colorectal Lesions at CT Colonography: Analysis of Factors Impacting Results in a Large Screening Cohort

OBJECTIVE. The purpose of this study is to evaluate factors affecting the positive predictive value (PPV) for detecting colorectal lesions at CT colonography (CTC), using optical colonoscopy (OC) as the reference standard for concordance. MATERIALS AND METHODS. Consecutive CTC studies from a single screening program interpreted as positive for at least one detected colorectal lesion 6 mm or larger and sent for subsequent OC were analyzed according to per-polyp and per-patient results. Univariable and multivariable analysis of multiple input factors was performed. RESULTS. Of 1650 studies (median patient age, 59.7 years; 877 men and 773 women) with 2688 total CTC-detected lesions 6 mm or larger, the overall PPVs were 88.8% (2386/2688) by polyp and 90.8% (1499/1650) by patient. The by-polyp PPV was significantly higher for polypoid (91.2%; 1793/1965) versus flat or nonpolypoid (79.4%; 459/578) lesions (p < 0.0001). Overall per-patient PPVs were 72.3% (1193/1650) for any neoplasia 6 mm or larger and 38.8% (641/1650) for advanced neoplasia. PPVs for advanced neoplasia increased by CTC Reporting and Data System category: 5.8% (45/781) for C2, 67.1% (511/762) for C3, and 79.4% (85/107) for C4. PPVs for cancer also increased by CTC Reporting and Data System category: 0% (0/781) for C2, 2.2% (17/762) for C3, and 52.3% (56/107) for C4. On multivariable regression analysis, polyp morphologic type (flat vs polypoid) and diagnostic confidence were the strongest predictors of CTC-OC concordance. CTC PPV results are somewhat underestimated because 28.8% (87/302) of CTC-OC-discordant results were categorized as likely OC false-negatives at consensus review. CONCLUSION. Concordance between CTC and OC is high for relevant colorectal polyps and masses. Unlike stool-based tests that provide only a binary positive or negative result, CTC can specify the nature of the positive findings, resulting in much greater specificity and risk stratification for patient management decisions.

Diminutive Polyps With Advanced Histologic Features Do Not Increase Risk for Metachronous Advanced Colon Neoplasia

BACKGROUND & AIMS

With advances in endoscopic imaging, it is possible to differentiate adenomatous from hyperplastic diminutive (1-5 mm) polyps during endoscopy. With the optical Resect-and-Discard strategy, these polyps are then removed and discarded without histopathology assessment. However, failure to recognize adenomas (vs hyperplastic polyps), or discarding a polyp with advanced histologic features, could result in a patient being considered at low risk for metachronous advanced neoplasia, resulting in an inappropriately long surveillance interval. We collected data from international cohorts of patients undergoing colonoscopy to determine what proportion of patients are high risk because of diminutive polyps advanced histologic features and their risk for metachronous advanced neoplasia.

METHODS

We collected data from 12 cohorts (in the United States or Europe) of patients undergoing colonoscopy after a positive result from a fecal immunochemical test (FIT cohort, n = 34,221) or undergoing colonoscopies for screening, surveillance, or evaluation of symptoms (colonoscopy cohort, n = 30,123). Patients at high risk for metachronous advanced neoplasia were defined as patients with polyps that had advanced histologic features (cancer, high-grade dysplasia, ≥25% villous features), 3 or more diminutive or small (6-9 mm) nonadvanced adenomas, or an adenoma or sessile serrated lesion ≥10 mm. Using an inverse variance random effects model, we calculated the proportion of diminutive polyps with advanced histologic features; the proportion of patients classified as high risk because their diminutive polyps had advanced histologic features; and the risk of these patients for metachronous advanced neoplasia.

RESULTS

In 51,510 diminutive polyps, advanced histologic features were observed in 7.1% of polyps from the FIT cohort and 1.5% polyps from the colonoscopy cohort (P = .044); however, this difference in prevalence did not produce a significant difference in the proportions of patients assigned to high-risk status (0.8% of patients in the FIT cohort and 0.4% of patients in the colonoscopy cohort) (P = .25). The proportions of high-risk patients because of diminutive polyps with advanced histologic features who were found to have metachronous advanced neoplasia (17.6%) did not differ significantly from the proportion of low-risk patients with metachronous advanced neoplasia (14.6%) (relative risk for high-risk categorization, 1.13; 95% confidence interval 0.79-1.61).

CONCLUSION

In a pooled analysis of data from 12 international cohorts of patients undergoing colonoscopy for screening, surveillance, or evaluation of symptoms, we found that diminutive polyps with advanced histologic features do not increase risk for metachronous advanced neoplasia.

The Natural History of Colorectal Polyps: Overview of Predictive Static and Dynamic Features

For decades, colorectal screening strategies have been largely driven by static features, particularly polyp size. Although cross-sectional features of polyp size, morphology, and location are important determinants of clinical relevance before histology, they lack any dynamic information on polyp growth rates. Computed tomography colonography allows for in vivo surveillance of colorectal polyps, providing volumetric growth rates that are providing new insights into tumorigenesis. In this article, existing cross-sectional and longitudinal data on colorectal polyps are reviewed, with an emphasis on how these features may affect clinical relevance and patient management.

