Exploring Blood-based Colorectal Cancer Screening

More studies need to be done to determine the reliability of circulating cell-free DNA (ccfDNA) testing to detect colorectal cancer. Among other things, the additional research will help scientists understand false positive and false negative results, writes Victoria M. Pratt in an editorial recently published in Clinical Chemistry. Pratt’s editorial also explores other options for detecting colorectal cancer.

ccfDNA testing is “gaining momentum in clinical testing because ccfDNA can easily be isolated from the circulation (e.g., plasma) and other body fluids of patients,” Pratt writes. It could prove a useful alternative for patients who would like to avoid more cumbersome methods of testing, such as colonoscopy. “There is no ick factor in a routine blood draw compared to stool-based testing or the preparation needed for a colonoscopy procedure,” the editorial states.

A study published in the same issue of Clinical Chemistry describes a blood-based assay used to detect ccfDNA methylated septin 9 (mSEPT9). The study describes the diagnostic accuracy of colonoscopy screening for colorectal cancer compared to that of the Epi proColon assay in screened individuals of multiple ethnic backgrounds. Pratt writes, “Overall, clinical sensitivity was 68% (95% CI 53%–80%), clinical specificity 79% (95% CI 77%–81%), positive predictive value 8%, and negative predictive value 99%.”

The study authors also observed several false negatives when mSEPT9 was compared to colonoscopy. Because of this and concerns about false positive results, Pratt concludes that further research is needed to build on the interest generated by the newly published study.