Report in English with a Dutch summary (KCE reports 45A)

KCE reports vol.45 Screening for Colorectal Cancer 71
In a small population based case-control study in Germany 318; including 380
cases and 485 controls, detailed history and results of previous colonoscopies
were obtained by interview and from medical records and adjusted relative
risks of colorectal cancer among subjects with a previous negative colonoscopy
compared with those without previous colonoscopy were estimated according
to time since colonoscopy. Subjects with previous negative colonoscopy had a
74% lower risk of CRC than those without previous colonoscopy (OR 0,26;
95% CI 0,16 to 0,40). This low risk was seen even if the colonoscopy had been
done up to 20 or more years previously. Particularly low risks were seen for
rectosigmoid cancer (OR 0,13; 95% CI 0,04 to 0,43) and for rectal cancer (OR
0,19; 95% CI 0,09 to 0,39), and after a negative screening colonoscopy at ages
55 to 64 (OR 0,17; 95% CI 0,08 to 0,39) and 65 (OR 0,21; 95% CI 0,10 to
0,41). The authors concluded that subjects with negative findings at
colonoscopy are at very low risk of colorectal cancer and might not need to
undergo repeat colonoscopy for 20 years or more, if at all. The possibility of
extending screening intervals to 20 years or more might reduce complications
and increase the feasibility, compliance and cost-effectiveness of colonoscopy
based screening programs.
5.4.4 Double contrast barium enema (DCBE)
With this conventional radiological technique, a liquid barium mixture is instilled
into the colorectum and afterwards air is insufflated, followed by x-ray
examination in various positions 275, 194. The patient usually prepares with dietary
restrictions and an enema or laxatives the day before. It is a standard
radiological technique and was considered as a potential screening tool. It does
have the advantage of a higher sensitivity compared to FOBT, the ability to
visualise the entire colon compared to FS and a better safety and lower cost
compared to colonoscopy. It does not permit, however, to take samples
meaning that colonoscopy will still be needed when suspicious lesions are
detected by DCBE. The Scientific Steering Committee considered DCBE as an
obsolete technique for mass screening purposes.
5.4.5 Virtual colonoscopy
Virtual colonoscopy (also known as CT colonography, CT pneumocolon, MRI
colonoscopy) refers to essentially preoperative (i.e. diagnostic) radiological
tumor staging techniques 319 using computer generated images of the colon
constructed from data obtained from an abdominal CT 194, 320-323 or MRI
examination 324-327.
The preparation is similar to standard colonoscopy. Air or carbon dioxide is
insufflated into the colon and data are acquired by the scanner, generating
images of the colon. Data are presented as two-dimensional images while
suspicious areas can be rendered as three-dimensional images 328. Sedation is
normally not required although mild discomfort is reported from the insufflation
of air during the procedure 231.
Theoretically, virtual colonoscopy has several potential advantages over
endoscopic colonoscopy for use in colorectal cancer diagnosis and potentially
even screening. It enables to visualise the entire colon non-invasively and can
also identify malignancies in areas that are difficult to assess with colonoscopy.
Therefore, it has been argued that, in a diagnostic setting, it might be the
favoured examination technique when colonoscopy failed, was incomplete or
when the performance of a colonoscopy was contra-indicated or refused by the
patient 329, 330. It is a rapidly evolving technique as witnessed by the wealth of