Comparsion of computed tomography colonography with magnetic resonance colonography for use in colorectal cancer screening.

Colorectal cancer is the second leading cause of cancer death in the Western
world. The Dutch government stated in May 2006 that it should be possible to
start colorectal cancer screening in 2010. The major outstanding issue is the
choice of method of initial detection of polyps or cancers.
Since 2005 promising results have been obtained with CT colonography as a less
invasive screening method. Detection accuracy similar to colonoscopy has been
reported. The disadvantage of the use of CT is the exposure to radiation. MRI
would have an obvious advantage over CT in colorectal cancer screening in the
lack of exposure to radiation but studies using MR colonography have been
limited to small patient samples and it has never been directly compared to CT
colonography.

This study aims to compare CT and MR colonography in symptomatic patients
referred for investigation by colonoscopy. The overall sensitivity and
specificity for colonic adenomas, sensitivity and specificity for advanced
adenomas (>10mm or high grade dysplasia), and patients experiences and
preferences during the 3 procedures will be assessed.

To compare the sensitivity and specificity of MR colongraphy with that of CT
colonography for the detection of colonic neoplasms, compared to colonoscopy as
"gold standard".

222 patients will undergo standard colonic preperation with laxatives and
undergo both a CT colonography and an MR colonography on the same day. For both
the colon will be insufflated with CO2 and an intravenous antispasmodic
administered, after which 2 scans will be made in prone and supine position.

Patients will undergo 2 scans both lasting approximately 1/2 hour. Before this
they will be required to take laxatives to clean the colon. During the 2 scans,
an intravenous antispasmodic and an intravenous constrast agent will be
administered and the colon will be inflated with CO2 via a rectal cannula.

Risks: radiocontrast allergy, bowel perforation bij insufflation (<1/5000),
discomfort with bowel insufflation

Benefits: extracolonic lesions can be identified. Intracolonic lesions missed
by colonoscopy can be identified.