Effects of Training and Feedback on Accuracy of Predicting Rectosigmoid Neoplastic Lesions and Selection of Surveillance Intervals by Endoscopists Performing Optical Diagnosis of Diminutive Polyps

BACKGROUND & AIMS

Real-time differentiation of diminutive polyps (1-5 mm) during endoscopy could replace histopathology analysis. According to guidelines, implementation of optical diagnosis into routine practice would require it to identify rectosigmoid neoplastic lesions with a negative predictive value (NPV) of more than 90%, using histologic findings as a reference, and agreement with histology-based surveillance intervals for more than 90% of cases.

METHODS

We performed a prospective study with 39 endoscopists accredited to perform colonoscopies on participants with positive results from fecal immunochemical tests in the Bowel Cancer Screening Program at 13 centers in the Netherlands. Endoscopists were trained in optical diagnosis using a validated module (Workgroup serrAted polypS and Polyposis). After meeting predefined performance thresholds in the training program, the endoscopists started a 1-year program (continuation phase) in which they performed narrow band imaging analyses during colonoscopies of participants in the screening program and predicted histological findings with confidence levels. The endoscopists were randomly assigned to groups that received feedback or no feedback on the accuracy of their predictions. Primary outcome measures were endoscopists' abilities to identify rectosigmoid neoplastic lesions (using histology as a reference) with NPVs of 90% or more, and selecting surveillance intervals that agreed with those determined by histology for at least 90% of cases.

RESULTS

Of 39 endoscopists initially trained, 27 (69%) completed the training program. During the continuation phase, these 27 endoscopists performed 3144 colonoscopies in which 4504 diminutive polyps were removed. The endoscopists identified neoplastic lesions with a pooled NPV of 90.8% (95% confidence interval 88.6-92.6); their proposed surveillance intervals agreed with those determined by histologic analysis for 95.4% of cases (95% confidence interval 94.0-96.6). Findings did not differ between the group that did vs did not receive feedback. Sixteen endoscopists (59%) identified rectosigmoid neoplastic lesions with NPVs greater than 90% and selected surveillance intervals in agreement with those determined from histology for more than 90% of patients.

CONCLUSIONS

In a prospective study following a validated training module, we found that a selected group of endoscopists identified rectosigmoid neoplastic lesions with pooled NPVs greater than 90% and accurately selected surveillance intervals for more than 90% of patients over the course of 1 year. Providing regular interim feedback on the accuracy of neoplastic lesion prediction and surveillance interval selection did not lead to differences in those endpoints. Monitoring is suggested, as individual performance varied. ClinicalTrials.gov no: NCT02516748; Netherland Trial Register: NTR4635.

Structured reporting and quality control in CT colonography

Standardized recommended techniques for performing and reporting CT colonography (CTC) examinations were developed by a consensus of experts. Published reporting guidelines, known as the CT colonography reporting and data system supplemented by recently updated comprehensive recommendations were incorporated into the American College of Radiology (ACR) practice guidelines. The application of continuous quality improvement to the practice of CT was aided by the development of an ACR national data registry (NRDR) for CTC that addressed both process and outcome quality measures. These measures can be used to benchmark an institution's CTC practice as compared to all participants. This article will discuss the best practices for reporting CTC and describe the use of NRDR to foster quality CTC performance.

Lesions of All Types Exist in Colon Polyps of All Sizes

OBJECTIVES

Although large polyps are known to harbor more advanced neoplasia than small polyps, the extent of the relationship between size and type is not fully known. The study aim was to establish benchmarks for the prevalence of different histologic polyp types among varying size categories.

METHODS

The Miraca Life Sciences Database is an electronic repository of histopathologic patient records from private practices throughout the United States. We extracted the records of 483,998 unique patients who underwent colonoscopy with polypectomy between January 2008 and December 2014. A total of 550,811 polyps were stratified by their endoscopic size measurement. Polyps of each size were further stratified as hyperplastic polyp (HP), tubular adenoma (TA), tubulovillous adenoma (TVA), sessile serrated adenoma/polyp, and adenocarcinoma.

RESULTS

Of all 550,811 polyps, 447,343 (81%) were 1-9 mm in size, and 103,517 (19%) were 10 mm or larger. A fraction of 18,591/550,811 polyps (3.4%) harbored histologic features of advanced adenoma, such as TVA, high-grade dysplasia, or cancer. Of these, 4,725/18,591 (25%) occurred in polyps 1-9 mm and 13,868/18,591 (75%) occurred in polyps 10 mm or larger. The fractions of advanced adenoma were 0.6% (0.5-0.6%) in 1-5 mm polyps and 2.1% (2.0-2.2%) in 6-9 mm polyps, as compared to 13.4% (13.2-13.6%) in polyps 10 mm or larger. The frequency of HP significantly decreased with increasing polyp size, whereas the frequency of TA remained largely unaffected by polyp size.

CONCLUSIONS

While advanced histopathology was found more frequently in colorectal polyps of larger than smaller size, one quarter of all advanced histopathology existed in polyps of <10 mm.

TC Rectal Pathology: Findings at CT-Colonography

OBJECTIVE

To review the spectrum of benign and malignant rectal diseases, their findings on CT colonography, and their management.

