Laxative-free CT colonography (CTC) provided reasonable accuracy in the detection of adenomas 10 mm or larger and improved patient comfort compared with optical colonoscopy, according to a study published May 15 in Annals of Internal Medicine .
Colon cancer screening has been by hampered by low patient adherence, with patients reporting a general aversion to pre-examination laxative bowel cleansing. Recently, CTC has emerged as a viable, non-invasive alternative to optical colonoscopy. However, like optical colonoscopy, this method also had required laxative bowel preparation. Electronic cleansing software, which digitally subtracts tagged feces from colon images, presents another option.
Michael E. Zalis, MD, of the department of imaging at Massachusetts General Hospital in Boston, and colleagues, designed a prospective study to evaluate the performance of laxative-free CTC and compare it with optical colonoscopy.
The researchers enrolled 694 asymptomatic adults ages 50 to 85 years between June 2005 and October 2010; and obtained complete data for both exams and pathology from 605 participants. Three abdominal radiologists interpreted the CTC studies with the aid of computer-aided detection software and an electronic cleansing program.
In addition, participants were asked to complete a questionnaire assessing the discomfort, difficulty of preparation and severity of bowel symptoms on a five-point scale for laxative-free CTC and optical colonoscopy.
Zalis et al referred to accepted practice in screening, which suggests that adenomas larger than 6 mm be removed. However, 90 percent of lesions with clinically important features are 10 mm or larger, the researchers noted.
In the current study, 85 percent of confirmed lesions with advanced histology were 10 mm or larger. Among adenomas 10 mm or larger, per-patient sensitivity and specificity of laxative-free CTC were 0.91 and 0.85, respectively. Optical colonoscopy provided per patient-sensitivity of 0.95 and specificity was 0.89.
Although sensitivity of CTC was less than optical colonoscopy at the threshold of 6 mm or larger, the radiologists rated 97.1 percent of CTC cases as technically adequate.
Patients reported higher median comfort scores with CTC compared with optical colonoscopy, at 1 and 2, respectively.
“These results suggest that laxative-free CTC can detect the most clinically important polys and could contribute to colon cancer screening,” wrote Zalis and colleagues. Limitations of the study included its size, limited number of readers and quality of survey data.
The researchers noted that the CTC reporting and data system resulted in additional diagnostic work because of extracolonic findings in 5.5 percent of cases.
There are additional advantages of CTC. Importantly, it may be more cost-effective than no screening and also more cost-effective that optical colonoscopy if it improves compliance, according to decision models.