Fecal DNA Test

Unlike FOBT or FIT, fecal DNA test (or stool DNA test) does not look for blood, but genetic changes specific to polyp cells or cancer.

Over time, the cells of the colon are released into the intestinal lumen (by exfoliation) and from there go to the stools where they can be detected and analyzed.

In fact, cancer cells characteristics – rapid multiplication and resistance to death – help the fecal DNA test, because not only there will be high numbers of cells in the stool, but also many alive (so with intact DNA) 

Samples are kept in the cold (on ice during transport), and should be analyzed within 24 hours of being collected to assure that the DNA is as intact as possible.

Fecal DNA testing “targets” mutations linked to colorectal cancer

Most colorectal cancers result from mutations in cells of the intestinal mucosa; the fecal DNA test screens these cells from stool, looking for mutations in the genes known to be linked to the disease (e.g., Kras, p53 and APC).

Using this test, it is also possible to spot microsatellite instability (MSI); these are DNA regions that become highly unstable (prone to mutations) when a DNA repair gene is faulty (e.g., MLH1, MSH2 and MSH6). 
MLH1, MSH2 and MSH6 genes are known to be linked to colorectal cancer.

Fecal DNA test, although not invasive, is for now extremely expensive. As in other tests, if positive, a colonoscopy will be necessary.