CONCLUSION

Although CT colonography is not the first choice for the study of rectal disease, it is indicated in cases where optical colonoscopy is contraindicated or cannot be completed. Rectal lesions can go undetected because this anatomic area is difficult to evaluate; for this reason, it is essential to ensure optimal preparation and distension, moderate balloon insufflation, and careful 2D and 3D navigation with knowledge of the spectrum of rectal disease and its CT colonography signs.

New insights into the earliest stages of colorectal tumorigenesis

Tumors in the large intestine have been postulated to arise via a stepwise accumulation of mutations, a process that takes up to 20 years. Recent advances in lineage tracing and DNA sequencing, however, are revealing new evolutionary models that better explain the vast amount of heterogeneity observed within and across colorectal tumors. Areas covered: A review of the literature supporting a novel model of colorectal tumor evolution was conducted. The following commentary examines the basic science and clinical evidence supporting a modified view of tumor initiation and progression in the colon. Expert commentary: The proposed 'cancer punctuated equilibrium' model of tumor evolution better explains the variability seen within and across polyps of the colon and rectum. Small colorectal polyps (6-9mm) followed longitudinally by interval imaging with CT colonography have been reported to have multiple fates: some growing, some remaining static in size, and others regressing in size over time. This new model allows for this variability in growth behavior and supports the hypothesis that some tumors can be 'born to be bad' as originally postulated by Sottoriva and colleagues, with very early molecular events impacting tumor fitness and growth behavior in the later stages of the disease process.

Natural history of diminutive and small colorectal polyps: a systematic literature review

BACKGROUND AND AIMS

Diminutive (1-5 mm) and small (6-9 mm) polyps comprise 90% of detected lesions during colonoscopy and rarely contain advanced histology or colorectal cancer (CRC). Routine removal of these lesions results in a significant burden to colonoscopy programs. At the same time, the risk for progression of these polyps to CRC is unclear. We performed a systematic review to explore the natural history of diminutive and small colorectal polyps.

METHODS

We searched MEDLINE and EMBASE for studies investigating the natural history of colorectal polyps. Studies were considered eligible when they assessed patients with 1- to 9-mm polyps that were not treated with polypectomy and that underwent follow-up. We excluded studies in patients with inflammatory bowel disease, polyposis syndromes, and previously diagnosed CRC. We independently extracted study characteristics and evaluated CRC and advanced adenoma (size ≥ 10 mm, containing high-grade dysplasia or villous features) as outcome parameters.

RESULTS

Of 8775 retrieved studies, 9 studies with 721 patients were included that prospectively evaluated the evolution of 1- to 9-mm polyps. In 7 studies the average duration of observation was 2 to 3 years. There was only 1 study in which 1 small polyp might have progressed to cancer. Of 1034 adenomas sized 1 to 9 mm in those studies, 6% progressed to advanced adenomas over time.

CONCLUSIONS

Based on this systematic review, it appears that some 1- to 9-mm adenomas progress to advanced adenomas within 2 to 3 years. No information on long-term CRC transition rates was found. Defining the biologic significance of these polyps is needed to balance between benefits and harm of polypectomy. (PROSPERO database registration number: CRD42016036577.).

Potential pitfalls in the anorectal region during CT colonography: A discussion and pictorial overview of common pitfalls

Common potential anorectal pitfalls are presented with accompanying CT colonography images. Although most lesions are benign, care must be taken in not missing an underlying cancer.

CT Colonographic Screening of Patients With a Family History of Colorectal Cancer: Comparison With Adults at Average Risk and Implications for Guidelines

OBJECTIVE

The purposes of this study were to compare rates of lesion detection at CT colonographic (CTC) screening of adults without symptoms who had and who did not have a family history of colorectal cancer according to American Cancer Society guidelines and to consider the clinical implications.

MATERIALS AND METHODS

Over 134 months, consecutively registered CTC cohorts of adults without symptoms who had (n = 156; 88 [56.4%] women; 68 [43.6%] men; mean age, 56.3 years) and who did not have (n = 8857; 4757 [53.7%] women; 4100 [46.3%] men; mean age, 56.6 years) an American Cancer Society-defined family history of colorectal cancer (first-degree relative with diagnosis before age 60 years or two first-degree relatives with diagnosis at any age) were compared for relevant colorectal findings.

RESULTS

For the family history versus no family history cohorts, the frequency of all nondiminutive polyps (≥ 6 mm) reported at CTC was 23.7% versus 15.5% (p = 0.007); small polyps (6-9 mm), 13.5% versus 9.1% (p = 0.068); and large polyps (≥ 10 mm), 10.2% versus 6.5% (p = 0.068). The rate of referral for colonoscopy was greater for the family history cohort (16.0% vs 10.5%; p = 0.035). However, the frequencies of proven advanced adenoma (4.5% vs 3.2%; p = 0.357), nonadvanced adenoma (5.1% vs 2.6%; p = 0.070), and cancer (0.0% vs 0.4%; p = 0.999) were not significantly increased. The difference in positive rates between the two cohorts (11.5% vs 4.3%; p < 0.001) was primarily due to nonneoplastic findings of no colorectal cancer relevance, such as small hyperplastic polyps, diverticular disease, and false-positive CTC findings.

