Endoscopic Assessment of Local Resectability of Colorectal Malignancies

Background

The endoscopic assessment of colorectal malignancies primarily aims at deciding on the local resectability. Local resectability is defined by the risk of lymphonodal metastasis.

Summary

The gross morphology as well as the surface and vessel patterns provide valuable information prior to endoscopic resection. Various classifications have been standardized to assist endoscopists during endoscopic assessment.

Key Message

The macroscopic assessment of colorectal malignancies should include the Paris and laterally spreading tumor (LST) classification as well as chromoendoscopic assessments such as Kudo's pit pattern and the Japanese NBI Expert Team classifications to describe the vessel and surface patterns.

Evaluating the Efficacy of Resect-and-Discard and Resect-and-Retrieve Strategies for Diminutive Colonic Polyps

BACKGROUND AND OBJECTIVES

Diminutive polyps present a unique challenge in colorectal cancer (CRC) prevention strategies. This study aims to assess the characteristics and variables of diminutive polyps in a Romanian cohort, intending to develop a combined resect-and-retrieve or resect-and-discard strategy that reduces the need for an optical diagnosis.

MATERIALS AND METHODS

A prospective cohort study was conducted at two endoscopy centers in Romania from July to December 2021. Adult patients undergoing colonoscopies where polyps were identified and resected were included. Endoscopic procedures employed advanced diagnostic features, including blue-light imaging (BLI) and narrow-band imaging (NBI). Logistic regression analysis was utilized to determine factors impacting the probability of adenomatous polyps with high-grade dysplasia (HGD).

RESULTS

A total of 427 patients were included, with a mean age of 59.42 years (±11.19), predominantly male (60.2%). The most common indication for a colonoscopy was lower gastrointestinal symptoms (42.6%), followed by screening (28.8%). Adequate bowel preparation was achieved in 87.8% of cases. The logistic regression analysis revealed significant predictors of HGD in adenomatous polyps: age (OR = 1.05, 95% CI: 1.01-1.08, p = 0.01) and polyp size (>5 mm vs. ≤5 mm, OR = 4.4, 95% CI: 1.94-10.06, p < 0.001). Polyps classified as Paris IIa, Ip, and Isp were significantly more likely to harbor HGD compared to the reference group (Is), with odds ratios of 6.05, 3.68, and 2.7, respectively.

CONCLUSIONS

The study elucidates significant associations between the presence of HGD in adenomatous polyps and factors such as age, polyp size, and Paris classification. These findings support the feasibility of a tailored approach in the resect-and-discard and resect-and-retrieve strategies for diminutive polyps, potentially optimizing CRC prevention and intervention practices. Further research is warranted to validate these strategies in broader clinical settings.

Advances in CRC Prevention: Screening and Surveillance

Colorectal cancer (CRC) is among the most commonly diagnosed cancers and causes of death from cancer across the world. CRC can, however, be detected in asymptomatic patients at a curable stage, and several studies have shown lower mortality among patients who undergo screening compared with those who do not. Using colonoscopy in CRC screening also results in the detection of precancerous polyps that can be directly removed during the procedure, thereby reducing the incidence of cancer. In the past decade, convincing evidence has appeared that the effectiveness of colonoscopy as CRC prevention tool is associated with the quality of the procedure. This review aims to provide an up-to-date overview of recent efforts to improve colonoscopy effectiveness by enhancing detection and improving the completeness and safety of resection of colorectal lesions.

Polyp characterization at colonoscopy: Clinical implications

Although advancements in endoscopic imaging of colorectal mucosa have outstripped the pace of research in the field, the potential clinical applications of these novel technologies are promising. Chief among these is the ability to diagnose colorectal polyps in vivo. This feature appears most applicable to diminuitive polyps, which have very little malignant potential yet represent over 70% of resected polyps. In an ideal application, the capability to predict diminutive hyperplastic polyp histology in vivo precludes the need for excision whereas dimunitive adenomas do require excision, but not necessarily histopathologic analysis if the diagnosis is made in vivo with adequate confidence. However, the vast array of new advanced imaging modalities and polyp classification tools have been difficult to reconcile. We aim to highlight the current status of real-time colorectal polyp diagnosis and identify the barriers that remain to its widespread implementation.

