CHICAGO (AP) -- Even if President Bush and Katie Couric might make it seem that way, getting screened for colorectal cancer isn't easy. But that may be about to change.

The most accurate screening procedure -- colonoscopy -- is uncomfortable and embarrassing, meaning many people who need it never get it.

Other procedures like flexible sigmoidoscopy and fecal occult blood testing, though not as invasive, are no less embarrassing and require the patient to alter his or her diet. Worse, they frequently yield false positive results or fail to find existing cancers.

Don Hardison, president and chief executive of Exact Sciences Corp., once received a positive result for colon cancer after having such a test, only to find after further testing that he was cancer free.

Now his Maynard, Mass. applied genomics company has developed a test for colorectal cancer that taps into the science of the human genome, promising ease of use, better detection and less need for a red face.

The PreGen-Plus, which Exact hopes to introduce next year, features proprietary technology that can detect cancer-indicating mutations in human DNA extracted from the stool. The test requires no dietary changes and causes no discomfort. A user just produces a sample and mails it to the laboratory in a sealed container.

"There's no diet modification, no bowel preparation," Hardison said in an interview. "You can do the test in the privacy of your own home and it's shipped back to the lab. You just do something you probably do every day anyway."

Colon cancer kills 57,000 Americans a year and is the deadliest cancer among non-smoking men and women. But if it's caught early, the five-year survival rate is more than 90 percent. The problem is persuading people to get tested. About 80 million Americans over age 50 are at risk, but only 12 million to 14 million actually get screened, said Anthony Shuber, chief technology officer at Exact.

The problem is persuading people to get tested. In an attempt to coax people into getting a colonoscopy, journalist Couric had one performed live on television in March 2000 after her husband died of colon cancer. President Bush also had a colonoscopy performed this summer.

A non-invasive test like PreGen-Plus, which analysts think will cost around $500 to $700 and may be able to detect cancer 65 percent to 70 percent of the time, could have a market worth hundreds of millions of dollars, Hardison said.

Based on early studies, accuracy will be about equal to a Pap smear test and compares well with 50 percent sensitivity for sigmoidoscopy and around 30 percent for a single fecal occult blood test, Shuber said.

If the Exact test indicates cancer, 95 percent of the time cancer is there, so the rate of false positives appears low.

Colonoscopy is better than any other test, including PreGen-Plus, with sensitivity of around 90 percent. But the test, which probes the entire colon and requires advance preparation by the patient, can't detect very early changes in DNA that might lead to colon cancer. Some patients have been injured by the procedure.

"Colonoscopy is an expensive test," Hardison said, noting it can cost up to $2,000. "You have to do a bowel preparation that's not a lot of fun, and you miss a day of work. A huge market of people will never do it."

Exact is conducting two U.S. trials of approximately 10,000 patients for PreGen-Plus. The question is whether Exact can have equal success detecting cancer in the general population, as its data to date is based on smaller studies of patients who were, for the most part, symptomatic. The first results, on a study of 5,000 patients, are due by the second half of next year, and will go a long way toward determining whether the product will be a success.

For many years, scientists thought it would be impossible to isolate human DNA from the stool. Some said it simply didn't exist there. But Shuber found a way to do so. The technology can detect various gene mutations, including one in the APC gene that is evident in almost all cases of colon cancer. Because these mutations can occur before there's any other evidence of disease, the test can lead to an earlier diagnosis, raising the survival rate.

Copyright 2002 The Associated Press. All rights reserved.