NEJM study endorses CT colonography as primary screening tool
"CT colonography could be adopted into the mainstream of clinical practice as a primary option for colorectal cancer screening. We hope that this additional, less-invasive option for cancer screening will lead more people to get screened and will ultimately result in fewer deaths from colorectal cancer," said ACRIN National CT Colonography Trial principal investigator C. Daniel Johnson, MD.
The ACRIN (American College of Radiology Imaging Network) trial is sponsored by the National Cancer Institute.
Johnson from the Mayo Clinic in Scottsdale, Ariz., and colleagues evaluated 2,531 asymptomatic study participants, 50 years of age or older, at 15 study centers. To qualify for the study, male and female outpatients had to be scheduled for screening colonoscopy and had not undergone a colonoscopy in the past five years. They acquired CT colonographic images with the use of standard bowel preparation, stool and fluid tagging, mechanical insufflation and multidetector CT scanners (with 16 or more rows).
Radiologists reported all lesions measuring 5 mm or more in diameter. They performed optical colonoscopy and histologic review according to established clinical protocols at each center.
The authors said that their primary end point was detection by CT colonography of histologically confirmed large adenomas and adenocarcinomas (10 mm in diameter or larger) that had been detected by colonoscopy. They also evaluated the detection of smaller colorectal lesions (6 to 9 mm in diameter).
For large adenomas and cancers, Johnson and colleagues found that the mean per-patient estimates of the sensitivity, specificity, positive and negative predictive values and area under the receiver-operating-characteristic curve for CT colonography were 0.90, 0.86, 0.23, 0.99 and 0.89, respectively.
The sensitivity of 90 percent indicates that CT colonography failed to detect a lesion measuring 10 mm or more in diameter in 10 percent of patients, according to the investigators. The per-polyp sensitivity for large adenomas or cancers was 0.84. The per-patient sensitivity for detecting adenomas that were 6 mm or more in diameter was 0.78.
“Despite the consensus opinion that colorectal cancer screening is effective, adherence to current guidelines remains low among adults eligible for screening,” the authors wrote.
Johnson and colleagues wrote that the guidelines for “colorectal-cancer screening support multiple test options so that patients and providers can work together to determine their preferred method of examination.” They added that the “less invasive nature of CT colonography and the low risk of procedure-related complications, as compared with colonoscopy, may be attractive to patients and may improve screening-adherence rates by addressing certain concerns of both patients and providers.”
"Previous single-site studies had indicated that CT colonography held promise in screening for colorectal cancer due to its accuracy, safety, cost-effectiveness and patient acceptability. However, validation of the technique across multiple centers and radiologists was needed to provide more evidence of the exam's viability. The ACRIN trial has now validated that CT colonography could serve as an initial screening exam for the population in which screening is indicated," said trial statistician Mei-Hsiu Chen, PhD, from Brown University in Providence, RI.