Screening for colorectal cancer is widely considered a cost effective intervention with strong evidence supporting mortality reduction in the screened population. Despite this, global screening rates remain low, even in developed countries. Blood based screening tests have the potential to overcome resistance to screening, thereby increasing overall participation, and saving lives.
Here we review the development of a recently US FDA approved blood based epigenetic screening test for colorectal cancer. The Epi proColon test is based on the Septin 9 (SEPT9) gene promoter methylation status measured in cell free DNA from plasma. While the assessment of DNA methylation has been practiced in laboratories for some time, the approved test provides a standardized and kitted method for isolation of cell free DNA from plasma, reagents and methods for bisulfite conversion and purification of converted DNA (bisDNA) in preparation for DNA methylation analysis by real time PCR. This enables broad dissemination of DNA methylation based testing to laboratories approved to perform standard molecular diagnostics.
In clinical trials, the approved Epi proColon test had sensitivity for colorectal cancer of 68-72%, comparable to commonly used stool tests, at a specificity of 80-82%. The test was well received, with 99.5% of patients in a participation trial agreeing to testing, and of these, when the test was positive, 67% scheduled colonoscopy. Finally, 59% of patients who had a colonoscopy in this study had a finding requiring polypectomy or biopsy. Based on these data, the test was approved as a screening test in the US, for patients who are otherwise unscreened, a key advance for molecular diagnostics applications in the field of clinical epigenetics.
Theo deVos and Bela Molnar