Research focuses on colonoscopy, fecal immunochemical testing, and stool DNA testing.
Randomized trials of screening colonoscopy have been initiated in northern Europe, Spain, and the U.S.. In the Spanish and U.S. trials, participants not assigned to colonoscopy are undergoing fecal immunochemical testing (FIT). Researchers from the Spanish trial have now reported results from the first round of screening. Participation rates were lower in the colonoscopy group than the FIT group (25% vs. 34%). Of people who underwent FIT, 7% had positive tests that were followed by colonoscopy. In intention-to-screen analyses, colorectal cancer (CRC) was found in equal numbers of participants in the two groups (0.1%), but advanced adenomas were found in twice as many colonoscopy participants as FIT participants (2% vs. 1%).
In the U.S. National Polyp Study, researchers evaluated the effects of colonoscopic removal of adenomatous polyps. Patients underwent colonoscopy between 1980 and 1990 to further evaluate symptoms or other positive tests. Among 2602 patients in whom adenomas were removed, 20-year cumulative mortality from CRC was 0.8%. According to population-based registry data, expected CRC mortality was 1.5%; thus, colonoscopic removal of adenomas lowered mortality by roughly 50%.
Research on stool DNA testing ? which should identify colorectal neoplasia more accurately than fecal occult blood testing ? is also moving forward. U.S. investigators applied a ?next-generation? DNA test (which detects 6 neoplasia-associated genes in exfoliated tumor cells) to stool samples from 293 people with normal colonoscopies, 133 patients with advanced adenomas, and 252 patients with CRC (mostly nonmetastatic); stool samples were obtained prior to colonoscopy or surgery. When specificity was set at 90%, sensitivity was 85% for cancer and 54% for adenomas 1 cm. Sensitivity rose to 77% for adenomas >2 cm.
Comment: The first of these studies ? with its low participation rates ? illustrates the difficulties of conducting a randomized trial of colorectal cancer screening. Although the second study supports the efficacy of colonoscopic polypectomy to prevent cancer-related deaths, it is not a randomized screening trial. And the third study suggests that stool DNA screening might eventually enable us to limit colonoscopy to those most likely to benefit.
Source: Journal Watch General Medicine
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