CT colonography for colon cancer screening

Computed tomography colonography for the practicing radiologist: A review of current recommendations on methodology and clinical indications

Colorectal cancer (CRC) represents one of the most relevant causes of morbidity and mortality in Western societies. CRC screening is actually based on faecal occult blood testing, and optical colonoscopy still remains the gold standard screening test for cancer detection. However, computed tomography colonography (CT colonography) constitutes a reliable, minimally-invasive method to rapidly and effectively evaluate the entire colon for clinically relevant lesions. Furthermore, even if the benefits of its employment in CRC mass screening have not fully established yet, CT colonography may represent a reasonable alternative screening test in patients who cannot undergo or refuse colonoscopy. Therefore, the purpose of our review is to illustrate the most updated recommendations on methodology and the current clinical indications of CT colonography, according to the data of the existing relevant literature.

Preoperative colonoscopy through the colonic stent in patients with colorectal cancer obstruction

AIM: To evaluate the feasibility of a preoperative colonoscopy through a self-expendable metallic stent (SEMS) and to identify the factors that affect complete colonoscopy.

METHODS: A total of 48 patients who had SEMS placement because of acute malignant colonic obstruction underwent preoperative colonoscopy. After effective SEMS placement, patients who showed complete resolution of radiological findings and clinical signs of acute colon obstruction underwent a standard bowel preparation. Preoperative colonoscopy was then performed using a standard colonoscope. If the passage of colonoscope was not feasible gastroscope was used. After colonoscopy, cecal intubation time, grade of bowel preparation, tumor location, stent location, presence of synchronous polyps or cancer, damage to colonoscopy and bleeding, and stent migration after colonoscopy were recorded.

RESULTS: Complete evaluation with colonoscope was possible in 30 patients (62.5%). In this group, adenoma was detected in 13 patients (43.3%). The factors that affected complete colonoscopy were also analyzed: Tumor location at an angle; stent placement at an angle; and stent expansion diameter, which affected complete colonoscopy significantly. However in multivariate analysis, stent expansion diameter was the only significant factor that affected complete colonoscopy. Complete evaluation using additional gastroscope was feasible in 42 patients (87.5%).

CONCLUSION: Preoperative colonoscopy through the colonic stent using only conventional colonoscope was unfavorable. The narrow expansion diameter of the stent may predict unfavorable outcome. In such a case, using small caliber scope should be considered and may expect successful outcome.

Colorectal laterally spreading tumors by computed tomographic colonography

To date, few reports focused primarily on detecting colorectal laterally spreading tumors (LSTs) have been published. The aim of this study was to determine the visibility of LSTs on computed tomographic colonography (CTC) compared with that on colonoscopy as a standard. We retrospectively reviewed and matched data on endoscopic and CTC reports in 157 patients (161 LSTs) who received a multidetector CT scan using contrast media immediately after total colonoscopy at the National Cancer Center Hospital in Tokyo, Japan, between December 2005 and August 2010. The results of the total colonoscopy were known at the time of the CTC procedure and reading. Of the 161 LSTs detected on colonoscopy, 138 were observed and matched by CTC (86%). Of the 91 granular type LSTs (LST-Gs), 88 (97%) were observed and matched, while of the 70 non-granular type LSTs (LST-NGs), 50 (71%) were observed and matched by CTC (p < 0.0001). CTC enabled observation of 73% (22/30) of 20–29 mm, 83% (35/42) of 30–39 mm, 88% (49/56) of 40–59 mm, and 97% (32/33) of ≥60 mm tumors. The rate of observed LSTs by CTC was 86% (97% of LST-G, 71% of LST-NG) of the LSTs found during total colonoscopy.

Preoperative colonoscopy for detection of synchronous neoplasms after insertion of self-expandable metal stents in occlusive colorectal cancer: comparison of covered and uncovered stents

Background/Aims

In patients with occlusive colorectal cancers, a complete preoperative evaluation of the colon proximal to the obstruction is often impossible. We aimed to evaluate the feasibility of preoperative colonoscopy after stent placement and to determine whether the success rate of colonoscopy differs between covered and uncovered stents.

