(ChemotherapyAdvisor) – Using a newer, laxative-free computed tomographic colonography (CTC or “virtual colonoscopy”) method may increase the likelihood patients will participate in screening for colorectal cancer; however, this technology will miss adenomas <10mm, a prospective study published in the May 15 issue of Annals of Internal Medicine has found.
The newer procedure utilizes a computer program to “cleanse” the colon electronically for radiologic evaluation and, in this study, “correctly identified 91% of persons with adenomas 10mm or larger,” Michael E. Zalis, MD, and colleagues from Massachusetts General Hospital, Boston, MA, and the University of California, San Francisco, San Francisco, CA, noted.“Moreover, patients reported a better experience with CTC examination preparation over standard, cathartic preparation.”
The prospective study assessed the performance of detecting adenomas ≥6mm and patient experience in 605 adults aged 50 to 85 years at average to moderate risk for colon cancer who were screened using laxative-free CTC followed by traditional colonoscopy in multicenter, ambulatory imaging and endoscopy centers. Prior to undergoing laxative-free CTC, patients adhered to a low-fiber diet and ingested a small dose of contrast material to tag feces thoroughly. After images were taken, computer software removed tagged feces from the colon images without altering the size or appearance of mucosal folds and polyps.
“The optical colonoscopy examinations were initially blinded to CTC results, which were subsequently revealed during colonoscope withdrawal; this method permitted reexamination to resolve discrepant findings,” they wrote. Unblinded optical colonoscopy served as a reference standard.
For adenomas ≥10mm, per-patient sensitivity of CTC was 0.91 and specificity was 0.85; sensitivity of optical colonoscopy was 0.95 and specificity was 0.89. Sensitivity of CTC was 0.70 for adenomas ≥8mm and 0.59 for those ≥6mm or larger; for adenomas ≥8mm and ≥6mm, sensitivity of optical colonoscopy was 0.88 and 0.76, respectively. Specificity of optical colonoscopy at the threshold of ≥8mm was 0.91 and, at ≥6mm, 0.94.
Specificity for optical colonoscopy was greater than that for CTC, which was 0.86 at the threshold of ≥8mm and 0.88 at ≥6mm (P=0.02). Reported participant experience for comfort and difficulty of examination preparation was better with CTC than optical colonoscopy.
“Readers deemed most cases adequate for interpretation, and we observed no major adverse events with either technique,” they noted. “These results suggest that laxative-free CTC may provide an alternative for persons in whom laxative bowel preparation is a barrier to colorectal cancer screening.” Study limitations included that the survey instrument was not independently validated and only 3 expert radiologist readers reviewed CTC results.