Colon cancer test works without colonoscopy

Exact Sciences’ new test detected 87 percent of stage I, II and III colon tumors, which can be surgically removed, and found 64 percent of the biggest pre-cancerous growths, the researchers told a meeting of the American Association for Cancer Research.

It finds altered DNA that has either turned a cell cancerous, or has started the changes that lead to cancer.

“The noninvasive stool DNA test we have developed is simple for patients, involves no diet or medication restriction, no unpleasant bowel preparation, and no lost work time, as it can be done from home,” said Dr. David Ahlquist of the Mayo Clinic in Rochester, Minnesota, who developed the test.

“Positive tests results would be followed up with colonoscopy.”

Mayo has licensed the test to Exact Sciences, which believes it has the potential to reach sales of $1bn in the United States alone.

The test looks for three genes that have been altered in a process called methylation.

Colorectal tumors develop in the lining of the colon and in the rectum. As fecal matter passed through the tract, it collects some cells from these growths. The test can find even tiny amounts of altered DNA from these growths in a stool sample.

Studies of 1,100 patients showed the test detected 64 percent of precancerous growths called adenomas that were bigger than 1 cm (0.4 inch), which is considered the size most likely to turn into a tumor.

It found 85 percent of cancers, and 87 percent of the earlier-stage cancer that can potentially be cured by surgical removal.

New tool
“This is the first study of a stool DNA test to show such promising results in detecting colorectal pre-cancer,” Ahlquist said in a statement.

“Colorectal cancer is a treatable disease if caught early, and this test shows great promise as a potential addition to other available screening tools.”

Colorectal cancer is the second-leading cancer killer in the United States and other developed countries.

The American Cancer Society estimates there will be about 122,000 new cases of colon cancer in 2010, with more than 51,000 deaths.

It recommends that all Americans start getting tested for the disease at age 50.

In standard colonoscopies, a tiny camera is threaded up through the rectum. The device has a little pair of clippers on the end to remove suspicious-looking growths called polyps so they can be tested to see if they might become cancerous.

But only about half of those who should get tested do, in part because the procedure is embarrassing, uncomfortable and can, in rare cases, cause injury.

Exact Sciences hopes a home-based test would be a big seller and health experts hope it would encourage more people to get screened.

The company has said earlier it would aim for a charge of about $300 to $400 per test, and plans to submit for US Food and Drug Administration approval in 2012.

Danish biotech company Exiqon and Belgian biotech firm OncoMethylome are developing blood tests for colon cancer.