Data on Exact Sciences' ($EXAS) colorectal cancer screening test, presented at the 11th Annual AACR International Conference on Frontiers in Cancer Prevention Research, suggest that the assay could pick up the DNA changes and traces of blood that signal precancers and the very earliest stages of cancer, when treatment is at its most effective. Current tests rely on fecal blood and are limited in their ability to identify the precancers.
The researchers analyzed 1,003 patient stool samples before colonoscopy in patients that were being screened or monitored for early signs of cancer, or 7 days after colonoscopy in patients with large precancers or colorectal tumors.
"By analyzing samples with confirmed diagnoses from colonoscopy, we were able to build an analytic algorithm that combines our 11 stool-based biomarkers into a single result," said Graham P. Lidgard, senior vice president of R&D and chief science officer at Exact Sciences.
The test was able to pick up 98% of cancers and 57% to 83% of precancers. Exact Sciences, which floated in August, is involved in a study collecting samples from more than 10,000 patients before screening colonoscopy, and plans to apply for FDA approval after the study.
In another study, screening for DNA mismatch repair (MMR) genes was effective at spotting patients with Lynch syndrome, the most common form of hereditary colorectal cancer. Identifying the patients at risk enables intensive screening and prophylactic surgery, reducing the incidence of these tumors, and cutting the risk of death. The research was published in JAMA, and as an accompanying editorial points out: "The potential benefits [of screening] must outweigh the risks. The aggregate costs of screening and its consequences must be acceptable."
This is true for all forms of population screening, and needs to be borne in mind when developing new biomarker-based tests.