Morphological classifications of gastrointestinal lesions

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

Polyp Resection - Controversial Practices and Unanswered Questions

Detection and complete removal of precancerous neoplastic polyps are central to effective colorectal cancer screening. The prevalence of neoplastic polyps in the screening population in the United States is likely >50%. However, most persons with neoplastic polyps are never destined to develop cancer, and do not benefit for finding and removing polyps, and may only be harmed by the procedure. Further 70-80% of polyps are diminutive (≤5 mm) and such polyps almost never contain cancer. Given the questionable benefit, the high-cost and the potential risk changing our approach to the management of diminutive polyps is currently debated. Deemphasizing diminutive polyps and shifting our efforts to detection and complete removal of larger and higher-risk polyps deserves discussion and study. This article explores three controversies, and emerging concepts related to endoscopic polyp resection. First, we discuss challenges of optical resect-and-discard strategy and possible alternatives. Second, we review recent studies that support the use of cold snare resection for ≥5 mm polyps. Thirdly, we examine current evidence for prophylactic clipping after resection of large polyps.

Risk of cancer in small and diminutive colorectal polyps

The prevalence of cancer in small and diminutive polyps is relevant to "resect and discard" and CT colonography reporting recommendations. We evaluated a prospectively collected colonoscopy polyp database to identify polyps <10mm and those with cancer or advanced histology (high-grade dysplasia or villous elements). Of 32,790 colonoscopies, 15,558 colonoscopies detected 42,630 polyps <10mm in size. A total of 4790 lesions were excluded as they were not conventional adenomas or serrated class lesions. There were 23,524 conventional adenomas <10mm of which 22,952 were tubular adenomas. There were 14,316 serrated class lesions of which 13,589 were hyperplastic polyps and the remainder were sessile serrated polyps. Of all conventional adenomas, 96 had high-grade dysplasia including 0.3% of adenomas ≤5mm in size and 0.8% of adenomas 6-9mm in size. Of all conventional adenomas, 2.1% of those ≤5mm in size and 5.6% of those 6-9mm in size were advanced. Among 36,107 polyps ≤5mm in size and 6523 polyps 6-9mm in size, there were no cancers. These results support the safety of resect and discard as well as current CT colonography reporting recommendations for small and diminutive polyps.

Colonic polyp histopathology and location in a community-based sample of older adults

Background

Colorectal cancer and its precursors are highly prevalent in developed countries. Estimates in the available literature for prevalence of right-sided-only lesions vary between 20.5 and 48.1 %, with association with female gender and advancing age. Since the original polyp studies, premalignant potential of sessile serrated adenomas has been described and screening utilization of colonoscopy in men, women, and older adults has increased. This study describes the histopathology and distribution of colorectal polyps by age and gender in the post-screening era.

Methods

A registry of biopsies performed during colonoscopy for adults aged 50+ years in 2002-2012 was created using pathology reports from an independent, regional laboratory. Age, histopathology, and polyp location(s) were included. A subgroup analysis was performed for sessile serrated adenomas for 2007-2012. Distributions of histopathology and polyp location were described by age and gender. Statistical comparisons are made using chi-square tests.