CONCLUSION

Although the overall CTC-positive and colonoscopy referral rates were higher in the family history cohort, the clinically relevant frequencies of advanced neoplasia and cancer were not sufficiently increased to preclude CTC screening. These findings support the use of CTC as a front-line screening option in adults with a family history of colorectal cancer.

Colorectal Findings at Repeat CT Colonography Screening after Initial CT Colonography Screening Negative for Polyps Larger than 5 mm

Purpose To determine the rate and types of polyps detected at repeat computed tomographic (CT) colonography screening after initial negative findings at CT colonography screening. Materials and Methods Among 5640 negative CT colonography screenings (no polyps ≥ 6 mm) performed before 2010 at one medical center, 1429 (25.3%; mean age, 61.4 years; 736 women, 693 men) patients have returned for repeat CT colonography screening (mean interval, 5.7 years ± 0.9; range, 4.5-10.7 years). Positive rates and histologic findings of initial and repeat screening were compared in this HIPAA-compliant, institutional review board-approved study. For all patients with positive findings at repeat CT colonography, the findings were directly compared against the initial CT colonography findings. Fisher exact, Pearson χ², and Student t tests were applied as indicated. Results Repeat CT colonography screening was positive for lesions 6 mm or larger in 173 (12.1%) adults (compared with 14.3% at initial CT colonography screening, P = .29). In the 173 patients, 29.5% (61 of 207) of nondiminutive polyps could be identified as diminutive at the initial CT colonography and 12.6% (26 of 207) were missed. Large polyps, advanced neoplasia (advanced adenomas and cancer), and invasive cancer were seen in 3.8% (55 of 1429), 2.8% (40 of 1429), and 0.14% (two of 1429), respectively, at follow-up, compared with 5.2% (P = .02), 3.2% (P = .52), and 0.45% (P = .17), respectively, at initial screening. Of 42 advanced lesions in 40 follow-up screenings, 33 (78.6%) were right sided and 22 (52.4%) were flat, compared with 45.4% (P < .001) and 11.3% (P < .001), respectively, at initial screening. Large right-sided serrated lesions were confirmed in 20 individuals (1.4%), compared with 0.5% (P < .001) confirmed at initial screening. Conclusion Positive rates for large polyps at repeat CT colonography screening (3.7%) were lower compared with those at initial screening (5.2%). However, more advanced right-sided lesions were detected at follow-up CT colonography, many of which were flat, serrated lesions. The cumulative findings support both the nonreporting of diminutive lesions and a 5-10-year screening interval. ^© RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on August 30, 2016.

Emerging stool-based and blood-based non-invasive DNA tests for colorectal cancer screening: the importance of cancer prevention in addition to cancer detection

Colorectal cancer (CRC) screening can be undertaken utilizing a variety of distinct approaches, which provides both opportunities and confusion. Traditionally, there has often been a trade-off between the degree of invasiveness of a screening test and its ability to prevent cancer, with fecal occult blood testing (FOBT) and optical colonoscopy (OC) at each end of the spectrum. CT colonography (CTC), although currently underutilized for CRC screening, represents an exception since it is only minimally invasive, yet provides accurate evaluation for advanced adenomas. More recently, the FDA approved a multi-target stool DNA test (Cologuard) and a blood-based test (Epi proColon) for average-risk CRC screening. This commentary will provide an overview of these two new non-invasive tests, including the clinical indications, mechanism of action, and diagnostic performance. Relevance to radiology practice, including a comparison with CTC, will also be discussed.

Texture Feature Extraction and Analysis for Polyp Differentiation via Computed Tomography Colonography

Image textures in computed tomography colonography (CTC) have great potential for differentiating non-neoplastic from neoplastic polyps and thus can advance the current CTC detection-only paradigm to a new level with diagnostic capability. However, image textures are frequently compromised, particularly in low-dose CT imaging. Furthermore, texture feature extraction may vary, depending on the polyp spatial orientation variation, resulting in variable results. To address these issues, this study proposes an adaptive approach to extract and analyze the texture features for polyp differentiation. Firstly, derivative (e.g. gradient and curvature) operations are performed on the CT intensity image to amplify the textures with adequate noise control. Then Haralick co-occurrence matrix (CM) is used to calculate texture measures along each of the 13 directions (defined by the first and second order image voxel neighbors) through the polyp volume in the intensity, gradient and curvature images. Instead of taking the mean and range of each CM measure over the 13 directions as the so-called Haralick texture features, Karhunen-Loeve transform is performed to map the 13 directions into an orthogonal coordinate system so that the resulted texture features are less dependent on the polyp orientation variation. These simple ideas for amplifying textures and stabilizing spatial variation demonstrated a significant impact for the differentiating task by experiments using 384 polyp datasets, of which 52 are non-neoplastic polyps and the rest are neoplastic polyps. By the merit of area under the curve of receiver operating characteristic, the innovative ideas achieved differentiation capability of 0.8016, indicating the CTC diagnostic feasibility.

Evolution of Screen-Detected Small (6-9 mm) Polyps After a 3-Year Surveillance Interval: Assessment of Growth With CT Colonography Compared With Histopathology

OBJECTIVES

Volumetric growth assessment has been proposed for predicting advanced histology at surveillance computed tomography (CT) colonography (CTC). We examined whether is it possible to predict which small (6-9 mm) polyps are likely to become advanced adenomas at surveillance by assessing volumetric growth.

