WEDNESDAY, Nov. 28 (HealthDay News) -- A new study raises the
possibility of a DNA-based blood test that doctors could routinely
use to determine whether a patient has cancer.
There are many caveats. The research is preliminary, and the
test is not cheap. Even if it does detect cancer, the test -- like
the one currently used to detect prostate cancer -- could raise big
questions about how to deal with the results.
Even so, a genetic test for cancer would be a major advance,
"This would be a way of detecting cancers earlier, and to tell you the level of cancer as you're going through the therapy," said Dr. Victor Velculescu, co-director of the Cancer Biology Program at Johns Hopkins Kimmel Cancer Center in Baltimore.
Several blood tests detect the body's reaction to cancer, and
others are being developed, including one that may spot stray
cancer cells in the blood. This test is unique because it examines
the blood for signs of DNA that's spilled out of cancerous cells
into the bloodstream when they die, Velculescu explained.
In the study, researchers found that the test picked up
differences in 10 patients with breast or colorectal cancer when
compared to 10 healthy patients. The test didn't falsely suggest
any of the healthy patients had cancer, he added.
"We're looking at the entire genome and can apply the test to any cancer type or individual cancer," Velculescu said.
The test costs thousands of dollars, but Velculescu expects the
price would eventually drop.
In the future, he said, the test could be performed at regular
intervals and detect cancer without requiring a biopsy. For now,
however, the test needs to undergo more research.
There's one possible complication: If the test detects signs of
cancer, then what? A blood screening test for prostate cancer,
known as the PSA test, is a topic of hot debate because some
patients may undergo unnecessary treatment.
Still, Dr. Otis Brawley, chief medical officer and executive
vice president of the American Cancer Society, said he can foresee
a cancer screening blood test becoming a routine part of medicine,
although it may take 20 years or more to get there.
In some cases, Brawley said, doctors could potentially choose to
use the screening test to evaluate the extent of cancer in a
patient instead of performing a biopsy. For example, in certain
types of lung cancer, a biopsy can be dangerous because a needle is
inserted into the lung, he noted.
For now, Brawley said, the test is "extremely expensive and
extremely preliminary, and it's probably several years before
anybody's going to be able to buy this."
The study appears in the Nov. 28 issue of the journal
Science Translational Medicine.
For more about
cancer, visit the U.S. National Library of Medicine.
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