Results

13,881 patients (55.5 % male, 44.5 % female), aged 50-95 years (median = 62) were identified. Most patients (59.9 %) had adenomas. Single and multiple adenomas were more common in men than women (57.7 % vs 42.3 %, p < .0001 and 62.2 % vs 37.8 %, p < .001), and with advancing age (60.4 % for ages 50- < 60, 63.4 % for ages 60- < 70, 65 % for ages 70- < 80, and 68.9 % for ages >80). Villous adenomas (n = 545; 3.6 %), dysplasia (n = 49; 0.4 %), and invasive carcinoma (n = 22; 0.2 %) were rare. Sessile serrated adenomas were uncommon (n = 417, 4.5 %), with greater prevalence in women than men (5.1 % vs 4 %, p = 0.02). Patients aged 70- < 80 were more likely to have multiple polyps than those aged 50- < 60 (OR 1.17, 95 % CI 1.03–1.32, p = 0.018 and OR 1.27, 95 % CI 1.10–1.46, p = .001). Most polyps were from ascending and/or transverse colon (n = 8095; 58.3 %). When location was stratified by sex only, men had more polyps than women at each location except the sigmoid and rectum. Further stratification by age of location and sex revealed statistically significant differences (age 50- < 60, p < .0001, age 60- < 70, p = .0227, age 70- < 80, p = .0298, age 80+, p = .0018).

Conclusions

This large community-based sample contributes to understanding of colonic neoplasia. The high prevalence of right and transverse lesions supports ongoing use of colonoscopy over sigmoidoscopy for screening examinations.

Screening for Colorectal Cancer Using a Multitarget Stool DNA Test: Modeling the Effect of the Intertest Interval on Clinical Effectiveness

BACKGROUND

A multitarget stool DNA (mt-sDNA) test was recently approved for colorectal cancer (CRC) screening for men and women, aged ≥ 50 years, at average risk of CRC. The guidelines currently recommend a 3-year interval for mt-sDNA testing in the absence of empirical data. We used clinical effectiveness modeling to project decreases in CRC incidence and related mortality associated with mt-sDNA screening to help inform interval setting.

MATERIALS AND METHODS

The Archimedes model (Archimedes Inc., San Francisco, CA) was used to conduct a 5-arm, virtual, clinical screening study of a population of 200,000 virtual individuals to compare the clinical effectiveness of mt-sDNA screening at 1-, 3-, and 5-year intervals compared with colonoscopy at 10-year intervals and no screening for a 30-year period. The study endpoints were the decrease in CRC incidence and related mortality of each strategy versus no screening. Cost-effectiveness ratios (US dollars per quality-adjusted life year [QALY]) of mt-sDNA intervals were calculated versus no screening.

RESULTS

Compared with 10-year colonoscopy, annual mt-sDNA testing produced similar reductions in CRC incidence (65% vs. 63%) and related mortality (73% vs. 72%). mt-sDNA testing at 3-year intervals reduced the CRC incidence by 57% and CRC mortality by 67%, and mt-sDNA testing at 5-year intervals reduced the CRC incidence by 52% and CRC mortality by 62%. At an average price of $600 per test, the annual, 3-year, and 5-year mt-sDNA screening costs would be $20,178, $11,313, and $7388 per QALY, respectively, compared with no screening.

CONCLUSION

These data suggest that screening every 3 years using a multitarget mt-sDNA test provides reasonable performance at acceptable cost.

Addressing overdiagnosis and overtreatment in cancer: a prescription for change

A vast range of disorders--from indolent to fast-growing lesions--are labelled as cancer. Therefore, we believe that several changes should be made to the approach to cancer screening and care, such as use of new terminology for indolent and precancerous disorders. We propose the term indolent lesion of epithelial origin, or IDLE, for those lesions (currently labelled as cancers) and their precursors that are unlikely to cause harm if they are left untreated. Furthermore, precursors of cancer or high-risk disorders should not have the term cancer in them. The rationale for this change in approach is that indolent lesions with low malignant potential are common, and screening brings indolent lesions and their precursors to clinical attention, which leads to overdiagnosis and, if unrecognised, possible overtreatment. To minimise that potential, new strategies should be adopted to better define and manage IDLEs. Screening guidelines should be revised to lower the chance of detection of minimal-risk IDLEs and inconsequential cancers with the same energy traditionally used to increase the sensitivity of screening tests. Changing the terminology for some of the lesions currently referred to as cancer will allow physicians to shift medicolegal notions and perceived risk to reflect the evolving understanding of biology, be more judicious about when a biopsy should be done, and organise studies and registries that offer observation or less invasive approaches for indolent disease. Emphasis on avoidance of harm while assuring benefit will improve screening and treatment of patients and will be equally effective in the prevention of death from cancer.

