New Colon Cancer Screening Test in the Works
Consumer-Friendly Test Under Study; DNA Findings Help Predict Risk
Catching Colon Cancer: The New Test continued...
The test also found tumors on both sides of the colon, Ahlquist says, a feat that is not always accomplished by colonoscopy. "These results were encouraging," he says.
The detection rate was 87% for cancers in stages I through III, considered the most curable, and 69% percent for stage IV, the most advanced.
The test is better at detecting cancer in early stages, he says, because the cells can become less methylated in later stages. The focus of the test is to catch cancers early, he says. "We are targeting early-stage cancers, and that's where the test does the best."
The median age of the patients was 60 (half were older, half younger).
Positive test results would be followed up with colonoscopy.
A clinical trial of the new stool test is expected to start in 2011, he says, and if all goes well the test could be available soon after that.
Ahlquist and Mayo Clinic are working in collaboration with Exact Sciences Corp. of Madison, Wis., to develop the test.
DNA Clues to Colon Cancer
In other research, Lisa Boardman, MD, an associate professor of medicine at Mayo Clinic, wanted to find out if people who develop colon cancer at a younger age than usual are biologically older. (The median age of colon cancer diagnosis is 70, according to the National Cancer Institute.)
To determine biological age, Boardman's team focused on telomeres -- small strips of DNA that cover the end of chromosomes. "They're similar to the protective cap on shoelaces," Boardman says. "Telomeres are a biologic time clock. As we age, our telomeres will become shorter."
She took DNA from the blood of 772 patients diagnosed with colon cancer, all under 60 when diagnosed. She compared the group's telomere lengths to those of 1,660 age-matched healthy patients.
She didn't find what she expected: "We found that longer telomere length was associated with colorectal cancer in people under age 50."
But in those over age 50, those with the longest telomeres had the lowest chance of developing colorectal cancer, she found.
The implications, she says, may be that there are different types of colorectal cancer in younger patients; this in turn may drive different and more effective treatments.