Does CT colonography have a role for population-based colorectal cancer screening?

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.

The potential of imaging techniques as a screening tool for colorectal cancer: a cost-effectiveness analysis

OBJECTIVE

Imaging may be promising for colorectal cancer (CRC) screening, since it has test characteristics comparable with colonoscopy but is less invasive. We aimed to assess the potential of CT colonography (CTC) and MR colonography (MRC) in terms of (cost-effectiveness) using the Adenoma and Serrated pathway to Colorectal CAncer model.

METHODS

We compared several CTC and MRC strategies with 5- or 10-yearly screening intervals with no screening, 10-yearly colonoscopy screening and biennial faecal immunochemical test (FIT) screening. We assumed trial-based participation rates in the base-case analyses and varied the rates in sensitivity analyses. Incremental lifetime costs and health effects were estimated from a healthcare perspective.

RESULTS

The health gain of CTC and MRC was similar and ranged from 0.031 to 0.048 life-year gained compared with no screening, for 2-5 screening rounds. Lifetime costs per person for MRC strategies were €60-110 higher than those for CTC strategies with an equal number of screening rounds. All imaging-based strategies were cost-effective compared with no screening. FIT screening was the dominant screening strategy, leading to most LYG and highest cost-savings. Compared with three rounds of colonoscopy screening, CTC with five rounds was found to be cost-effective in an incremental analysis of imaging strategies. Assumptions on screening participation have a major influence on the ordering of strategies in terms of costs and effects.

CONCLUSION

CTC and MRC have potential for CRC screening, compared with no screening and compared with three rounds of 10-yearly colonoscopy screening. When taking FIT screening as the reference, imaging is not cost-effective. Participation is an important driver of effectiveness and cost estimates.

ADVANCES IN KNOWLEDGE

This is the first study to assess the cost-effectiveness of MRC screening for CRC.

Methylation pattern of ALX4 gene promoter as a potential biomarker for blood-based early detection of colorectal cancer

BACKGROUND

To develop a non-invasive screening method for colorectal cancer, we evaluated the methylation of ALX4 gene promoter in serum samples from patients with colorectal cancer (CRC) and equal number of healthy individuals.

MATERIALS AND METHODS

In serum samples from 25 patients with colorectal cancer and 25 healthy control subjects, isolated serum free-floating DNA was treated with sodium bisulfite and analyzed by methylation-specific polymerase chain reaction (MSP) with primers specific for methylated or unmethylated promoter CpG island sequences of the ALX4 gene.

RESULTS

Methylation of the ALX4 gene promoter was present in the serum DNA of patients with adenoma and colorectal cancer. A sensitivity of 68% and specificity of 88% were achieved in the detection of promoter methylation in colorectal neoplasia samples. The difference in methylation status of the ALX4 promoter between the patients with colorectal neoplasia and the control group was statistically highly significant (P < 0.001).

CONCLUSIONS

The results indicate that this serum free DNA test of methylation of the ALX4 gene promoter is a sensitive and specific method. Therefore in combination with other useful markers it seems ALX4 has the potential of a clinically useful test for the early detection of colorectal cancer.

Computed tomographic colonography is valuable for post-treatment evaluation and screening of hidden colorectal cancer in patients with cryptogenic pyogenic liver abscess

BACKGROUND/AIMS

It has been demonstrated that cryptogenic pyogenic liver abscess (PLA) is associated with colonic mucosal defect, especially colorectal cancer (CRC). Therefore, the screening of CRC in patients with cryptogenic PLA is important. This study was to investigate whether computed tomographic colonography (CTC) has value as a follow-up modality as well as CRC screening tool in patients with PLA.

METHODS

A retrospective evaluation of 109 patients with cryptogenic PLA who underwent CTC or colonoscopy for CRC screening between July 2005 and July 2012 was performed. The patients were divided into a CTC group (n = 68) and colonoscopy group (n = 41) after treatment of liver abscess, and compared concerning the detection rate of advanced neoplasia, consisting of advanced adenomas and invasive carcinomas. Patients with advanced polyps in CTC surveillance underwent subsequent colonoscopy.

RESULTS

Advanced colonic neoplasia was detected in 9 of the 68 patients (13.2%) in the CTC group and 8 of the 41 patients (19.5%) in the conventional colonoscopy group (p = 0.42). The treatment response of all abscess lesions was clearly visualized on CTC, with complete resolution in 17.6% (12/68) of patients. After adjustment for sex and pathogens, old age (≥65 years) was significantly associated with advanced neoplasia (OR 5.481; 95% CI 1.757-17.100; p = 0.03).

CONCLUSION

CTC has a valuable dual role as a follow-up modality and in the screening of CRC in patients with cryptogenic PLA, particularly in elderly patients over 65 years of age.

