Alaska Natives are twice as likely to get colon cancer and die from the disease than the white population in the United States. When Mayo Clinic doctor David Ahlquist took a trip to Bethel, Alaska in the mid-1990’s 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 said.
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 bacteria 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 as the presence of cancer or polyps,” he explains.
The test is expected to cost about $300, far less than the average colonoscopy in Alaska. Ahlquist compares his research to the advent of the pap smear.
“The pap smear took a target, cervical cancer, which at that time, in the ’50’s was the number one cancer killer in women in the United States. Now, it’s essentially been eradicated in women who are screened,” Ahlquist said.
According to two studies published this year, the DNA colon cancer test finds 85 percent of colon cancers and more than 50% 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.”
But Burt thinks it has to get better at detecting pre-cancerous polyps.
“Is it enough to replace colonoscopies so we only do colonscopies 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, 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. A hundred patients have enrolled.
If the FDA grants approval, the test could be available as soon as the middle of next year.