METHODS

In an invitational population-based CTC screening trial, 93 participants were diagnosed with one or two 6-9 mm polyps as the largest lesion(s). They were offered a 3-year surveillance CTC. Participants in whom surveillance CTC showed lesion(s) of ≥6 mm were offered colonoscopy. Volumetric measurements were performed on index and surveillance CTC, and polyps were classified into growth categories according to ±30% volumetric change (>30% growth as progression, 30% growth to 30% decrease as stable, and >30% decrease as regression). Polyp growth was related to histopathology.

RESULTS

Between July 2012 and May 2014, 70 patients underwent surveillance CTC after a mean surveillance interval of 3.3 years (s.d. 0.3; range 3.0-4.6 years). In all, 33 (35%) of 95 polyps progressed, 36 (38%) remained stable, and 26 (27%) regressed, including an apparent resolution in 13 (14%) polyps. In 68 (83%) of the 82 polyps at surveillance, histopathology was obtained; 15 (47%) of 32 progressing polyps were advanced adenomas, 6 (21%) of 28 stable polyps, and none of the regressing polyps.

CONCLUSIONS

The majority of 6-9 mm polyps will not progress to advanced neoplasia within 3 years. Those that do progress to advanced status can in particular be found among the lesions that increased in size on surveillance CTC.

Defining the Risk of Small Polyps: Potential Value of CTC

Although the clinical importance of large colorectal polyps and the benign nature of diminutive polyps are generally accepted, elucidating the clinical significance of small polyps (6-9 mm) could have an enormous impact on colorectal cancer (CRC) screening. Serial volumetric measurement via CTC may be a valuable method for assessing changes in polyp size. With the recognition of alternative CRC pathways, a more precise understanding of the natural history of small colorectal polyps is needed and data such as those reported by Nolthenius contribute to that knowledge.

Computer tomography colonography participation and yield in patients under surveillance for 6-9 mm polyps in a population-based screening trial

Purpose

Surveillance CT colonography (CTC) is a viable option for 6-9 mm polyps at CTC screening for colorectal cancer. We established participation and diagnostic yield of surveillance and determined overall yield of CTC screening.

Material and methods

In an invitational CTC screening trial 82 of 982 participants harboured 6-9 mm polyps as the largest lesion(s) for which surveillance CTC was advised. Only participants with one or more lesion(s) ≥6 mm at surveillance CTC were offered colonoscopy (OC); 13 had undergone preliminary OC. The surveillance CTC yield was defined as the number of participants with advanced neoplasia in the 82 surveillance participants, and was added to the primary screening yield.

Results

Sixty-five of 82 participants were eligible for surveillance CTC of which 56 (86.2 %) participated. Advanced neoplasia was diagnosed in 15/56 participants (26.8 %) and 9/13 (69.2 %) with preliminary OC. Total surveillance yield was 24/82 (29.3 %). No carcinomas were detected. Adding surveillance results to initial screening CTC yield significantly increased the advanced neoplasia yield per 100 CTC participants (6.1 to 8.6; p < 0.001) and per 100 invitees (2.1 to 2.9; p < 0.001).

Conclusion

Surveillance CTC for 6-9 mm polyps has a substantial yield of advanced adenomas and significantly increased the CTC yield in population screening.

Key Points

• The participation rate in surveillance CT colonography (CTC) is 86 %.

• Advanced adenoma prevalence in a 6-9 mm CTC surveillance population is high.

• Surveillance CTC significantly increases the yield of population screening by CTC.

• Surveillance CTC for 6-9 mm polyps is a safe strategy.

• Surveillance CTC is unlikely to yield new important extracolonic findings.

Small Polyps at Endoluminal CT Colonography Are Often Seen But Ignored by Radiologists

OBJECTIVE

The objective of our study was to describe the characteristics of polyps viewed but then dismissed incorrectly by radiologists at endoluminal CT colonography (CTC), eye movements during these errors, and features provoking false-positive diagnoses.

MATERIALS AND METHODS

Forty-two radiologists viewed 30 endoluminal CTC videos, each depicting a polyp, while their eye movements were tracked. Half of the videos had computer-assisted detection (CAD), and half did not. Classification errors were defined when proven polyps were seen but dismissed. Eye movements during these errors and during correct polyp identifications were compared with multilevel modeling. Polyps were divided subsequently into "difficult to classify" and "easy to classify" using a classification error threshold of more than 15%. Polyp diameter, height, and subjective conspicuity and the proportion of time viewed were compared between groups.

RESULTS

Eye tracking revealed that 97% of false-negative polyp diagnoses were nonetheless preceded by the reader observing the polyp. The difficult polyps were significantly smaller than the easy polyps (mean diameter, 5.4 vs 8.2 mm, respectively p = 0.014) and were subjectively less conspicuous (median score, 4 vs 2; p = 0.0032). Readers spent proportionally less time viewing difficult polyps than viewing easy polyps (29.0% of the time they were on-screen vs 42.6%, respectively; p = 0.01) regardless of the presence of CAD.