Methods

Seventy-three patients with malignant colorectal obstruction were enrolled prospectively. In patients with a resectable cancer, a preoperative colonoscopy was performed after insertion of a self-expandable metal stent (SEMS). The success rate of complete preoperative colonoscopy was compared between covered and uncovered stents.

Results

Forty-five of 73 patients who underwent stent placement had a resectable cancer (61.6%). A complete preoperative colonoscopy was possible in 40 of 45 patients (88.9%). The success rate of complete preoperative colonoscopy was significantly lower in the covered-stent group when the obstructing mass lesion was located in the sigmoid colon (p=0.024). Synchronous cancer was detected in one patient (2.2%). Stent migration was observed in four patients with a covered stent.

Conclusions

A preoperative complete colonoscopy after SEMS placement was feasible and safe in most patients with malignant colorectal obstruction. Uncovered stents seem to have more advantages than covered stents in preoperative colonoscopy proximal to the obstruction.

[Role of patient safety in the official approval of new surgical techniques and devices]

Health technological industry brings every year thousands of new devices to the market worldwide. However, there is a large gap between the process of device approval and the control after release. Although, drugs can be used in health care only if they underwent randomized placebo controlled trials there are only a few devices that had similar studies. Surgery is a dangerous part of medicine and new technologies can represent hazard for patient safety.

Patients with polyps larger than 5 mm in computed tomography colonoscopy screening have high risk for advanced colonic neoplasia in Asia

BACKGROUND & AIMS

Computed tomography colonography (CTC) is a recommended screening modality for colorectal cancer (CRC). It is not known whether polyps 6-9 mm based on CRC are likely to have advanced histologic features in Asian patients. We estimated the risk of advanced colonic neoplasia (ACN) from polyps <10 mm and the risk of ACN detection failure if patients with polyps <10 mm are not referred for colonoscopy.

METHODS

The study included 1457 subjects from the Asia-Pacific Working Group on CRC screening and the Hong Kong CRC screening program. Polyps and ACN found during colonoscopy examinations were classified by size and histology.

RESULTS

Of the subjects, 38.2% had polyps; 16.7% of these were ACN, 5.4% of ACN were ≤5 mm, and 24.7% of the ACN were 6-9 mm. Adopting the policy of reporting polyps found by CTC of <5 mm as normal and repeating CTC in patients with polyps of 6-9 mm, 5.4% of subjects with ACN, 4.5% of male subjects, and 11.5% of subjects with family history of CRC would be classified as normal. In referring patients with polyps of 6-9 mm for CTC surveillance, 20.4% of those with ACN, 22.4% of those that are male, and 23.1% of those with family histories of CRC would have polypectomies delayed by at least 3 years.

CONCLUSIONS

A substantial proportion of polyps <10 mm have advanced histologic features in Asia, so patients with a polyp of 6 mm or more at CTC should be offered colonoscopies with polypectomies, rather than CTC surveillance of polyps.

Computed tomographic colonography: Hope or hype?

Computed tomographic colonography (CTC) is a promising emerging technology for imaging of the colon. This concise review discusses the currently available data on CTC technique, test characteristics, acceptance, safety, cost-effectiveness, follow-up strategy, and extracolonic findings. In summary, CTC technique is still evolving, and further research is needed to clarify the role of automated colonic insufflation, smooth-muscle relaxants, intravenous and oral contrast, software rendering, and patient positioning. Currently, full bowel preparation is still required to achieve optimal results. The sensitivity for detecting large polyps (> 1 cm) can be as high as 85%, with specificity of up to 97%. These test characteristics are almost comparable to those of conventional colonoscopy. Patient acceptance of CTC is generally higher than that for colonoscopy, especially in patients who have never undergone either procedure. CTC is generally safe, although uncommon instances of colonic perforation have been documented. In terms of cost-effectiveness, most decision analyses have concluded that CTC would only be cost-effective if it were considerably cheaper than conventional colonoscopy. The proper follow-up strategy for small polyps or incidental extracolonic findings discovered during CTC is still under debate. At present, the exact clinical role of virtual colonoscopy still awaits determination. Even though widespread CTC screening is not available today, in the future there may eventually be a role for this technology. Technological advances in this area will undoubtedly continue, with multi-detector row CT scanners allowing thinner collimation and higher resolution images. Stool-tagging techniques are likely to evolve and may eventually allow for low-preparation CTC. Perceptual and fatigue-related reading errors can potentially be minimized with the help of computer-aided detection software. Further research will define the exact role of this promising technology in our diagnostic armamentarium.

