Comparison of CT colonography, colonoscopy, sigmoidoscopy and faecal occult blood tests for the detection of advanced adenoma in an average risk population

Electronic cleansing for CT colonography: does it help CAD software performance in a high-risk population for colorectal cancer?

OBJECTIVE

To compare the performance of computer-aided detection (CAD) for CT colonography (CTC) with and without electronic cleansing (EC) in a high-risk population tagged with a faecal tagging (FT) protocol.

METHODS

Thirty-two patients underwent CTC followed by same-day colonoscopy. All patients underwent bowel preparation and FT with barium and gastrografin. Each CTC dataset was processed with colon CAD with and without EC. Per-polyp sensitivity was calculated. The average number of false-positive (FP) results and their causes were also analysed and compared.

RESULTS

Eighty-six polyps were detected in 29 patients. Per-polyp sensitivities of CAD with EC (93.8% and 100%) were higher than those without EC (84.4% and 87.5%) for polyps >or=6 mm and >or=10 mm, respectively. However, the differences were not significant. The average number (6.3) of FPs of CAD with EC was significantly larger than that (3.1) without EC. The distribution of FPs in both CAD settings was also significantly different. The most common cause of FPs was the ileocaecal valve in both datasets. However, untagged faeces was a significantly less common cause of FPs with EC, EC-related artefacts being more common.

CONCLUSION

Electronic cleansing has the potential to improve per-polyp sensitivity of CTC CAD, although the significantly larger number of FPs with EC remains to be improved.

CT colonography with decreased purgation: balancing preparation, performance, and patient acceptance

OBJECTIVE

Reduction or elimination of catharsis with fecal tagging enhances the tolerability of CT colonography (CTC) and may increase compliance with colorectal cancer (CRC) screening recommendations. We systematically reviewed studies that prospectively evaluated performance and patient satisfaction with decreased-purgation CTC and with optical colonoscopy.

CONCLUSION

The nine studies reviewed showed moderate-to-good performance for decreased-purgation CTC; however, data are limited, and study design and data presentation are inconsistent. Further study of decreased-purgation CTC and standardization of terminology are needed.

Noninvasive radiologic imaging of the large intestine: a valuable complement to optical colonoscopy

PURPOSE OF REVIEW

Radiologic imaging of the large intestine continues to evolve and expand the potential for noninvasive diagnosis. The aim of this review is to provide an update on current and emerging clinical capabilities for a variety of radiologic diagnostic imaging tools for evaluating the colon and rectum.

RECENT FINDINGS

The utility of computed tomography for the evaluation of symptomatic inflammatory and neoplastic conditions of the colon is well established, but the clinical role of computed tomography colonography is rapidly evolving. In addition to a number of diagnostic indications, computed tomography colonography is emerging as a potential frontline colorectal screening test for cancer prevention. MRI has become increasingly valuable for rectal cancer staging and inflammatory bowel disease but has yet to gain momentum for polyp evaluation. PET imaging has been primarily utilized for oncologic indications, but also holds considerable potential for inflammatory conditions. Other imaging modalities, such as the barium enema, conventional radiography, and ultrasound, play a much more limited role.

SUMMARY

Advances in radiologic imaging of the colorectum will continue to expand the capabilities and clinical indications for noninvasive diagnosis, allowing for a greater emphasis on the complementary roles of tissue sampling and therapy with optical colonoscopy.

