DNA-based test for colon cancer, costing US$599 a go, approved by US

The United States Food and Drug Administration has approved the first screening test for colon cancer that uses patients' DNA to spot potentially deadly tumours and growths.

The Cologuard test from Exact Sciences detects irregular mutations in stool samples that can be an early warning sign of cancer. Patients who test positive should undergo a colonoscopy to confirm the results.

Doctors have long used stool tests to look for hidden blood that can be a warning sign of tumours and precancerous polyps.

But company studies of Cologuard showed that it was more accurate at detecting tumours and polyps than traditional stool blood tests. Cologuard detected 92 per cent of colon cancers and 42 per cent of advanced polyps in a study of 10,000 patients, while traditional blood screening detected only 74 per cent of cancers and 24 per cent of polyps.

The new test was not superior on all counts. Cologuard was less accurate at correctly ruling out cancer, reporting more growths when none were present.

The approval has the potential to reshuffle current medical practice, though FDA officials stressed that DNA-based stool screening had not been endorsed by federal medical advisers who set screening guidelines. A spokeswoman for Exact Sciences, based in the state of Wisconsin, said the test would cost US$599 per patient. A traditional test costs US$25.