CT colonography: accuracy, acceptance, safety and position in organised population screening

Colorectal cancer (CRC) is the second most common cancer and second most common cause of cancer-related deaths in Europe. The introduction of CRC screening programmes using stool tests and flexible sigmoidoscopy, have been shown to reduce CRC-related mortality substantially. In several European countries, population-based CRC screening programmes are ongoing or being rolled out. Stool tests like faecal occult blood testing are non-invasive and simple to perform, but are primarily designed to detect early invasive cancer. More invasive tests like colonoscopy and CT colonography (CTC) aim at accurately detecting both CRC and cancer precursors, thus providing for cancer prevention. This review focuses on the accuracy, acceptance and safety of CTC as a CRC screening technique and on the current position of CTC in organised population screening. Based on the detection characteristics and acceptability of CTC screening, it might be a viable screening test. The potential disadvantage of radiation exposure is probably overemphasised, especially with newer technology. At this time-point, it is not entirely clear whether the detection of extracolonic findings at CTC is of net benefit and is cost effective, but with responsible handling, this may be the case. Future efforts will seek to further improve the technique, refine appropriate diagnostic algorithms and study cost-effectiveness.

Magnetic resonance colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy: patient burden and preferences

OBJECTIVES

To evaluate patient burden and preferences for MR colonography with a limited bowel preparation and automated carbon dioxide insufflation in comparison to conventional colonoscopy.

METHODS

Symptomatic patients were consecutively recruited to undergo MR colonography with automated carbon dioxide insufflation and a limited bowel preparation followed within four weeks by colonoscopy with a standard bowel cleansing preparation. Four questionnaires regarding burden (on a five-point scale) and preferences (on a seven-point scale) were addressed after MR colonography and colonoscopy and five weeks after colonoscopy.

RESULTS

Ninety-nine patients (47 men, 52 women; mean age 62.3, SD 8.7) were included. None of the patients experienced severe or extreme burden from the MR colonography bowel preparation compared to 31.5% of the patients for the colonoscopy bowel preparation. Colonoscopy was rated more burdensome (25.6% severe or extreme burden) compared to MR colonography (5.2% severe or extreme burden) (P<0.0001). When discarding the bowel preparations, the examinations were rated equally burdensome (P=0.35). The majority of patients (61.4%) preferred MR colonography compared to colonoscopy (29.5%) immediately after the examinations and five weeks later (57.0% versus 39.5%).

CONCLUSION

MR colonography with a limited bowel preparation and automated carbon dioxide insufflation demonstrated less burden compared to colonoscopy. The majority of patients preferred MR colonography over colonoscopy.

Evaluation of dose reduction and image quality in CT colonography: comparison of low-dose CT with iterative reconstruction and routine-dose CT with filtered back projection

OBJECTIVE

To prospectively evaluate the radiation dose and image quality comparing low-dose CT colonography (CTC) reconstructed using different levels of iterative reconstruction techniques with routine-dose CTC reconstructed with filtered back projection.

METHODS

Following institutional ethics clearance and informed consent procedures, 210 patients underwent screening CTC using automatic tube current modulation for dual positions. Examinations were performed in the supine position with a routine-dose protocol and in the prone position, randomly applying four different low-dose protocols. Supine images were reconstructed with filtered back projection and prone images with iterative reconstruction. Two blinded observers assessed the image quality of endoluminal images. Image noise was quantitatively assessed by region-of-interest measurements.

RESULTS

The mean effective dose in the supine series was 1.88 mSv using routine-dose CTC, compared to 0.92, 0.69, 0.57, and 0.46 mSv at four different low doses in the prone series (p < 0.01). Overall image quality and noise of low-dose CTC with iterative reconstruction were significantly improved compared to routine-dose CTC using filtered back projection. The lowest dose group had image quality comparable to routine-dose images.

CONCLUSIONS

Low-dose CTC with iterative reconstruction reduces the radiation dose by 48.5 to 75.1% without image quality degradation compared to routine-dose CTC with filtered back projection.

KEY POINTS

• Low-dose CTC reduces radiation dose ≥ 48.5% compared to routine-dose CTC. • Iterative reconstruction improves overall CTC image quality compared with FBP. • Iterative reconstruction reduces overall CTC image noise compared with FBP. • Automated exposure control with iterative reconstruction is useful for low-dose CTC.

[Optical colonoscopy and virtual colonoscopy: the current role of each technique]

The importance of optical or conventional colonoscopy in diagnosing colon disease is undisputed. In this context, optical colonoscopy is the gold standard against which other techniques must be validated. Apart from enabling direct inspection of the colonic mucosa, optical colonoscopy enables biopsies and techniques to treat and prevent colorectal cancer. Virtual colonoscopy or CT colonography has been validated in multicenter studies; virtual colonoscopy is as sensitive as optical colonoscopy for the detection of polyps and colon cancer. It is currently the only valid alternative to optical colonoscopy. Its role in patients with medium or high risk of colon cancer is in the process of being defined as multidisciplinary teams gain experience. This article aims to discuss the usefulness of virtual colonoscopy in different clinical situations, emphasizing the situations in which there is enough scientific evidence, and to discuss the controversies surrounding its possible use for population-based screening.

