Califanos team used a different set of seven hypermethylated genes among blood samples as well. Although the blood test was more accurate than the saliva test at detecting cancer in patients with the disease (34 out of 37), there was a trade-off in the number of healthy individuals it spotted (53 of 173).
Few tests can be perfect 100 percent of the time in identifying both normal and cancerous cells, says Califano. Because head and neck cancers are not widespread, it makes more sense to screen those at high risk and to focus on a tests ability to accurately rule out healthy people.
Califano notes that tests designed for broader populations, like PSA, focus on identifying a widespread disease in large numbers of people.
A saliva test, Califano says, is easy to do, painless and cheap, capturing cells from a wide area of the mouth. Some head and neck tumors do not shed genetic material into the blood, making the saliva test a better bet.
The Johns Hopkins investigators said more studies are needed to refine the test by uncovering additional hypermethylated genes that play a role, and to automate the test before multi-institutional clinical trials can begin. One of the first clinical uses for such a test could be to detect recurrence in current head and neck cancer patients.
There are nearly 50,000 cases of head and neck cancer diagnosed in the U.S. annually. Most are found when the disease has spread, and less than a year after diagnosis, many recur. Causes include heavy tobacco and alcohol use. Other head and neck cancers are caused by the sexually transmitted human papillomavirus.
|Contact: Vanessa Wasta|
Johns Hopkins Medical Institutions