Perspectives of colorectal cancer screening in Germany 2009

Adequate screening methods can decrease colorectal cancer (CRC) mortality. The guaiac test for fecal occult-blood (FOBT) is part of the German CRC Screening Program since 1970 and has evidence level Ia. In randomized multicenter-studies FOBT has an average sensitivity of 24% and decreases CRC mortality up to 30%. Immunological tests for human haemoglobin (iFOBT) show better performance characteristics than guaiac FOBT, with augmented sensitivity and specificity. However, the single tests show wide differences in diagnostic performance and iFOBT is not yet covered by insurance companies although it should replace the guaiac test for CRC screening. Visual colonoscopy, which was introduced to the German National Cancer Screening Program in 2002, is the gold standard for the diagnosis of colorectal neoplasia. From 2003 to 2007 more than 2.8 million examinations have been documented in Germany. The prevalence of adenomas is around 20% and of CRC about 0.7% to 1.0% of the screenings. Seventy percent of the carcinomas detected during screening are in an early stage (UICC I and II). Furthermore, screening colonoscopy is a cost saving procedure with a low complication rate (0.25% overall). Insurance companies save 216€ for each screening colonoscopy mainly by prevention of neoplasia due to polypectomy. In Germany, virtual colonography by computed tomography (CT) or magnetic resonance imaging still lacks standardization of the hard and software. In experienced centres the sensitivity for CRC and large polyps of CT colonography is comparable to colonoscopy but in meta-analyses the ranking is lower. New technologies like computer-aided colonoscopies with sheath or double balloon techniques are coming up as well as capsule colonoscopy, which sensitivity for large polyps is about 70%. Advised by his physician, the patient can choose his most acceptable examination method from this whole set of screening tools.

CT colonography screening: ready for prime time?

Every year more than one million new patients are diagnosed with colon cancer worldwide. Although multiple prospective randomized trials and observational studies have demonstrated that mortality from colon cancer can be reduced with screening and removal of adenomatous polyps, compliance with screening guidelines remains low. Recent CT colonography (CTC) trials have shown that CTC is capable of demonstrating adenomatous polyps ≥10 mm (and in most cases ≥6 mm) with sensitivities comparable to those for optical colonoscopy. Based on these results, at least two expert panels have recommended CTC as an option for colorectal cancer screening. Despite these endorsements, the Centers for Medicare and Medicaid Services (CMS) in the United States recently decided to deny coverage of CTC for colorectal cancer screening. This article addresses the reservations raised by CMS and provides a perspective on whether CTC is ready for routine use as a colorectal cancer screening test.

Polyp detection at 3-dimensional endoluminal computed tomography colonography: sensitivity of one-way fly-through at 120 degrees field-of-view angle

PURPOSE

To investigate whether increasing the visual field-of-view (FOV) angle at 3-dimensional (3D) endoluminal computed tomography colonography (CTC) from 90 degrees to 120 degrees allows for single pass fly-through examination of the supine and prone views without sacrificing polyp detection.

METHODS

Primary 3D endoluminal CTC evaluation using a 120 degree FOV was performed by 2 experienced radiologists on 73 patients harboring 104 colonoscopy-proven polyps measuring 6 mm or larger. Unidirectional fly-through evaluation consisted of rectal-to-cecal (retrograde) navigation on the supine display and cecal-to-rectal (antegrade) navigation on the prone display. Electronic fluid subtraction was not used.

RESULTS

All 104 (100%) polyps were detectable with the single-pass 3D evaluation on either the retrograde supine or antegrade prone fly-through, with 86 (82.7%) of 104 polyps seen on both fly-through views. Of the 18 polyps detected on only one of the two 3D endoluminal passes (10 prone, 8 supine), 13 were either submerged under fluid (n = 12) or within a collapsed segment (n = 1); therefore, these were also undetectable on the corresponding 90 degrees bidirectional fly-through. The remaining 5 (4.8%) polyps were located behind a fold, but these polyps were all detectable on the other fly-through in the reverse direction.

CONCLUSIONS

Increasing the visual FOV angle to 120 degrees allows for a decrease in the total number of supine and prone 3D endoluminal fly-through passes from 4 to 2 without negatively impacting overall polyp detection.

MicroRNAs are novel biomarkers of colorectal cancer

BACKGROUND

Recent studies have identified unique small ribonucleic acids called microRNAs (miRNAs) in colonic tumour tissue and blood that may accurately diagnose the presence of colorectal cancer and help predict disease recurrence. This review explores the potential role of these biomarkers.