CONCLUSION

Even small and subjectively inconspicuous polyps attract reader gaze, but they are nonetheless ignored. These errors are made rapidly even with CAD. Efforts to improve reader performance at CTC should focus on decision making rather than detection alone.

Colon capsule versus CT colonography in patients with incomplete colonoscopy: a prospective, comparative trial

OBJECTIVE

In case of incomplete colonoscopy, several radiologic methods have traditionally been used, but more recently, capsule endoscopy was also shown to be accurate. Aim of this study was to compare colon capsule endoscopy (CCE) and CT colonography (CTC) in a prospective cohort of patients with incomplete colonoscopy.

DESIGN

Consecutive patients with a previous incomplete colonoscopy underwent CCE and CTC followed by colonoscopy in case of positive findings on either test (polyps/mass lesions ≥6 mm). Clinical follow-up was performed in the other cases to rule out missed cancer. CTC was performed after colon capsule excretion or 10-12 h postingestion. Since the gold standard colonoscopy was performed only in positive cases, diagnostic yield and positive predictive values of CCE and CTC were used as study end-points.

RESULTS

100 patients were enrolled. CCE and CTC were able to achieve complete colonic evaluation in 98% of cases. In a per-patient analysis for polyps ≥6 mm, CCE detected 24 patients (24.5%) and CTC 12 patients (12.2%). The relative sensitivity of CCE compared to CTC was 2.0 (95% CI 1.34 to 2.98), indicating a significant increase in sensitivity for lesions ≥6 mm. Of larger polyps (≥10 mm), these values were 5.1% for CCE and 3.1% for CTC (relative sensitivity: 1.67 (95% CI 0.69 to 4.00)). Positive predictive values for polyps ≥6 mm and ≥10 mm were 96% and 85.7%, and 83.3% and 100% for CCE and CTC, respectively. No missed cancer occurred at clinical follow-up of a mean of 20 months.

CONCLUSIONS

CCE and CTC were of comparable efficacy in completing colon evaluation after incomplete colonoscopy; the overall diagnostic yield of colon capsule was superior to CTC.

TRIAL REGISTRATION NUMBER

NCT01525940.

Virtual gastrointestinal colonoscopy in combination with large bowel endoscopy: Clinical application

Although colorectal cancer (CRC) has no longer been the leading cancer killer worldwide for years with the exponential development in computed tomography (CT) or magnetic resonance imaging, and positron emission tomography/CT as well as virtual colonoscopy for early detection, the CRC related mortality is still high. The objective of CRC screening is to reduce the burden of CRC and thereby the morbidity and mortality rates of the disease. It is believed that this goal can be achieved by regularly screening the average-risk population, enabling the detection of cancer at early, curable stages, and polyps before they become cancerous. Large-scale screening with multimodality imaging approaches plays an important role in reaching that goal to detect polyps, Crohn’s disease, ulcerative colitis and CRC in early stage. This article reviews kinds of presentative imaging procedures for various screening options and updates detecting, staging and re-staging of CRC patients for determining the optimal therapeutic method and forecasting the risk of CRC recurrence and the overall prognosis. The combination use of virtual colonoscopy and conventional endoscopy, advantages and limitations of these modalities are also discussed.

CT Colonography Reporting and Data System (C-RADS): benchmark values from a clinical screening program

OBJECTIVE

The CT Colonography Reporting and Data System (C-RADS) is a well-recognized standard for reporting findings at CT colonography (CTC). However, few data on benchmark values for clinical performance have been published to date, especially for screening. The purpose of this study was to establish baseline C-RADS values for CTC screening.

SUBJECTS AND METHODS

From 2005 to 2011, 6769 asymptomatic adults (3110 men and 3659 women) 50-79 years old (mean [± SD] age, 56.7 ± 6.1 years) were enrolled for first-time CTC screening at a single center. CTC results were prospectively classified according to C-RADS for both colorectal and extracolonic findings. C-RADS classification rates and outcomes for positive patients were analyzed.

RESULTS

C-RADS classification rates for colorectal evaluation were C0 (0.7%), C1 (85.0%), C2 (8.6%), C3 (5.2%), and C4 (0.6%). Overall, 14.3% of subjects were positive (C2-C4), and positive findings were more frequent among men (17.5%) than women (11.6%; p < 0.0001). Positivity also increased with age, from 13.4% of patients 50-64 years old to 21.8% of patients 65-79 years old (p < 0.0001). Regarding extracolonic evaluation, 86.6% of patients were either negative for extracolonic findings or had unimportant extracolonic findings (E1 or E2). Likely unimportant but indeterminate extracolonic findings where further workup might be indicated (E3) were found in 11.3% of patients, whereas 2.1% had likely important extracolonic findings (E4). Overall, E3 and E4 rates were increased for older (p < 0.0001) and female (p = 0.008) cohorts.

CONCLUSION

C-RADS results from our initial experience with CTC screening may serve as an initial benchmark for program comparison and quality assurance measures.

Volumetric texture features from higher-order images for diagnosis of colon lesions via CT colonography

PURPOSE

Differentiation of colon lesions according to underlying pathology, e.g., neoplastic and non-neoplastic lesions, is of fundamental importance for patient management. Image intensity-based textural features have been recognized as useful biomarker for the differentiation task. In this paper, we introduce texture features from higher-order images, i.e., gradient and curvature images, beyond the intensity image, for that task.

