New Blood Test Significantly Increases Accuracy of
PSA Screening for Prostate Cancer
Greatly reduces false-positives in prostate cancer
screening that often require a biopsy of the gland to check for tumors
May 28, 2009 - Tens of thousands of male senior
citizens may be able to avoid the pain and anxiety of prostate biopsies
if a new blood test that is used in combination with a prostate-specific
antigen (PSA) screening lives up to its early testing that shows a sharp
increase in the accuracy of prostate cancer diagnosis.
The six-gene molecular diagnostic test, when
combined with a PSA test, accurately detected prostate cancer more than
90 percent of the time, say researchers from Dana-Farber Cancer
Institute.
William K. Oh, M.D., and Robert W. Ross, M.D., will
give the report on Sunday at the annual meeting of the American Society
of Clinical Oncology in Orlando.
Earlier studies suggest that the conventional PSA
test is 60-70 percent accurate in detecting cancer.
Men who are found to have elevated levels of PSA in
routine screening tests are often referred for a biopsy of the gland to
check for tumors. Nearly two-thirds of biopsies performed -- a painful
procedure with some risk of complications -- do not find any cancerous
cells.
This high rate of "false positive" PSA test results
underscores the need for a more accurate method for detecting prostate
cancer, said Oh, who is the clinical director of the Lank Center for
Genitourinary Oncology at Dana-Farber.
The two-year study involved 484 participants. The
group comprised 204 men with known prostate cancer, 110 men with benign
prostatic hypertrophy (BPH), and 170 healthy men in a control group. (BPH
can elevate PSA levels in the blood, which often leads to a biopsy to
rule out prostate cancer.) These groups were split into age-matched
training and validation sets.
The researchers sought to measure the accuracy of a
six-gene whole blood RNA transcript-based diagnostic test developed by
Source MDx in Boulder, Colo., both in terms of its sensitivity (the
ability to detect prostate cancer) and specificity (the ability to
identify people who don't have prostate cancer).
Source MDx researchers developed the test after
initially working with a set of 174 candidate genes whose activity was
compared in the different study groups. They narrowed the pool down to
just six genes that, as a group, were highly sensitive in predicting
which patients had prostate cancer and which were normal.
The study found that "the six-gene model was more
accurate than PSA alone at predicting cancer if you had it and no cancer
if you didn't," said Oh. The test's accuracy improved even more when PSA
measurements were added. Combined, the two tests achieved a diagnostic
accuracy of more than 90 percent in specificity and sensitivity and
eliminated most of the false-positives yielded by the PSA test.
Based on these findings, the researchers are
planning to conduct a larger, multicenter clinical trial involving
approximately 1,000 men to determine if the findings remain valid.
"These findings are very encouraging and suggest
that this new test could spare tens of thousands of men from undergoing
an unnecessary biopsy," Oh said.
"However, until we can verify our findings, it is
important to recognize that the PSA test, despite its limitations, is
still the best test available for diagnosing prostate cancer at this
time."
Background Information
The study was funded in part by Source MDx and a
Prostate Cancer SPORE grant at Dana-Farber/Harvard Cancer Center.
Dana-Farber Cancer Institute (www.dana-farber.org)
is a principal teaching affiliate of the Harvard Medical School and is
among the leading cancer research and care centers in the United States.
It is a founding member of the Dana-Farber/Harvard Cancer Center
(DF/HCC), designated a comprehensive cancer center by the National
Cancer Institute.
The findings (abstract #5052) will be discussed at
a poster session of the annual meeting of the American Society of
Clinical Oncology in Orlando on Sunday, May 31, 8-11 a.m., Level 2,
W230A.
Keep up with the latest news for senior citizens, baby
boomers
May 28, 2009 - Tens of thousands of male senior
citizens may be able to avoid the pain and anxiety of prostate biopsies
if a new blood test that is used in combination with a prostate-specific
antigen (PSA) screening lives up to its early testing that shows a sharp
increase in the accuracy of prostate cancer diagnosis.