Doctors may
soon use a new genetic "barcode" blood test - besides normal
screening - to determine how severe a man's prostate cancer is and how urgently
it should be treated.
Researchers
in Britain have discovered distinct genetic signatures for prostrate cancer and
designed an experimental blood test that reads the genetic changes like a
barcode.
The
researchers say the blood test could be used alongside existing PSA
(Prostate-Specific Antigen) screening to determine which men need more
aggressive or immediate treatment.
Screening
and biopsies
For most
men, however, screening often leads to biopsies, which are currently the only
way to predict the aggressiveness of prostrate cancer. But biopsies are
invasive and carry potential complications, according to Johann de Bono, head
of the prostate cancer research team at The Institute of Cancer Research (ICR)
in London.
A blood
test, he argues, would be much easier for patients and potentially more
accurate, and would allow their cancer to be assessed throughout treatment.
"It
can also give information that a biopsy can't, like how a patient's immune
system can [influence] survival," de Bono says.
Prostate
cancer is the second most common cancer in men after lung cancer.
De Bono
refers to prostate cancer as a "very diverse disease." He says some
people can live with it for years without any symptoms, while others find themselves
confronted with an aggressive, life-threatening form.
Distinguishing
different types
The new
blood test would help distinguish the different types and allow doctors to
adjust the treatment accordingly.
De Bono's
team scanned genes in blood samples from 100 patients with prostate cancer at a
London drug development unit jointly run by the ICR and the Royal Marsden NHS
Foundation Trust, and at a cancer center in Glasgow. The group consisted of 69
patients with advanced cancer and 31 patients were believed to have low risk,
early stage cancer.
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Using
complex mathematical statistics, the researchers divided patients into four
groups based on their pattern of gene activity - that's the
"barcode." They measured gene activity by analyzing levels of RNA,
the genetic material that helps turn DNA into proteins.
After
reviewing the patients' progress two-and-a-half years later, the researchers
established that patients in the one group had survived for significantly less
time than those in the other three.
Further
statistical modeling identified nine key active genes that were shared by all
patients in the one group.
Similar US
research findings
The British
scientists then tested another 70 people with advanced cancer in the US and
confirmed that the nine genes could be used to identify patients who ultimately
survived for a shorter time - 9.2 months compared with 21.6 months for patients
without the gene pattern.
The
research team said its gene signature involved a number of genes used by the
body's immune system, suggesting that the immune system is suppressed in men
whose cancer is spreading around their bodies.
In a
separate project, a US team of researchers led by Professor William Oh at the
Tisch Cancer Institute of Mount Sinai School of Medicine indentified a set of
six genes, linked to a more aggressive form of prostrate cancer, in a group of
62 patients.
The gene
signature of the US team divided patients into two groups: one with an average
survival time of 7.8 months and the other 34.9 months.
Both
studies have just been published in the Lancet Oncology.
"The
tests, if validated by results in a larger number of patients, would be
immediately useful in indicating to patients and doctors what the outlook is -
in other words, which patients might survive for a couple of years versus those
for less than a year," says Malcolm Mason, dean of research in life sciences
and health at Cardiff University and a prostate cancer expert with Cancer
Research UK.
'Simple and
inexpensive'
But Mason
is also quick to point out that blood tests will "open the door" to
treatment questions.
"Would
patients with the worst prognosis benefit from more intensive therapy such as
chemotherapy at an earlier stage?" he asks. "And would further
hormone therapy be best used in those with a better prognosis?"
Mason says
these are questions that can't be answered without further clinical trials.
De Bono
describes his team's blood test as "simple and inexpensive" and says
it could be available for routine use in five years.
Mason can hardly wait.
"It
may be that another piece of the jigsaw puzzle has slotted into place,"
Mason says.
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