METHODS

Based on the Haralick texture analysis method, we introduce a virtual pathological model to explore the utility of texture features from high-order differentiations, i.e., gradient and curvature, of the image intensity distribution. The texture features were validated on a database consisting of 148 colon lesions, of which 35 are non-neoplastic lesions, using the support vector machine classifier and the merit of area under the curve (AUC) of the receiver operating characteristics.

RESULTS

The AUC of classification was improved from 0.74 (using the image intensity alone) to 0.85 (by also considering the gradient and curvature images) in differentiating the neoplastic lesions from non-neoplastic ones, e.g., hyperplastic polyps from tubular adenomas, tubulovillous adenomas and adenocarcinomas.

CONCLUSIONS

The experimental results demonstrated that texture features from higher-order images can significantly improve the classification accuracy in pathological differentiation of colorectal lesions. The gain in differentiation capability shall increase the potential of computed tomography colonography for colorectal cancer screening by not only detecting polyps but also classifying them for optimal polyp management for the best outcome in personalized medicine.

Noncathartic CT colonography to screen for colorectal neoplasia in subjects with a family history of colorectal cancer

PURPOSE

To prospectively assess the diagnostic performance of noncathartic computed tomographic (CT) colonography in the detection of clinically relevant colorectal lesions (≥6 mm polyps or masses) in a well-defined cohort of first-degree relatives of patients with colorectal cancer (CRC), using colonoscopy and histologic review as the standard of reference.

MATERIALS AND METHODS

Institutional review board approval was obtained, and all subjects provided written informed consent. Consecutive patients admitted with CRC (index cases) were prospectively evaluated, and those who agreed to contact their first-degree relatives who were at least 40 years old were included. Available first-degree relatives were invited to undergo noncathartic CT colonography (200 mL of diatrizoate meglumine and diatrizoate sodium). Colonoscopy was performed the following day, and findings from CT colonography were disclosed for each segment. Sensitivity, specificity, and positive and negative predictive values of CT colonography were assessed for detecting subjects with any lesion at least 6 mm, any lesion at least 10 mm, and advanced neoplasia at least 6 mm. Colonoscopy with segmental unblinding and histologic diagnosis were used as the standard of reference. Matching between findings from CT colonography and colonoscopy was allowed when lesions were located in the same or adjacent colon segments and when the size difference was 50% or less.

RESULTS

Three hundred four first-degree relatives (median age, 47 years; age range, 40-79 years; 46.7% women) identified from 221 index cases were included. Overall, CT colonography helped identify 17 of 22 subjects with polyps measuring at least 6 mm (sensitivity, 0.77; 95% confidence interval [CI]: 0.59, 0.95) and helped correctly classify as negative 278 of 282 subjects without lesions measuring at least 6 mm (specificity, 0.99; 95% CI: 0.97, 1.00). CT colonography helped detect eight of nine subjects with polyps measuring at least 10 mm as well as eight of nine subjects with advanced neoplasia measuring at least 6 mm (sensitivity, 0.89 for both). Per-subject positive and negative predictive values for lesions measuring at least 6 mm were 0.81 (17 of 21 subjects; 95% CI: 0.65, 0.97) and 0.98 (282 of 287 subjects; 95% CI: 0.96, 0.99), respectively.

CONCLUSION

Noncathartic CT colonography is an effective screening method in first-degree relatives of patients with CRC.

Noncathartic CT colonography: Image quality assessment and performance and in a screening cohort

OBJECTIVE

Cathartic bowel preparation is a major barrier for colorectal cancer screening. We examined noncathartic CT colonography (CTC) quality and performance using four similar bowel-tagging regimens in an asymptomatic screening cohort.

SUBJECTS AND METHODS

This prospective study included 564 asymptomatic subjects who underwent noncathartic CTC without dietary modification but with 21 g of barium with or without iodinated oral contrast material (four regimens). The quality of tagging with oral agents was evaluated. A gastrointestinal radiologist evaluated examinations using primary 2D search supplemented by electronic cleansing (EC) and 3D problem solving. Results were compared with complete colonoscopy findings after bowel purgation and with retrospective unblinded evaluation in 556 of the 564 (99%) subjects.

RESULTS

Of the 556 subjects, 7% (37/556) and 3% (16/556) of patients had 52 and 20 adenomatous polyps ≥ 6 and ≥ 10 mm, respectively. The addition of iodine significantly improved the percentage of labeled stool (p ≤ 0.0002) and specificity (80% vs 89-93%, respectively; p = 0.046). The overall sensitivity of noncathartic CTC for adenomatous polyps ≥ 6 mm was 76% (28/37; 95% CI, 59-88%), which is similar to the sensitivity of the iodinated regimens with most patients (sensitivity: 231 patients, 74% [14/19; 95% CI, 49-91%]; 229 patients, 80% [12/15; 95% CI, 52-96%]). The negative predictive value was 98% (481/490), and the lone cancer was detected (0.2%, 1/556). EC was thought to improve conspicuity of 10 of 21 visible polyps ≥ 10 mm.

