Colorectal cancers tend to grow slowly and are easily removed if caught early. But many people over 50 do not comply with the recommendation to have a colonoscopy — a time-consuming procedure in which a tube is threaded up the intestine — and even colonoscopies do not catch everything. Colorectal cancer has become the second most common cancer in the United States; each year it causes more than 50,000 deaths and costs about $14 billion to treat.
Colon tumors provide considerable evidence of their presence by shedding blood and cells that are detectable in the stool. Tests for blood have reduced deaths from colorectal cancer only modestly, because they are not very sensitive to precancerous polyps, the stage at which cancer is best prevented.
The new tests being developed rely on measuring changes in DNA produced by cancerous cells and appear to be more effective than the stool sample tests currently being used.