METHODS

A literature search identified studies describing miRNAs in colorectal cancers. The outcomes of interest included diagnosis, progression and recurrence of disease, and future therapy.

RESULTS

Overexpression and silencing of specific miRNAs are associated with the development and progression of colorectal cancer. Such a role in oncogenesis suggest that miRNAs may be important targets for gene therapies. Differential expression of specific miRNAs in tissues and blood offers the prospect of their use in early detection and screening for colorectal cancer. MiRNAs are implicated in metastasis and cytotoxic drug resistance. Their manipulation has potential in both prevention of recurrence and palliation.

CONCLUSION

The miRNAs expression profile in tissue and blood has potential for their use in the detection, screening and surveillance of colorectal cancer. Furthermore, miRNAs may be targeted by gene therapy to treat colorectal cancer.

[Chemical or immunological tests for the detection of fecal occult blood in colorectal cancer screening?]

Colorectal cancer (CRC) can be prevented by screening programs in the population at average risk (men and women aged between 50 and 74 years) and at high risk (first degree relatives, CRC hereditary syndromes and chronic inflammatory bowel disease). Early CRC (with submucosal invasion) and advanced adenomas (size > or =10mm, with severe dysplasia or >20% villous component) produce intermittent microscopic blood losses that can be detected through chemical and immunological testing for fecal occult blood (C-FOBT and I-FOBT). Among the screening strategies in the population at average risk, annual or biannual fecal occult blood testing is the most widely used due to its non-invasiveness and low cost. Four randomized clinical trials have shown that annual or biannual screening with guaiac-based tests (C-FOBT) reduces overall mortality due to CRC by 16% and CRC incidence by 20% and 17% respectively. However, these tests have major drawbacks, especially their low sensitivity in detecting early CRC and advanced adenoma, their lack of specificity in detecting human hemoglobin (Hb), and their high fecal Hb detection threshold (>300microgHb/gfeces). In the last few years, major developments have occurred in immunological tests (I-FOBT), based on an antigen-antibody reaction that specifically detects human Hb, and these tests are currently available as an alternative to C-FOBT. Their main advantages are as follows: firstly, I-FOBT specifically detect human Hb in stools and at much lower levels (40-300microgHb/gfeces) than C-FOBT; secondly, automated analysis avoids subjectivity in reading qualitative tests and allows large population groups to be studied in a short time, making I-FOBT ideal for population-based screening; thirdly, I-FOBT fairly accurately selects individuals for colonoscopy so that approximately half of patients with an I-FOBT test show clinically significant colorectal neoplasia (advanced adenoma or invasive CRC); fourthly, the cut-off point for fecal Hb detection can be modified, depending on the availability of endoscopic resources; fifthly, when cut-off points for fecal Hb of 50-150microgHb/gfeces are used, more than twice the number of CRC and advanced adenomas are detected than with C-FOBT, with a reasonable false-positive rate; and sixthly, I-FOBT are better accepted by the population due to their simplicity and ease of use, increasing participation in screening programs. For all these reasons, the current recommendation is that the new quantitative I-FOBT tests replace C-FOBT tests when the strategy of population-based screening through annual or biannual fecal occult blood testing is considered.

In defense of body CT

OBJECTIVE

Rapid technical developments and an expanding list of applications that have supplanted less accurate or more invasive diagnostic tests have led to a dramatic increase in the use of body CT in medical practice since its introduction in 1975. Our purpose here is to discuss medical justification of the small potential risk associated with the ionizing radiation used in CT and to provide perspectives on practice-specific decisions that can maximize overall patient benefit. In addition, we review available dose management and optimization techniques.

