CO E T
prostate, breast and ovarian cancer cured health scientist successfully captured genetic causes
health reporter,London(weastar times/wp/g):::
A national screening programme for prostate
cancer could be introduced by the NHS in the wake of a huge international effort by more than 1,000 scientists to unravel the genetic causes of prostate, breast and ovarian cancer.
The study, the largest ever to look for faulty DNA that drives the cancers, revealed scores of genetic markers that can identify people most likely to develop the diseases at some point in their lives.
Doctors said a simple £5 spit-test based on the markers could provide patients with a personalised "risk profile" for the diseases and pave the way for individually tailored screening, with those most at risk having more regular health checks.
The findings have major implications for the treatment of prostate cancer. A test based on genetic markers for the disease could identify men whose lifetime risk was a staggering 50%, nearly five times the national average.
Ros Eeles, professor of cancer genetics at the Institute of Cancer Research in London described the results as "the single biggest leap forward" in understanding the genetics of the disease.
A screening service could be offered within five years, and would transform medical treatment for the most common cancer among British men. More than 40,000 men a year are diagnosed with prostate cancer in Britain, and nearly 11,000 die from the disease.
Men who are diagnosed with prostate cancer have far greater survival rates when the disease is picked up early. A man diagnosed with early stage prostate cancer has a 95% chance of surviving for five years, but the figure falls to 60% when the disease is spotted later.
Britain has never introduced a national screening programme for prostate cancer because existing tests are not precise enough. For every life saved by a screening programme based on
the common PSA blood test, 12 to 48 men would be treated unnecessarily for disease that would never cause problems in their lifetime.
"Genetic profiling will be able to refine the risks in the population so that we can target screening to those at higher risk," Eeles told the Guardian.
"We hope that within five years we will be able to use this type of technology in the NHS to target screening to those who are most likely to benefit."
Genetic markers are like spelling mistakes in a person's DNA that raise the risk of disease. To find markers for prostate cancer, scientists compared the genetic make-up of 25,000 prostate cancer patients with a similar number of healthy men. They found 23 new faults in DNA that increase the risk of developing prostate cancer. Importantly, 16 of these drive the most aggressive and life-threatening forms of the disease.
While most men carry a small number of the genetic markers for prostate cancer, the 1% with the most genetic faults face nearly a five-fold increased risk of the disease. These men have a one in two chance of developing the disease.
Alan Ashworth, the chief executive of the
Institute of Cancer Research, said the research "changes the game" for applying genetics to the management of prostate cancer. "Screening for different levels of risk now becomes a real possibility," he said.
A similar investigation into breast cancer found 49 new genetic faults that appear to drive the disease. Women who inherit most of these have a 30% chance of developing the disease, more than three times the national average. Some of the faults were only predictive of the most aggressive, and dangerous, form of the cancer, called oestrogen receptor negative breast cancer.
Women who carry
mutations in genes called BRCA are already known to have a substantially higher risk of breast cancer, at around 65%. But the latest study shows that women who have a BRCA mutation, and carry many of the newly-discovered gene defects, are 80% more likely to develop the disease.
In the third part of the project, which involved 130 institutions from around the world, scientists compared the genetic makeup of ovarian cancer patients with healthy women. The study found eight new gene regions that raise the risk of the disease, bringing the known total to 12. Together, these had a marginal effect on cancer risk, raising the lifetime chance of disease from 1.8% to around 4%.
Eeles said a simple test at a GP surgery could be read by a computer to give each patient a personalised risk profile for the disease. Once the tests are available, doctors could improve their accuracy by adding lifestyle factors into the risk assessment. For example, the risk of breast cancer is raised by alcohol and a high fat diet, but lowered by childbearing and breastfeeding.
Trials are now under way to work out the best way to use the tests, and how any screening programmes might work, or be modified where screening already exists.
In the case of prostate cancer, it is not clear at what age men should be tested to determine their risk of the disease. Since prostate cancer usually only develops after the age of 40, a test much earlier might cause unnecessary and prolonged anxiety. It is not clear either whether men who are found to be at high risk should have blood tests or MRI scans, and when doctors should take biopsies.
Tests for breast cancer risk pose similar problems, though screening procedures, such as mammograms, and interventions, from early use of preventative drugs, to a precautionary
operation to remove the breasts, are more established.
The work, led by the Institute of Cancer Research and Cambridge University, was funded by Cancer Research
THE ROYAL ENGLAND and the Wellcome Trust, and published as a series of papers in
Nature Genetics and several other science journals.
While the studies transform what is known about the genetics underpinning the three cancers, in each case, they account for only 40% of the gene faults that must be involved. To discover the rest, which could be many thousands, scientists will need even larger studies, and would involve sequencing a person's entire genetic makeup.
"Hundreds if not thousands of genes are likely to play a role in how cancers start. But by understanding why some people seem to be at a greater risk of developing cancer, we can look towards an era where we can indentify them, and take steps to reduce their chances of getting cancer, or pick up the disease
in its earliest stages," say chief executive of Cancer Research THE ROYAL ENGLAND.
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