A new generation of DNA tests for colon cancer seems likely to improve the detection both of cancers and of the precancerous polyps that precede them. The tests, if validated, could reduce the burden of disease substantially by detecting tumors at an early stage, including those not picked up by a colonoscopy.

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.

Researchers turned to measuring mutations in DNA after Dr. Bert Vogelstein of Johns Hopkins University discovered the series of mutations by which a colon polyp advances to full cancer. But no single mutation predicts a patient’s risk, and the mutation tests, though more accurate than the blood tests, have not been a decisive improvement.