A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening

BACKGROUND & AIMS

A "resect and discard" policy has been proposed for diminutive polyps detected by screening colonoscopy, because hyperplastic and adenomatous polyps can be distinguished, in vivo, by using narrow-band imaging (NBI). We modeled the cost-effectiveness of this policy.

METHODS

Markov modeling was used to compare the cost-effectiveness of universal pathology evaluations with a resect and discard policy for colonoscopy screening. In a resect and discard approach, diminutive lesions (≤5 mm), classified by endoscopy with high confidence, were not analyzed by a pathologist. Base case assumptions of an 84% rate of high-confidence classification, with a sensitivity and specificity for adenomas of 94% and 89%, respectively, were used. Census data were used to project outputs of the model onto the US population, assuming 23% as the current rate of adherence to a colonoscopy screening.

RESULTS

With universal referral of resected polyps to pathology, colonoscopy screening costs an estimated $3222/person, with a gain of 51 days/person. Endoscopic polypectomy accounted for $179/person, of which $46/person was related to pathology examination. Adoption of a resect and discard policy for eligible diminutive polyps resulted in a savings of $25/person, without any meaningful effect on screening efficacy. Projected onto the US population, this approach would result in an undiscounted annual savings of $33 million. In the sensitivity analysis, the rate of high-confidence diagnosis and the accuracy for endoscopic polyp determination were the most meaningful variables.

CONCLUSIONS

In a simulation model, a resect and discard strategy for diminutive polyps detected by screening colonoscopy resulted in a substantial economic benefit without an impact on efficacy.

An evidence-based microsimulation model for colorectal cancer: validation and application

BACKGROUND

The Colorectal Cancer Simulated Population model for Incidence and Natural history (CRC-SPIN) is a new microsimulation model for the natural history of colorectal cancer that can be used for comparative effectiveness studies of colorectal cancer screening modalities.

METHODS

CRC-SPIN simulates individual event histories associated with colorectal cancer, based on the adenoma-carcinoma sequence: adenoma initiation and growth, development of preclinical invasive colorectal cancer, development of clinically detectable colorectal cancer, death from colorectal cancer, and death from other causes. We present the CRC-SPIN structure and parameters, data used for model calibration, and model validation. We also provide basic model outputs to further describe CRC-SPIN, including annual transition probabilities between various disease states and dwell times. We conclude with a simple application that predicts the impact of a one-time colonoscopy at age 50 on the incidence of colorectal cancer assuming three different operating characteristics for colonoscopy.

RESULTS

CRC-SPIN provides good prediction of both the calibration and the validation data. Using CRC-SPIN, we predict that a one-time colonoscopy greatly reduces colorectal cancer incidence over the subsequent 35 years.

CONCLUSIONS

CRC-SPIN is a valuable new tool for combining expert opinion with observational and experimental results to predict the comparative effectiveness of alternative colorectal cancer screening modalities.

IMPACT

Microsimulation models such as CRC-SPIN can serve as a bridge between screening and treatment studies and health policy decisions by predicting the comparative effectiveness of different interventions. As such, it is critical to publish model descriptions that provide insight into underlying assumptions along with validation studies showing model performance.

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.

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.

Debate: diminutive polyps noted at CT colonography need not be reported

Colorectal polyps less than 6 mm in size pose a negligible risk to the development of colorectal carcinoma. The sensitivity and specificity for detection of diminutive lesions on all available examinations including CT colonography (CTC) and optical colonoscopy (OC) is relatively low. In the context of regular screening, the low clinical significance and slow to negligible growth of diminutive polyps, as well as the low detection performance of CTC and OC for these lesions, would contribute to wasted health care resource and excess morbidity if each diminutive polyp were referred for potential resection. Respect for patient safety, attention to proper use of resources, and appropriate focus on larger, clinically significant polyps lead the authors to the conclusion that colonic polyps of less than 6 mm should not be separately reported.

