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Shots - Health Blog
Thu June 14, 2012
Can A Colon Cancer Test Level The Playing Field For Native Alaskans?
Originally published on Thu June 14, 2012 7:56 pm
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.
AUDIE CORNISH, HOST:
It's ALL THINGS CONSIDERED from NPR News. I'm Audie Cornish. Colon cancer is the second deadliest cancer in the U.S. behind lung cancer and scientists are trying to make it easier to spot. Several new tests that use DNA samples could do that.
A Mayo Clinic doctor came up with one of them after he went to rural Alaska. He realized people in remote areas have trouble just getting screened. Alaska Public Radio Network's Annie Feidt reports.
ANNIE FEIDT, BYLINE: When Mayo Clinic Dr. David Ahlquist took a trip to Bethel in western Alaska in the mid-1990s, a startling statistic came to his attention. Alaska natives were and still are twice as likely to get colon cancer and die from the disease as Caucasian Americans.
DAVID AHLQUIST: 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.
FEIDT: He realized traditional screening methods had flaws in places like rural Alaska. Colonoscopy equipment isn't available in remote native villages and a widely used test that detects blood in stool isn't effective because many Alaska natives have stomach bacteria called H-pylori that also cause bleeding. The colon cancer screening rate for Alaska natives in some rural areas of the state is as low as 23 percent.
So, when he returned to the Mayo Clinic, Ahlquist began working on a new kind of test. He wanted it to be highly accurate, accessible to anyone and easy to use. The test he eventually developed can identify several altered genes that are only present in colon cancer.
AHLQUIST: It measures DNA changes that are shed from the surface of cancer or pre-cancers into the stool and we can detect those changes that act as a signature of the presence of cancer or polyps.
FEIDT: According to two studies published this year, the DNA 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.
Ahlquist says the test could represent a revolution for colon cancer screening, much like the pap smear did for cervical cancer half a century ago.
AHLQUIST: The pap smear took a target, cervical cancer, which, in the '50s, was the number one cancer killer in the United States among women. Now, in those women who are screened with the pap smear, it's a rare disease. It's essentially been eradicated in women who are screened.
FEIDT: That may sound like a bold claim, but it's one that has merit, according to Dr. Randall Burt, director of prevention at the Huntsman Cancer Institute in Utah.
RANDALL BURT: Well, in the end, it could be a huge game changer.
FEIDT: Burt has been watching the development of the colon cancer test over the years as an outside observer and he thinks it's fair to say the DNA test could one day be compared to the pap smear, especially if it gets better at detecting pre-cancerous polyps.
BURT: Is it enough to replace colonoscopies so that we only do colonoscopy on people with a positive stool test? Probably not yet, but it's getting there.
FEIDT: In anticipation of FDA approval early next year, the DNA test is undergoing a trial at more than 100 sites in the U.S. and Canada. There's no guarantee it will pass that final hurdle and Burt says it's important for the test to prove itself in that more rigorous study.
In Alaska, there's hope Ahlquist's colon cancer DNA test could help make the disease less deadly. In February, the Alaska Native Tribal Health Consortium began a three-year trial of the test. One hundred patients have enrolled so far.
Janet Kelly is cancer surveillance director at ANTHC. She says the test holds a lot of promise for Alaska natives.
JANET KELLY: Until we can find a cure for this cancer, the best we have is to screen and early detection is - through this test, offers a lot of opportunity.
FEIDT: It's 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.
For NPR News, I'm Annie Feidt in Anchorage. Transcript provided by NPR, Copyright National Public Radio.