Polyp size and advanced histology in patients undergoing colonoscopy screening: implications for CT colonography

BACKGROUND & AIMS

Colorectal cancer screening with diagnostic imaging can detect polyps. The management of patients whose largest polyp is less than 10 mm is uncertain. The primary aim of this study was to determine rates of advanced histology in patients undergoing colorectal cancer screening whose largest polyp is 9 mm or less.

METHODS

Subjects include all asymptomatic adults receiving colonoscopy for screening during 2005 from 17 practice sites, which provide both colonoscopy and pathology reports to the Clinical Outcomes Research Initiative repository. Patients were classified by size of largest polyp. Advanced histology was defined as an adenoma with villous or serrated histology, high-grade dysplasia, or an invasive cancer. Risk factors for advanced histology were determined using Pearson chi(2) and Fisher exact tests.

RESULTS

Among 13,992 asymptomatic patients who had screening colonoscopy, 6360 patients (45%) had polyps, with complete histology available in 5977 (94%) patients. The proportion with advanced histology was 1.7% in the 1- to 5-mm group, 6.6% in the 6- to 9-mm group, 30.6% in the greater than 10-mm group, and 72.1% in the tumor group. Distal location was associated with advanced histology in the 6- to 9-mm group (P = .04) and in the greater than 10-mm group (P = .002).

CONCLUSIONS

One in 15 asymptomatic patients whose largest polyp is 6 to 9 mm will have advanced histology and would undergo surveillance at 3 years based on current guidelines. Because histology is necessary for this decision, most of these patients should be offered colonoscopy. Further study should determine whether patients whose largest polyp is 1-5 mm can be safely followed without polypectomy.

The efficacy of intravenous contrast-enhanced 16-raw multidetector CT colonography for detecting patients with colorectal polyps in an asymptomatic population in Korea

PURPOSE

The purpose of this study is to compare the sensitivity of computed tomography (CT) colonography (CTC) with that of colonoscopy for detecting patients with colorectal polyps in an asymptomatic screening population in Korea, thus to evaluate a possibility, whether CTC could be used as a screening tool for colorectal polyps.

METHODS

A total of 241 asymptomatic adults underwent intravenous contrast-enhanced CTC and colonoscopy successively on the same day. Bowel preparation was performed by 4 L of polyethylene glycol (n=172) or 90 mL of sodium phosphate (n=69). The CTC findings were released to the colonoscopists after the first examination of each segment, a procedure known as segmental unblinded colonoscopy, and were used as the reference standard. The diagnostic performance of CTC for colorectal polyps was calculated.

RESULTS

The per-patient sensitivities of CTC were 68.5% (37/54) and 86.7% (13/15) for polyp > or = 6 and > or = 10 mm, inferior to those of colonoscopy, 92.6% (50/54) and 100% (15/15), respectively. The per-polyp sensitivities of CTC were 60.4% (61/101) and 72.7% (16/22) for polyp > or = 6 and > or = 10 mm, respectively. The low sensitivity of CTC was related with flat morphology. CTC detected only 37.5% (9/24) of flat polyps > or = 6 mm. Bowel preparation by sodium phosphate further decreased the positive predictive value and specificity than by polyethylene glycol.