Virtual colonoscopy vs optical colonoscopy

IMPORTANCE OF THE FIELD: The high prevalence of colon carcinoma combined with the low compliance of currently recommended screening guidelines explains the continued high mortality rate of colon cancer. Utilizing a strategy of virtual colonoscopy (VC) in asymptomatic patients over 50, with optical colonoscopy (OC) follow-up for removal of detected adenomatous polyps may result in lowering the colon cancer death rate. However, the screening potential of VC has not yet been widely recognized. Debates and doubts of its potential benefits have been frequently seen in the literature since VC was first reported in 1994. AREAS COVERED IN THIS REVIEW: This article reviews the currently available screening options and discuss their advantages and drawbacks. TAKE HOME MESSAGE: VC has many advantages over the existing screening options and its several drawbacks can be mitigated so that it would become a valuable screening modality. A strategy that utilizes VC for population-based screening over the age of 50 and OC for screening high-risk individuals and those with positive VC findings would result in a significantly reduced rate of colon cancer deaths.

Bayesian Calibration of Microsimulation Models

Microsimulation models that describe disease processes synthesize information from multiple sources and can be used to estimate the effects of screening and treatment on cancer incidence and mortality at a population level. These models are characterized by simulation of individual event histories for an idealized population of interest. Microsimulation models are complex and invariably include parameters that are not well informed by existing data. Therefore, a key component of model development is the choice of parameter values. Microsimulation model parameter values are selected to reproduce expected or known results though the process of model calibration. Calibration may be done by perturbing model parameters one at a time or by using a search algorithm. As an alternative, we propose a Bayesian method to calibrate microsimulation models that uses Markov chain Monte Carlo. We show that this approach converges to the target distribution and use a simulation study to demonstrate its finite-sample performance. Although computationally intensive, this approach has several advantages over previously proposed methods, including the use of statistical criteria to select parameter values, simultaneous calibration of multiple parameters to multiple data sources, incorporation of information via prior distributions, description of parameter identifiability, and the ability to obtain interval estimates of model parameters. We develop a microsimulation model for colorectal cancer and use our proposed method to calibrate model parameters. The microsimulation model provides a good fit to the calibration data. We find evidence that some parameters are identified primarily through prior distributions. Our results underscore the need to incorporate multiple sources of variability (i.e., due to calibration data, unknown parameters, and estimated parameters and predicted values) when calibrating and applying microsimulation models.

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.

Variation in polyp detection rates at screening colonoscopy

BACKGROUND

Variation in polyp detection among endoscopists has been used to justify the need for establishing quality standards for colonoscopy performance.

OBJECTIVE

To measure variation in polyp detection rates (PDRs) among endoscopists who perform screening colonoscopy and to identify associated factors.

DESIGN

Cross-sectional analysis of summary-level data.

SETTING

Endoscopy practices in central Indiana.

SUBJECTS

Twenty-five endoscopists and their patients.

MAIN OUTCOME MEASUREMENTS

Mean procedure time (MPT); proportions of patients with any polyp, any adenoma, any polyp > or =1.0 cm, and multiple adenomas; and variation in PDRs and identification of outliers. Multiple linear regression analysis identified factors that accounted for the variation in PDRs.

RESULTS

A total of 2664 screening colonoscopies (1108 women and 1556 men) were performed. The mean patient age was 59 years; the mean proportion of women was 42%; the MPT was 17.1 minutes. Adenoma detection rates ranged from 7% to 44% (P < .001) and from 0% to 13% for large polyps, which was not statistically significant (P = .07). For all polyp categories, only 1 to 3 high outlier endoscopists (ie, higher than mean PDRs) were identified. Models that included the number of procedures, mean age, percentage of women, and MPT accounted for 36% to 56% of the variation in PDRs. In all models, only MPT was significantly associated with PDRs.

