Computed tomographic colonography compared with colonoscopy in patients at increased risk for colorectal cancer.
OBJECTIVE
To date, computed tomographic (CT) colonography has been compared with an imperfect test, colonoscopy, and has been mainly assessed in patients with positive screening test results or symptoms. Therefore, the available data may not apply to screening of patients with a personal or family history of colorectal polyps or cancer (increased risk). We prospectively investigated the ability of CT colonography to identify individuals with large (>or=10 mm) colorectal polyps in consecutive patients at increased risk for colorectal cancer.


METHODS
A total of 249 consecutive patients at increased risk for colorectal cancer underwent CT colonography before colonoscopy. Two reviewers interpreted CT colonography examinations independently. Sensitivity, specificity, and predictive values were determined after meticulous matching of CT colonography with colonoscopy. Unexplained large false-positive findings were verified with a second-look colonoscopy.


RESULTS
In total, 31 patients (12%) had 48 large polyps at colonoscopy. This included 8 patients with 8 large polyps that were overlooked initially and detected at the second-look colonoscopy. In 6 of 8 patients, the missed polyp was the only large lesion. With CT colonography, 84% of patients (26/31) with large polyp(s) were identified, paired for a specificity of 92% (200-201/218). Positive and negative predictive values were 59%-60% (26/43-44) and 98% (200-201/205-206), respectively. CT colonography detected 75%-77% (36-37/48) of large polyps, with 9 of the missed lesions being flat.


CONCLUSIONS
CT colonography and colonoscopy have a similar ability to identify individuals with large polyps in patients at increased risk for colorectal cancer. The large proportion of missed flat lesions warrants further study.
Van Gelder
Rogier E
RE
Department of Radiology, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands. r.e.vangelder@amc.uva.nl
Nio
C Yung
CY
Florie
Jasper
J
Bartelsman
Joep F
JF
Snel
Pleun
P
De Jager
Steven W
SW
Van Deventer
Sander J
SJ
Laméris
Johan S
JS
Bossuyt
Patrick M M
PM
Stoker
Jaap
J
D000368:Aged; D003111:Colonic Polyps / Q000150:complications / Q000175:diagnosis*; D023881:Colonography, Computed Tomographic / Q000379:methods*; D003113:Colonoscopy / Q000379:methods*; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D012306:Risk; D012680:Sensitivity and Specificity