CONCLUSION

In this prospective study of asymptomatic subjects, the per-patient sensitivity of noncathartic CTC for detecting adenomas ≥ 6 mm was approximately 76%. Inclusion of oral iodine contrast material improves examination specificity and the percentage of labeled stool. EC may improve polyp conspicuity.

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.

Ethanol-induced mast cell-mediated inflammation leads to increased susceptibility of intestinal tumorigenesis in the APC Δ468 min mouse model of colon cancer

BACKGROUND

Chronic and frequent alcohol (ethanol [EtOH]) intake has been associated with an increased incidence of several types of cancers including breast, mouth, throat, esophageal, stomach, and colorectal (CRC). The underlying mechanism of this deleterious carcinogenic effect of alcohol has not been clearly established but inflammation may be 1 unifying feature of these cancers. We have recently shown that intestinal mast cells play a central role in intestinal carcinogenesis. In this study, we tested our hypothesis that mast cell-mediated inflammation is 1 underlying mechanism by which chronic alcohol promotes intestinal tumorigenesis.

METHODS

APC(Δ468) mice were fed either an alcohol-containing Nanji liquid diet or isocaloric dextrose-containing Nanji diet for 10 weeks and then sacrificed to collect small and large intestine samples. Assessments of tumor number and size as well as mast cell number and mast cell activity and histology score for invasion were compared between Control (dextrose-fed) and alcohol-fed APC(∆468) mice. The effect of alcohol on mast cell-mediated tumor migration was also assessed using an in vitro migration assay.

RESULTS

Alcohol feeding increased both polyp number and size within both the small and the large intestines of APC(∆468) mice. Only alcohol-fed mice showed evidence of tumor invasion. Chronic alcohol feeding also resulted in an increased mast cell number and activity in tumor stroma and invading borders. In vitro migration assay showed that alcohol significantly increases mast cell-mediated tumor migration in vitro.

CONCLUSIONS

Our data show that chronic alcohol intake promotes: (i) intestinal tumorigenesis and tumor invasion in genetically susceptible mice; (ii) increases in polyp-associated mast cells; and (iii) mast cell-mediated tumor migration in vitro. Both our in vivo and in vitro studies suggest that mast cell-mediated inflammation could be 1 mechanism by which alcohol promotes carcinogenesis.

Assessment of volumetric growth rates of small colorectal polyps with CT colonography: a longitudinal study of natural history

BACKGROUND

The clinical relevance and in-vivo growth rates of small (6-9 mm) colorectal polyps are not well established. We aimed to assess the behaviour of such polyps with CT colonography assessments.

METHODS

In this longitudinal study, we enrolled asymptomatic adults undergoing routine colorectal cancer screening with CT colonography at two medical centres in the USA. Experienced investigators (PJP, DHK, JLH) measured volumes and maximum linear sizes of polyps in vivo with CT colonography scans at baseline and surveillance follow-up. We defined progression, stability, and regression on the basis of a 20% volumetric change per year from baseline (20% or more growth classed as progression, 20% growth to -20% reduction classed as stable, and -20% or more reduction classed as regression). We compared findings with histological subgroups confirmed after colonoscopy when indicated. This study is registered with ClinicalTrials.gov, number NCT00204867.

FINDINGS

Between April, 2004, and June, 2012, we screened 22,006 asymptomatic adults and included 243 adults (mean age 57·4 years [SD 7·1] and median age 56 years [IQR 52-61]; 106 [37%] women), with 306 small colorectal polyps. The mean surveillance interval was 2·3 years (SD 1·4; range 1-7 years; median 2·0 years [IQR 1·1-2·3]). 68 (22%) of 306 polyps progressed, 153 (50%) were stable, and 85 (28%) regressed, including an apparent resolution in 32 (10%) polyps. We established immediate histology in 131 lesions on colonoscopy after final CT colonography. 21 (91%) of 23 proven advanced adenomas progressed, compared with 31 (37%) of 84 proven non-advanced adenomas, and 15 (8%) of 198 other lesions (p<0·0001). The odds ratio for a growing polyp at CT colonography surveillance to become an advanced adenoma was 15·6 (95% CI 7·6-31·7) compared with 6-9 mm polyps detected and removed at initial CT colonography screening (without surveillance). Mean polyp volume change was a 77% increase per year for 23 proven advanced adenomas and a 16% increase per year for 84 proven non-advanced adenomas, but a 13% decrease per year for all proven non-neoplastic or unresected polyps (p<0·0001). An absolute polyp volume of more than 180 mm(3) at surveillance CT colonography identified proven advanced neoplasia (including one delayed cancer) with a sensitivity of 92% (22 of 24 polyps), specificity of 94% (266 of 282 polyps), positive-predictive value of 58% (22 of 38 polyps), and negative-predictive value of 99% (266 of 268 polyps). Only 16 (6%) of the 6-9 mm polyps exceeded 10 mm at follow-up.

INTERPRETATION

Volumetric growth assessment of small colorectal polyps could be a useful biomarker for determination of clinical importance. Advanced adenomas show more rapid growth than non-advanced adenomas, whereas most other small polyps remain stable or regress. Our findings might allow for less invasive surveillance strategies, reserving polypectomy for lesions that show substantial growth. Further research is needed to provide more information regarding the ultimate fate of unresected small polyps without significant growth.

FUNDING

US National Institutes of Health, National Cancer Institute.