One of the biggest benefits from the continuing plunge in DNA testing costs is going to be earlier diagnosis of cancers. One DNA test under development for colon cancer detection will be usable at home.
David Ahlquist, M.D., professor of medicine and a consultant in gastroenterology at the Mayo Clinic in Rochester, said much of that low rate may be due to inconveniences associated with conventional approaches.
"There is definitely an incentive and legitimate justification to be designing a screening approach that is user friendly, affordable and has the ability to detect pre-cancers," said Ahlquist. "The noninvasive stool DNA test we have developed is simple for patients, involves no diet or medication restriction, no unpleasant bowel preparation, and no lost work time, as it can be done from home. Positive tests results would be followed up with colonoscopy."
Some might think "home stool DNA tester, how gross". But I'll tell you what's gross: watching an adult you've known and loved for years experiencing excruciating pain from cancer metastases throughout their bones while they lose so much weight that they shrink up to skin-and-bones worse than concentration camp survivors.
The test that Ahlquist and colleagues evaluated is under development by Exact Sciences, a molecular diagnostics company in Wisconsin.
The test, which is not yet approved by the FDA, is conducted using a stool sample and works by detecting tumor-specific DNA alterations in cells that are shed into the stool from pre-cancerous or cancerous lesions.
As Nicholas Wade reports, the Exact Sciences test is one of two colon cancer DNA tests headed to market. The second test would require a blood sample.
The other test looks in blood for changes in a single gene, called Septin 9, which is not in the Exact Sciencesí panel of four genes. The test has been developed by Epigenomics AG in Germany. Both tests would be less expensive than colonoscopy, and potentially more effective. Compliance with colonoscopy is low, since people donít want to have one, and the overall cost per detection is high because most people are healthy, and even colonoscopy misses many tumors in the upper part of the intestine.
Click thru and read Wade's articles for the caveats. But note that whatever limitations these tests have today they are just the beginning.
You only get colonoscopy results when you go to the trouble, cost, and small but real risk of getting a colonoscopy. Whereas a home DNA test would cost much less and could be done much more often. The higher frequency of testing would in theory catch the cancer at a much earlier stage. Once the home DNA test turns up positive the person could go in for a colonoscopy to remove polyps or other growths.
Since some cancers develop literally over almost 2 decades early diagnosis opens up the potential of finding and removing cancers long before they become life threatening. Once home tests of blood and saliva for DNA (and likely for antigens) to detect cancer become cheap and widely available the challenge is going to be to find the early stage cancers. Early stage means they will be small. How to find them?
If the tests can narrow down the cancer source to a single organ then excising the cancerous tissue might not be continue to be necessary. Eventually we'll be able go in for new replacement organs. If a test could, for example, indicate presence of a pancreatic cancer 10 years before it will metastasize then in 2030 the solution might be to start growing a new one in a lab. Get the new one after 6 months or a year and toss out the old one.
|Share |||Randall Parker, 2010 October 31 07:16 PM Biotech Cancer|