| Summary: | <p>Abstract</p> <p>Background</p> <p>About half of Americans 50 to 75 years old do not follow recommended colorectal cancer (CRC) screening guidelines, leaving 40 million individuals unscreened. A simple blood test would increase screening compliance, promoting early detection and better patient outcomes. The objective of this study is to demonstrate the performance of an improved sensitivity blood-based Septin 9 (<it>SEPT9</it>) methylated DNA test for colorectal cancer. Study variables include clinical stage, tumor location and histologic grade.</p> <p>Methods</p> <p>Plasma samples were collected from 50 untreated CRC patients at 3 institutions; 94 control samples were collected at 4 US institutions; samples were collected from 300 colonoscopy patients at 1 US clinic prior to endoscopy. <it>SEPT9 </it>methylated DNA concentration was tested in analytical specimens, plasma of known CRC cases, healthy control subjects, and plasma collected from colonoscopy patients.</p> <p>Results</p> <p>The improved <it>SEPT9 </it>methylated DNA test was more sensitive than previously described methods; the test had an overall sensitivity for CRC of 90% (95% CI, 77.4% to 96.3%) and specificity of 88% (95% CI, 79.6% to 93.7%), detecting CRC in patients of all stages. For early stage cancer (I and II) the test was 87% (95% CI, 71.1% to 95.1%) sensitive. The test identified CRC from all regions, including proximal colon (for example, the cecum) and had a 12% false-positive rate. In a small prospective study, the <it>SEPT9 </it>test detected 12% of adenomas with a false-positive rate of 3%.</p> <p>Conclusions</p> <p>A sensitive blood-based CRC screening test using the <it>SEPT9 </it>biomarker specifically detects a majority of CRCs of all stages and colorectal locations. The test could be offered to individuals of average risk for CRC who are unwilling or unable to undergo colonscopy.</p>
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