Prospective Clinical Validation of an Assay for Methylated SEPT9 DNA in Human Plasma as a Colorectal Cancer Screening Tool in Average Risk Men and Women ≥50 Years

Abstract

BACKGROUND & AIMS: In screening for colorectal cancer (CRC), a blood-based screening test with appropriate sensitivity and specificity could provide increased convenience and safety compared with other screening modalities. Two previous case-control studies of clinically confirmed CRC suggested that detection of methylated SEPT9 DNA (mSEPT9) in human plasma can indicate the presence of CRC. The purpose of this study was to prospectively validate sensitivity and specificity of mSEPT9 in a screening setting. METHODS: With ethics board approvals, we recruited and consented subjects (greater-than or equal to)50 years who were scheduled for screening colonoscopy in gastroenterology practices in the United States and Germany. Subjects provided blood samples before preparation for endoscopy. Results of endoscopy were obtained, including histopathology and postoperative reports for persons with polyps and CRC. A real-time polymerase chain reaction assay was used to detect the presence of mSEPT9 in 2 separate aliquots (nullwellsnull) of plasma. Three independent laboratories blinded to clinical data performed the analysis for all cases of cancer and adenomas with high-grade dysplasia, and a stratified sample of other subjects. Test parameter estimates were adjusted to the US and German populations by age and gender, and nonparametric bootstrap confidence intervals were calculated. RESULTS: A total of 7938 men (45%) and women (55%) with an average age of 60 years (inter quartile range, 54-66) were recruited from 32 practices. Laboratory results for 53 cancers and for 1454 subjects with either advanced adenomas (313), nonadvanced adenomas (211), or no pathology (930) yielded a sensitivity for cancer of 50% (95% confidence interval [CI], 34%-65%) and a specificity of 91% (95% CI, 90%-93%). Crude sensitivity ratios by stage were: I, 8/22; II, 8/14; III, 7/12; and IV, 4/5. CONCLUSION: These results demonstrate that CRC can be detected, in a screening setting, among persons of (greater-than or equal to)50 years old by examination of serum for mSEPT9. Pending possible further improvement of test characteristics, the current test might be used to screen individuals unwilling or unable to undergo other screening examinations.