CONCLUSIONS

Screening by CTC with asymptomatic population was not promising in Korea despite using advanced CT technology (16-row detector). Bowel preparation was one of the key determinants of the specificity of CTC.

Not your father's colonoscopy: a high-tech future for screening and surveillance of colorectal cancer

The 20-year technology slump in endoscopic innovation is finally giving way to a flurry of technologies, of which many are directed specifically at improving or even replacing traditional colonoscopy. These technologies include "smart" overtubes, electronically mapped and driven instruments, and completely self-propelled devices. In addition to nonendoscopic technologies such as CT, these innovations may dramatically alter the practice of colorectal cancer screening, the "bread and butter" of gastroenterologists in this country. There are multiple and complex forces driving these changes, including a mismatch between the supply and demand in colonoscopy, patient convenience and comfort, costs, and more recently, a growing concern about the miss rate of conventional colonoscopy.

Advanced endoscopic technologies

The use of endoscopy for diagnosing and treating ailments of the alimentary tract has evolved steadily over the past few decades, with tremendous growth and innovation in the past few years. Initially, endoscopy relied on rigid telescopes, direct visualization, and dangerously exothermic sources of illumination. The introduction of fiber optics, charge-coupled-device cameras, and increasingly efficient light sources has enabled researchers to investigate areas of the human gastrointestinal tract through flexible endoscopy not previously thought to be reachable without formal surgical exploration. The more recent advances in scope platforms, devices, and techniques have allowed researchers to push the envelope of endoscopic diagnostics and therapeutics to greater heights. Specific new platforms include ColonoSight and mother-daughter endoscopes such as the ShapeLock TransPort and the SpyGlass direct visualization system. Specific devices include the EndoCinch suturing system, the full-thickness Plicator procedure, Esophyx, the Stretta system, and the HALO(360) system. Specific new techniques include small-caliber endoscopy, endoscopic mucosal and submucosal resection, and natural orifice translumenal endoscopic surgery (NOTES). This article describes the most relevant recent advances in endoscopic innovation with regard to platform design, devices, and techniques anticipated to serve as the foundation for further research and design for developing generations of endoscopic technologies to come.

The utility of flexible sigmoidoscopy after a computerized tomographic colonography revealing only rectosigmoid lesions

BACKGROUND

Identifying polyps by computerized tomographic colonography typically prompts colonoscopy, increasing its cost, risk and inconvenience. Many polyps are confined to the rectosigmoid and theoretically amenable to resection via flexible sigmoidoscopy.

AIM

To determine the prevalence of advanced proximal colonic neoplasia when computerized tomographic colonography reveals only rectosigmoid polyps, and characterize the yield of polypectomy via flexible sigmoidoscopy in such patients.

METHODS

Subjects underwent computerized tomographic colonography and colonoscopy with segmental unblinding. Patients with only rectosigmoid findings by computerized tomographic colonography were identified retrospectively. Flexible sigmoidoscopy findings were estimated by including lesions distal to the descending/sigmoid colon junction during colonoscopy. Proximal lesions were also reviewed. Advanced lesions were defined as: adenocarcinoma, tubular adenoma >1 cm, > or =3 tubular adenomas, tubulovillous histology or high-grade dysplasia.

RESULTS

By computerized tomographic colonography, 15% (203 of 1372) had only rectosigmoid polyps. Concomitant lesions in the proximal colon were seen in 32% (64 of 203) during colonoscopy. Advanced proximal neoplasia occurred in 2% (three of 203) with only rectosigmoid polyps on computerized tomographic colonography.

CONCLUSIONS

Using flexible sigmoidoscopy to follow-up computerized tomographic colonography demonstrating only rectosigmoid polyps would eliminate 15% of subsequent colonoscopies. This strategy carries a small risk of missed proximal advanced neoplasia. This miss rate appears comparable to that of colonoscopy alone. Further study on the cost-effectiveness of this approach is warranted.