LIMITATIONS

Whether each endoscopist's cohort was at comparable risk for colorectal neoplasia was uncertain. In comparison with individual-level data, analysis of summary-level data is limited.

CONCLUSIONS

PDRs vary widely among endoscopists, although only a few (high) outliers were identified. Variation in PDRs was associated only with MPT. Further research is needed to determine the clinical importance of and reasons for this variation.

Successful complete cure en-bloc resection of large nonpedunculated colonic polyps by endoscopic submucosal dissection: a meta-analysis and systematic review

BACKGROUND

Endoscopic submucosal dissection (ESD) has emerged as one of the techniques to successfully resect large colonic polyps en bloc. Complete resection prevents the patient from going through transabdominal colonic resection. We sought to evaluate the proportion of successful en-bloc and complete cure en-bloc resection of large colonic polyps by ESD.

METHODS

Studies that use ESD technique to resect large colonic polyps were selected. Successful en-bloc resection was defined as resection of the polyp in one piece. Successful complete cure en-bloc resection was defined as one piece with histologic disease-free-margin polyp resection. Articles were searched in Medline, PubMed, and Cochrane control trial registry. Pooled proportions were calculated by both fixed and random-effects model.

RESULTS

The initial search identified 2,120 reference articles; 389 relevant articles were selected and reviewed. Data were extracted from 14 studies (n = 1,314) that met the inclusion criteria. The mean +/- standard error size of the polyps was 30.65 +/- 2.88 mm. Pooled proportion of en-bloc resection by the random-effects model was 84.91% (95% confidence interval, 77.82-90.82) and complete cure en-bloc resection was 75.39% (95% confidence interval, 66.69-82.21). The fixed-effects model was not used because of the heterogeneity of studies.

CONCLUSIONS

ESD should be considered the best minimally invasive endoscopic technique in the treatment of large (>2 cm) sessile and flat polyps because it allows full pathological evaluation and cure in most patients. ESD offers an important alternative to surgery in the therapy of large sessile and flat polyps.

CT colonography versus colonoscopy for the detection of advanced neoplasia

BACKGROUND

Advanced neoplasia represents the primary target for colorectal-cancer screening and prevention. We compared the diagnostic yield from parallel computed tomographic colonography (CTC) and optical colonoscopy (OC) screening programs.

METHODS

We compared primary CTC screening in 3120 consecutive adults (mean [+/-SD] age, 57.0+/-7.2 years) with primary OC screening in 3163 consecutive adults (mean age, 58.1+/-7.8 years). The main outcome measures included the detection of advanced neoplasia (advanced adenomas and carcinomas) and the total number of harvested polyps. Referral for polypectomy during OC was offered for all CTC-detected polyps of at least 6 mm in size. Patients with one or two small polyps (6 to 9 mm) also were offered the option of CTC surveillance. During primary OC, nearly all detected polyps were removed, regardless of size, according to established practice guidelines.

RESULTS

During CTC and OC screening, 123 and 121 advanced neoplasms were found, including 14 and 4 invasive cancers, respectively. The referral rate for OC in the primary CTC screening group was 7.9% (246 of 3120 patients). Advanced neoplasia was confirmed in 100 of the 3120 patients in the CTC group (3.2%) and in 107 of the 3163 patients in the OC group (3.4%), not including 158 patients with 193 unresected CTC-detected polyps of 6 to 9 mm who were undergoing surveillance. The total numbers of polyps removed in the CTC and OC groups were 561 and 2434, respectively. There were seven colonic perforations in the OC group and none in the CTC group.

CONCLUSIONS

Primary CTC and OC screening strategies resulted in similar detection rates for advanced neoplasia, although the numbers of polypectomies and complications were considerably smaller in the CTC group. These findings support the use of CTC as a primary screening test before therapeutic OC.

