When screening for clinically significant potentially cancerous polyps, computed tomographic colonography (CTC), also known as virtual colonoscopy, administered without laxatives is as accurate as conventional colonoscopy, according to a study published in the May 15 issue of Annals of Internal Medicine.
With laxative-free CTC, patients can avoid bowel cleansing before the exam and instead begin a low-fiber diet 2 days before the test. A tagging agent is ingested the day before the exam. It mixes with residual material in the colon and can then be identified and removed digitally when radiologists interpret the scans.
“The use of laxatives is often viewed as the worst aspect of having not only a virtual colonoscopy but an optical colonoscopy,” said coauthor and site principal investigator Judy Yee, MD, chief of radiology at the San Francisco VA Medical Center (SFVAMC) and professor and vice chair of radiology at the University of California San Francisco (UCSF). “I hope that this research will encourage patients who have delayed screening for colon cancer to be examined with this less invasive method.”
The study, performed jointly at SFVAMC, UCSF, and Massachusetts General Hospital, included 605 patients aged 50 to 85 years. Researchers assessed the accuracy of laxative-free CTC in identifying lesions 6 mm or larger compared with standard optical colonoscopy (OC).
Compared with standard OC exams, which were 95% accurate, Yee and colleagues found that laxative-free CTC exams detected clinically significant polyps 10 mm or larger with 91% accuracy. Scan sensitivity using laxative-free CTC decreases with polyp size, as it does for standard OC, Yee said. Sensitivity for CTC was 59% for polyps measuring 6 mm, compared with standard colonoscopy at 76%.
During the study, cancerous polyps were identified by both the laxative-free virtual colonoscopy and the standard OC exam in 3 of the 605 patients.
When surveying the participants about their experiences while preparing for the examinations, researchers discovered that laxative-free virtual colonoscopy scored higher on all patient survey questions, and more participants indicated the laxative-free virtual colonoscopy to be their exam type of choice.
Yee predicts that, once radiologists are trained in reading the new images and gain experience with the exam process, laxative-free CTC exams will be available wherever virtual colonoscopies are performed.
Source: UCSF.
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