Ethical issues in colorectal cancer screening

In many countries, colorectal cancer screening is currently an established population screening program due to the evidence on its reduction of colorectal cancer mortality. There is general consensus that colorectal cancer screening meets the screening criteria as proposed by Wilson and Jungner. However, as for all population screening programs, colorectal cancer screening also has disadvantages and thereby entails ethical issues. There are the general issues concerning the introduction of screening programs (e.g. medicalization, overdiagnosis and overtreatment, information provision to screenees), evaluation of cancer screening programs (e.g. lead time and length bias), chosen screening method (e.g. false-positive and false-negative test results, reduction of all-cause mortality, choice between different screening methods). The different colorectal cancer screening methods and the ethical issues concerning colorectal cancer screening will be discussed in this review.

An international review of the main cost-effectiveness drivers of virtual colonography versus conventional colonoscopy for colorectal cancer screening: is the tide changing due to adherence?

OBJECTIVES

The majority of recent cost-effectiveness reviews concluded that computerised tomographic colonography (CTC) is not a cost-effective colorectal cancer (CRC) screening strategy yet. The objective of this review is to examine cost-effectiveness of CTC versus optical colonoscopy (COL) for CRC screening and identify the main drivers influencing cost-effectiveness due to the emergence of new research.

METHODS

A systematic review was conducted for cost-effectiveness studies comparing CTC and COL as a screening tool and providing outcomes in life-years saved, published between January 2006 and November 2012.

RESULTS

Nine studies were included in the review. There was considerable heterogeneity in modelling complexity and methodology. Different model assumptions and inputs had large effects on resulting cost-effectiveness of CTC and COL. CTC was found to be dominant or cost-effective in three studies, assuming the most favourable scenario. COL was found to be not cost effective in one study.

CONCLUSIONS

CTC has the potential to be a cost-effective CRC screening strategy when compared to COL. The most important assumptions that influenced the cost-effectiveness of CTC and COL were related to CTC threshold-based reporting of polyps, CTC cost, CTC sensitivity for large polyps, natural history of adenoma transition to cancer, AAA parameters and importantly, adherence. There is a strong need for a differential consideration of patient adherence and compliance to CTC and COL. Recent research shows that laxative-free CTC screening has the potential to become a good alternative screening method for CRC as it can improve patient uptake of screening.

Synchronous triple carcinoma of the colon and rectum

Synchronous multiple colorectal cancers are defined as multiple malignant colorectal tumors that occur simultaneously. All tumors are distant from each other, and none are the result of metastasis from other tumors. Here, we present a case of a 79-year-old man who was admitted to our hospital because of a 3-month history of abdominal pain associated with anemia, loss of appetite, and body weight loss. The patient did not have a family history of cancer. Computed tomography revealed bowel wall thickness and mesentery inflammation at the hepatic flexure of the colon and cecum. Colonoscopy revealed a tumor located 10 cm from the anal verge. Colonoscopic examination of the large bowel was not possible because of bowel obstruction due to the rectal tumor. Synchronous triple adenocarcinoma of the colon and rectum was confirmed by pathologic examination. The tumor was surgically resected by two-segment resection of the colon, low anterior resection, and right hemicolectomy. We used intraoperative colonoscopy to confirm that there were no other lesions after the resection of the three tumors. To the best of our knowledge, this is the first case of synchronous triple carcinoma of the colon and rectum in Taiwan. We consider that comprehensive preoperative study, extensive intraoperative exploration, and radical resection can increase the survival rate of patients with synchronous multiple colorectal cancers.

Teleradiology based CT colonography to screen a population group of a remote island; at average risk for colorectal cancer

PURPOSE

To prospectively assess the performance of teleradiology-based CT colonography to screen a population group of an island, at average risk for colorectal cancer.

MATERIALS AND METHODS

A cohort of 514 patients living in Madeira, Portugal, was enrolled in the study. Institutional review board approval was obtained and all patients signed an informed consent. All patients underwent both CT colonography and optical colonoscopy. CT colonography was interpreted by an experienced radiologist at a remote centre using tele-radiology. Per-patient sensitivity, specificity, positive (PPV) and negative (NPV) predictive values with 95% confidence intervals (95%CI) were calculated for colorectal adenomas and advanced neoplasia ≥6 mm.

RESULTS

510 patients were included in the study. CT colonography obtained a per-patient sensitivity, specificity, PPV and, NPV for adenomas ≥6 mm of 98.11% (88.6-99.9% 95% CI), 90.97% (87.8-93.4% 95% CI), 56.52% (45.8-66.7% 95% CI), 99.75% (98.4-99.9% 95% CI). For advanced neoplasia ≥6 mm per-patient sensitivity, specificity, PPV and, NPV were 100% (86.7-100% 95% CI), 87.07% (83.6-89.9% 95% CI), 34.78% (25.3-45.5% 95% CI) and 100% (98.8-100% 95% CI), respectively.

CONCLUSION

In this prospective trial, teleradiology-based CT colonography was accurate to screen a patient cohort of a remote island, at average risk for colorectal cancer.