Cost-effectiveness of colorectal cancer screening with computed tomography colonography: the impact of not reporting diminutive lesions

BACKGROUND

Prior cost-effectiveness models analyzing computed tomography colonography (CTC) screening have assumed that patients with diminutive lesions (<or=5 mm) will be referred to optical colonoscopy (OC) for polypectomy. However, consensus guidelines for CTC recommend reporting only polyps measuring >or=6 mm. The purpose of the current study was to assess the potential harms, benefits, and cost-effectiveness of CTC screening without the reporting of diminutive lesions compared with other screening strategies.

METHODS

The cost-effectiveness of screening with CTC (with and without a 6-mm reporting threshold), OC, and flexible sigmoidoscopy (FS) were evaluated using a Markov model applied to a hypothetical cohort of 100,000 persons age 50 years.

RESULTS

The model predicted an overall cost per life-year gained relative to no screening of $4361, $7138, $7407, and $9180, respectively, for CTC with a 6-mm reporting threshold, CTC with no threshold, FS, and OC. The incremental costs associated with reporting diminutive lesions at the time of CTC amounted to $118,440 per additional life-year gained, whereas the incidence of colorectal cancer was reduced by only 1.3% (from 36.5% to 37.8%). Compared with primary OC screening, CTC with a 6-mm threshold resulted in a 77.6% reduction in invasive endoscopic procedures (39,374 compared with 175,911) and 1112 fewer reported OC-related complications from perforation or bleeding.

CONCLUSIONS

CTC with nonreporting of diminutive lesions was found to be the most cost-effective and safest screening option evaluated, thereby providing further support for this approach. Overall, the removal of diminutive lesions appears to carry an unjustified burden of costs and complications relative to the minimal gain in clinical efficacy.

Characteristics of advanced adenomas detected at CT colonographic screening: implications for appropriate polyp size thresholds for polypectomy versus surveillance

OBJECTIVE

Advanced adenomas are the primary target in colorectal screening. The purpose of this study was to delineate the prevalence and imaging characteristics of advanced adenomas detected at screening CT colonography (CTC) and the rates of invasive carcinoma and high-grade dysplasia for various polyp size categories. These observations may be a basis for formulation of polypectomy thresholds and CTC surveillance strategies.

MATERIALS AND METHODS

The imaging and pathologic findings for polyps measuring 6 mm or more obtained from a CTC screening population of 3,536 persons during a 32-month period were retrospectively reviewed. From this group, prevalence, size, histologic features, morphologic features, and location of advanced adenomas were tabulated. Advanced adenomas were defined by size (> or = 10 mm) and/or histologic findings (prominent villous component or high-grade dysplasia).

RESULTS

A total of 123 (38.3%) of 321 adenomas measuring 6 mm or more were classified as advanced, the overall prevalence being 3.1% (111 of 3,536 patients). The mean size of advanced adenomas was 16.6 +/- 11.6 mm; most of the lesions (116/123, 94.3%) qualified as advanced on the basis of the size criterion alone. The seven lesions measuring 6-9 mm constituted 3.4% (7/205) of all medium-sized adenomas. The largest percentage (65/123, 52.8%) of the advanced adenomas had tubular histologic features, followed by tubulovillous (50/123, 40.6%), villous (5/123, 4.1%), and serrated (3/123, 2.4%) histologic features. High-grade dysplasia was uncommon (6/123, 4.9%), typically occurring in large lesions. Seven cases of cancer were detected, all lesions measuring 10 mm or more in size. The majority of advanced adenomas were classified as sessile (57/123, 46.3%) or pedunculated (57/123, 46.3%); a small percentage were flat (9/123, 7.3%). Advanced adenomas were located in the proximal colon in 43.9% (54/123) and distal colon in 56.1% (69/123) of the cases.

CONCLUSION

Advanced adenomas were generally large (> or = 10 mm in size); only a small percentage were medium sized (6-9 mm). There was a very low prevalence of high-grade dysplasia and invasive carcinoma in this series, particularly in the medium-sized group of lesions. These findings lend support to the practice of CTC screening in which large polyp size is used as a surrogate measure for the possible presence of advanced histologic features and medium-sized lesions are followed with noninvasive surveillance protocols.