Can A Colon Cancer Test Level The Playing Field For Alaska Natives?
Alaska Natives are twice as likely to get colon cancer and die from it as the white population in the United States. When Mayo Clinic doctor David Ahlquist took a trip to Bethel, Alaska, in the mid-1990s, that startling statistic caught his attention.
"Here they had one of the world's highest rates of colon cancer and one of the world's poorest outcomes in terms of survival from cancer, because of late diagnosis," Ahlquist says.
The best way to prevent colon cancer is through screening, but Ahlquist realized that approach has flaws in rural Alaska. Colonoscopy equipment isn't available in remote Native villages. A widely used test that detects blood in stool isn't effective because many Alaska Natives have a stomach bacterium called H. pylori that also causes bleeding.
The colon cancer screening rate for Alaska Natives in some rural areas of the state is as low as 23 percent. In urban areas, it's closer to 60 percent.
So Ahlquist began working on a test that can identify several altered genes that are present in colon cancer.
"It measures DNA changes that are shed from the surface of cancer or pre-cancer into the stool, and we can detect those changes that act as a signature of the presence of cancer or polyps," he explains.
Ahlquist compares his research to the advent of the Pap smear. When that test was invented in the 1950s, cervical cancer killed more women in the U.S. than any other cancer. "Now it's essentially been eradicated in women who are screened," Ahlquist says.
According to two studies published this year, the DNA colon cancer test finds 85 percent of colon cancers and more than 50 percent of pre-cancerous polyps. Ahlquist and the Mayo Clinic are working with a company called Exact Sciences to commercially develop the test, and both will benefit financially if it comes on the market.
Dr. Randall Burt at the Huntsman Cancer Institute in Utah has high hopes, too. "In the end, it could be a huge game changer," he says.
But Burt thinks the test has to get better at detecting pre-cancerous polyps.
"Is it enough to replace colonoscopies so we only do colonoscopies on people with a positive stool test? Probably not yet. But it's getting there," he says.
Dr. William Grady of the Fred Hutchinson Cancer Research Center in Seattle agrees that with more rigorous study, these tests could change cancer diagnosis and treatment. He is working on another version of a DNA-based stool test for colon cancer detection. DNA tests are also in the works for a long list of cancers including, lung, pancreatic and brain cancer.
"It's very exciting," Grady says. "I think we're going to really see a revolution in the way we take care of patients who have cancer."
In Alaska, the Alaska Native Tribal Health Consortium began a three-year trial of Ahlquist's colon cancer DNA test. One hundred patients have enrolled.
If the FDA grants approval, the test is expected to cost about $300, far less than the average colonoscopy in Alaska. It could be available as soon as the middle of next year.
This story is part of a project with the Alaska Public Radio Network, NPR and Kaiser Health News.
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