Colonoscopy is the gold-standard test for investigation of symptoms suggestive of colorectal cancer; computed tomographic colonography ( CTC ) is an alternative, less invasive test. However, additional investigation after CTC is needed to confirm suspected colonic lesions, and this is an important factor in establishing the feasibility of computed tomographic colonography as an alternative to colonoscopy.
Researchers have compared rates of additional colonic investigation after computed tomographic colonography or colonoscopy for detection of colorectal cancer or large ( greater than or equal to 10 mm ) polyps in symptomatic patients in clinical practice.
This pragmatic multicentre randomised trial recruited patients with symptoms suggestive of colorectal cancer from 21 UK hospitals.
Eligible patients were aged 55 years or older and regarded by their referring clinician as suitable for colonoscopy. Patients were randomly assigned ( 2:1 ) to colonoscopy or CTC by computer-generated random numbers, in blocks of six, stratified by trial centre and sex.
Researchers have analysed the primary outcome ( the rate of additional colonic investigation ) by intention-to-treat.
1610 patients were randomly assigned to receive either colonoscopy ( n=1072 ) or computed tomographic colonography (n=538).
30 patients withdrew consent, leaving for analysis 1047 assigned to colonoscopy and 533 assigned to computed tomographic colonography.
160 ( 30% ) patients in the CTC group had additional colonic investigation compared with 86 ( 8.2% ) in the colonoscopy group ( relative risk, RR=3.65; p less than 0.0001 ).
Almost half the referrals after computed tomographic colonography were for small ( less than 10 mm ) polyps or clinical uncertainty, with low predictive value for large polyps or cancer.
Detection rates of colorectal cancer or large polyps in the trial cohort were 11% for both procedures.
Computed tomographic colonography missed 1 of 29 colorectal cancers and colonoscopy missed none ( of 55 ).
Serious adverse events were rare.
Guidelines are needed to reduce the referral rate after computed tomographic colonography. For most patients, however, computed tomographic colonography provides a similarly sensitive, less invasive alternative to colonoscopy. ( Xagena )
Atkin W et al, The Lancet 2013; 381: 1194-1202