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Scientists are reporting progress on a blood test to
detect many types of cancer at an early stage, including some of the most
deadly ones that lack screening tools now. any groups are working on liquid
biopsy tests, which look for DNA and other things that tumors shed into blood,
to try to find cancer before it spreads, when chances of cure are best.
In a study Thursday
in the journal Science, Johns Hopkins University scientists looked to see how
well their experimental test detected cancer in people already known to have
the disease. The blood tests found about 70 percent of eight common types of
cancer in the 1,005 patients. The rates varied depending on the type — lower
for breast tumors but high for ovarian, liver and pancreatic ones.
In many cases,
the test narrowed the possible origin of the cancer to one or two places, such
as colon or lung, important for limiting how much follow-up testing a patient
might need. It gave only seven false alarms when tried on 812 others without
cancer. The test is nowhere near ready for use yet; it needs to be validated in
a larger study already underway in a general population, rather than cancer
patients, to see if it truly works and helps save lives — the best measure of a
screening test’s value. “We're very, very excited and see this as a first
step,” said Nickolas Papadopoulos, one of the Hopkins study leaders. “But we
don’t want people calling up” and asking for the test now, because it’s not
available, he said.
Some independent
experts saw great promise.
“It’s such a
good first set of results” that it gives hope this approach will pan out, said
Dr. Peter Bach, a health policy expert at Memorial Sloan Kettering Cancer
Center who consults for a gene testing company. “Anything close to 50 percent
or 40 percent detection is pretty exciting stuff,” and this one did better than
that, he said. Dr. Len Lichtenfeld, deputy chief medical officer of the
American Cancer Society, was encouraged that the test did well on cancers that
lack screening tests now. If a blood test could find 98 percent of ovarian
cancers at an early stage, as these early results suggest, “that would be a
significant advance,” he said. But he cautioned: “We have a long way to go to
demonstrate its effectiveness as a screening test.”
Testing the test
The test detects
mutations in 16 genes tied to cancer and measures eight proteins that often are
elevated when cancer is present. It covers breast, colon and lung and five
kinds that don’t have screening tests for people at average risk: ovarian,
liver, stomach, pancreatic and esophageal. Prostate cancer is not included. A
blood test already is widely used — the PSA test — but its value for screening
is controversial.
Researchers
tried the new test on people whose cancers were still confined to where it
started or had spread a little but not widely throughout the body. It detected
33 percent of breast cancers, about 60 percent of colon or lung cancers and
nearly all of the ovarian and liver ones. It did better when tumors were larger
or had spread. It did less well at the very earliest stage.
Caveats and next
steps
The test
probably will not work as well when tested in a general population rather than
those already known to have cancer, researchers say. Hopkins and Geisinger
Health System in Pennsylvania have started a study of it in 10,000 Geisinger
patients who will be tracked for at least five years.
The work was
financed by many foundations, the Mayo Clinic, the National Institutes of
Health and Howard Hughes Medical Institute, which provides The Associated Press
with funding for health and science coverage. Many study leaders have financial
ties to gene testing companies, and some get royalties for patents on cancer
detection methods. Researchers say the test could cost around $500 based on
current materials and methods, but the ultimate goal is to commercialize it, so
what a company would charge is unknown.
Other liquid
biopsy news
Also this week,
Taiwan-based CellMax Life gave results on its liquid biopsy test, which looks
for whole tumor cells shed into blood, at an American Society of Clinical
Oncology conference. Researchers tested 620 people getting colonoscopies or
with confirmed colon cancer at a hospital in Taiwan. The company said its test
had an overall accuracy of 84 to 88 percent for detecting cancer or
precancerous growths and a false alarm rate around 3 percent.
The company’s
chief executive, Atul Sharan, said U.S. studies should start this year. The
test is sold now in Taiwan for $500, but should cost around $150 in the U.S.,
he said. Dr. Richard Schilsky, chief medical officer of the oncology society,
said results are encouraging, but the test needs more study, especially to see
if it gives too many false alarms. “The last thing you’d want is a test that
tells you you might have cancer if you don’t,” he said.