Who is responsible for evaluating the safety and effectiveness of medical devices? The role of independent technology assessment

INTRODUCTION

The global medical technology industry brings thousands of devices to market every year. However, significant gaps persist in the scientific literature, in the medical device approval process, and in the realm of postmarketing surveillance. Although thousands of drugs obtain approval only after review in randomized controlled trials, relatively few new medical devices are subject to comparable scrutiny.

OBJECTIVE

To improve health outcomes, we must enhance our scrutiny of medical devices, and, without simply deferring to the Food and Drug Administration, we must ask ourselves: Who is responsible for evaluating the safety and effectiveness of medical devices?

CONCLUSIONS

Technology assessments by independent organizations are a part of the solution to this challenge and may motivate further research focused on patient outcomes.

Laparoscopic resection of curable colon and rectal cancer: an evidence-based review

The initial enthusiastic application of laparoscopic techniques to colorectal surgical procedures was tempered in the early 1990s by reports of tumor implants in the laparoscopic incisions. Substantial evidence has accumulated, including evidence from randomized controlled trials, to support that laparoscopic resection results in oncologic outcomes similar to open resection, when performed by well-trained, experienced surgeons. This review was developed in conjunction with guidelines published by the Society of American Gastrointestinal and Endoscopic Surgeons. Data from the surgical literature concerning laparoscopic resection of curable colorectal cancer was evaluated regarding diagnostic evaluation, preoperative preparation, operative techniques, prevention of tumor implants, and training and experience. Recommendations are accompanied by an assessment of the level of supporting evidence available at the time of the development of the guidelines.

Update on Colorectal Cancer Imaging

Colorectal cancer remains a leading cancer killer worldwide. The disease is both curable and preventable, and yet the importance of widespread screening is only now starting to be appreciated. This article reviews the variety of diagnostic tests, imaging procedures and endoscopic examinations available to detect colorectal cancer and polyps in their early stage and also presents details on various screening options. The critical role of the radiologist is elaborated on including accurate assessment of the tumor extent within the bowel wall and beyond and the detection of lymph node and distant metastases. Staging with CT, MR imaging, endorectal ultrasound, and positron emission tomography are of paramount importance in determining the most appropriate therapy and the risk of tumor recurrence and overall prognosis.

A novel retrograde-viewing auxiliary imaging device (Third Eye Retroscope) improves the detection of simulated polyps in anatomic models of the colon

BACKGROUND

Colonoscopy is the "gold standard" for colorectal polyp and cancer detection, but important lesions may be missed on the proximal aspect of haustral folds, rectal valves, or flexures.

OBJECTIVE

Our purpose was to evaluate a prototype auxiliary imaging device that extends beyond the colonoscope's tip, providing a continuous retrograde view to detect lesions missed by the forward-viewing colonoscope.

DESIGN

Three anatomic models of the colon were prepared with simulated polyps, 32% in obvious locations and 68% on the proximal aspect of folds. Six endoscopists examined each model with two methods. Method A used a standard video colonoscope. Method B involved an identical colonoscope with a retrograde-viewing auxiliary device positioned within its instrument channel. Order of testing was randomized and blinded.

SETTING

Laboratory bench.

MAIN OUTCOME MEASUREMENTS

Detection rates for simulated polyps.

RESULTS

Of 78 "obvious" polyps, 69 (88%) and 70 (90%) were detected by methods A and B, respectively (P > .9). In contrast, of 162 polyps on proximal aspects of folds, 20 (12%) and 131 (81%) were detected by methods A and B, respectively (P < .00001).

LIMITATIONS

Limitations resulted from (1) use of commercially available anatomic models in which haustral folds are less prominent and more rigid than in humans and (2) evaluation of a prototype device that had larger size and narrower angle of view than the planned production model and that was fixed in relation to the colonoscope.

CONCLUSIONS

In simulated testing, a retrograde-viewing auxiliary imaging device used with a standard video colonoscope significantly improves detection rates of simulated polyps and promises to enhance the diagnostic yield of colonoscopy in humans.