Substantial
Improvement in Prostate Cancer PSA Testing Discovered by Genetics Firm
Better results will
prevent unnecessary biopsies, catch more cancers, says deCODE
Dec. 16, 2010 – PSA (prostate specific antigen) testing is the best tool available for
prostate cancer screening but is far from a perfect detective. A high
reading often prompts a biopsy, which too often was not needed, because
no cancer is found. Many of these biopsies may be avoided with a new
discovery by deCODE genetics that improves the accuracy of PSA
tests.
Scientists from
deCODE genetics, Reykjavik, Iceland, and academic colleagues from
Iceland, the UK, US, Netherlands, Spain and Romania report the discovery
of a set of single-letter variations in the sequence of the human genome
(SNPs) that impact individual baseline levels of prostate specific
antigen, or PSA.
Testing for PSA
levels is the most commonly used screening tool for the detection of
prostate cancer. It is approved by the Food and Drug Administration and
annual exams are covered for senior citizens by Medicare.
A prostate
biopsy is routinely recommended for men with PSA above a certain
threshold. However, PSA levels can rise for reasons unrelated to
prostate cancer and baseline healthy levels vary substantially between
individuals, resulting in many men without cancer being biopsied while
cancer in others is not detected.
The paper
published yesterday demonstrates that analysis of four SNPs can be used
to derive a personalized PSA threshold that more accurately identifies
those men who are more likely to have a positive biopsy and for whom one
should therefore be recommended.
About
Prostate-Specific Antigen (PSA) Test
What is the
prostate-specific antigen (PSA) test?
Prostate-specific antigen (PSA) is a protein produced by cells of the
prostate gland. The PSA test measures the level of PSA in the blood. The
doctor takes a blood sample, and the amount of PSA is measured in a
laboratory. Because PSA is produced by the body and can be used to
detect disease, it is sometimes called a biological marker or a tumor
marker.
The U.S. Food
and Drug Administration (FDA) has approved the use of the PSA test along
with a digital rectal exam (DRE)
to help detect prostate cancer in men 50 years of age or older.
Medicare covers
annual PSA test
Currently,
Medicare provides coverage for an annual PSA test for all men age 50 and
older.
Doctors’
recommendations for screening vary. Some encourage yearly screening for
men over age 50, and some advise men who are at a higher risk for
prostate cancer to begin screening at age 40 or 45. Others caution
against routine screening. Although specific recommendations regarding
PSA screening vary, there is general agreement that men should be
informed about the potential risks and benefits of PSA screening before
being tested.
“This is
straightforward genetics with direct clinical utility. Detected early,
prostate cancer can be treated with near total success,” said Kari
Stefansson, CEO of deCODE and senior author on the study.
“The challenge
is to more effectively risk stratify the population, identifying and
biopsying those at high risk and with aggressive disease while
minimizing the number of negative biopsies we perform. And using the
genetics we are improving the sensitivity and specificity of PSA
testing.
“Like virtually
every protein in the body, PSA levels vary between individuals according
to SNPs that regulate gene expression. The SNPs reported today enable us
to personalize PSA thresholds, thereby changing the recommendation on
whether to biopsy for a substantial proportion of men.
“Moreover, the
discriminatory power of testing for these SNPs is highest when done in
tandem with the SNPs associated directly with risk of the disease
measured by our deCODE ProstateCancer™ test. We are working to swiftly
incorporate these PSA markers into our testing portfolio.”
The study was
conducted in several stages and involved tens of thousands of men with
and without prostate cancer.
First, more than
300,000 SNPs were analyzed in 16,000 Icelandic men with PSA measurements
but who had never been diagnosed with prostate cancer. SNPs that
correlated with PSA levels were identified and then validated in a
cohort from the UK.
These SNPs were
then studied in large case-control cohorts from Iceland, the
Netherlands, Spain, Romania and the US to establish the association with
PSA levels independent of risk of prostate cancer itself.
The authors then
demonstrated how measuring four SNPs correlated with PSA levels can be
used to obtain a personalized threshold for when to biopsy, and that
using such thresholds improves the ratio of positive to negative
biopsies. The greatest improvement in prediction accuracy was seen when
men were tested both for the PSA correction SNPs as well as a panel of
prostate cancer risk SNPs detected by the deCODE ProstateCancer test.
The paper,
entitled “Genetic correction of PSA values using sequence variants
associated with PSA levels,” was published online in
Science Translational Medicine and will appear in an upcoming
print edition of the journal.
The work was
funded in part by grant 202059 (PROMARK) and grant 218071 (CancerGene),
both from the 7th Framework Program of the European Union.
About deCODE
(company statement)
Headquartered in
Reykjavik, Iceland, deCODE genetics is a “global leader” in analyzing
and understanding the human genome. Using its unique expertise and
population resources, deCODE has discovered key genetic risk factors for
dozens of common diseases ranging from cardiovascular disease to cancer.
deCODE employs its capabilities to develop DNA-based tests and scans to
better understand individual risk and empower prevention, and partners
its tests, intellectual property and analytical capabilities with
companies and research institutions around the globe.
Through its CLIA-
and CAP-certified laboratory deCODE offers DNA-based tests including
deCODE ProstateCancer™; deCODE MI™ for heart attack; deCODE
BreastCancer, for the common forms of breast cancer; deCODE AF™ for
atrial fibrillation and stroke; deCODE Glaucoma™; and deCODE T2™ for
type 2 diabetes. Through its pioneering personal genome analysis service
deCODEme™, deCODE enables individuals to better understand their risk of
dozens of common diseases and to learn about their ancestry and other
traits. Visit
www.decode.com; for a full range of tests and scans at
www.decodehealth.com; at
www.decodeme.com; and on our blog at
www.decodeyou.com.
More Links to
Reports on Prostate Cancer in SeniorJournal.com Archives
Researchers studied almost 6,000 senior citizens,
suggest patients be informed about the differences and similarities in
expected outcomes, make treatment decisions with an experienced surgeon
-
Feb. 22, 2010
Androgen-deprivation therapy (ADT) may increase
cardiovascular risk, but unclear whether it’s linked to increased death
from heart disease - Feb. 3, 2010
MIRP, especially with robotic assistance, increased from 1% to 40% of radical prostatectomies from 2001 to
2006,despite limited data on outcomes and costs
Sarcosine is better indicator of advancing disease
than traditional prostate specific antigen test (PSA); it is detected in
urine, researchers hopeful simple urine test can be used
Dec. 16, 2010 – PSA (prostate specific antigen) testing is the best tool available for
prostate cancer screening but is far from a perfect detective. A high
reading often prompts a biopsy, which too often was not needed, because
no cancer is found. Many of these biopsies may be avoided with a new
discovery by deCODE genetics that improves the accuracy of PSA
tests. 