CONCLUSION

Dose reduction strategies described in this article must be well understood and properly used, but also require broad-based practice strategies that extend beyond the CT scanner console and default, generic manufacturer settings. In the final analysis, physicians must request the imaging examination that best addresses the specific medical question without allowing worries about radiation to dissuade them or their patients from obtaining needed CT examinations. Ongoing efforts to ensure that CT examinations are both medically justified and optimally performed must continue, and education must be provided to the medical community and general public that put both the potential risks--and benefits--of CT examinations into proper perspective.

CT colonography to screen for colorectal cancer and aortic aneurysm in the Medicare population: cost-effectiveness analysis

OBJECTIVE

CT colonography (CTC) is a recommended test for colorectal cancer (CRC) screening according to the updated 2008 American Cancer Society guidelines. CTC can also accurately detect abdominal aortic aneurysm (AAA). This collaborative gastroenterology-radiology project evaluated the cost-effectiveness and clinical efficacy of CTC in the Medicare population.

MATERIALS AND METHODS

A computerized Markov model simulated the development of CRC and AAA in a hypothetical cohort of 100,000 U.S. adults > or = 65 years old. Screening with CTC at 5- and 10-year intervals using a 6-mm size threshold for polypectomy was compared with primary optical colonoscopy screening every 10 years and with no screening. Base case costs for CTC and optical colonoscopy were $674 and $795, respectively. The costs of the imaging workup for extracolonic findings at CTC were also included.

RESULTS

CTC resulted in 7,786 and 7,027 life-years gained at 5- and 10-year intervals, respectively, compared with 6,032 life-years gained with 10-year optical colonoscopy. The increase in overall efficacy with CTC was primarily due to prevention of AAA rupture because CRC prevention and CRC detection rates were similar for CTC and optical colonoscopy. All three strategies were highly cost-effective compared with no screening, with an incremental cost-effectiveness ratio (ICER) of $6,088, $1,251, and $1,104 per life-year gained for 5-year CTC, 10-year CTC, and 10-year optical colonoscopy strategies, respectively. The ICER of 5-year CTC and 10-year CTC versus optical colonoscopy was $23,234 and $2,144 per life-year gained, respectively.

CONCLUSION

Because of its ability to simultaneously screen for both CRC and AAA, CTC is a highly cost-effective and clinically efficacious screening strategy for the Medicare population.

Colon cancer and the elderly: from screening to treatment in management of GI disease in the elderly

Colorectal cancer is one of the commonest tumours in the Westernized world affecting mainly the elderly. This neoplasm in older individuals occurs more often in the right colon and grows more rapidly than in the young, often shows a mucinous histology and mismatch repair gene changes. Effective screening permits discovery of colorectal cancer at an early highly treatable stage and allows for detection and removal of premalignant colorectal adenomas. Screening methods that focus on cancer detection use fecal assays for the presence of blood or altered DNA, those for detection of adenomas (and early cancer) use endoscopic or computerised radiologic techniques. Broad use of screening methods has lowered colorectal cancer development by about 50%. In addition, prevention of the earliest stage of colon carcinogenesis has been shown to be effective in small prospective studies and epidemiologic surveys but have not been employed in the general population. Since 1996 the chemotherapeutic armamentarium for metastatic colorectal cancer has grown beyond 5-fluorouracil to include an oral 5-fluorouracil prodrug, capecitabine as well as irinotecan and oxaliplatin. Three targeted monoclonal antibodies (Moabs), bevacizumab (an anti-vascular endothelial growth factor Moab) and cetuximab/panitumumab, both anti-epidermal growth factor receptor inhibitors, have also earned regulatory approval. Most stage IV patients are treated with all of these drugs over 2 or 3 sequential lines of palliative chemotherapy and attain median survivals approaching 24 months. Lastly, adjuvant oxaliplatin plus 5-fluorouracil for high risk resected stage II and stage III colon cancer patient has led to substantial improvement in cure rates. With appropriate care of age associated comorbidities these treatment modalities are feasible and effective in the geriatric population.