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Science

Gene 'barcode' scans men for prostate cancer

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.

Colombia's President Juan Manuel Santos recently underwent surgery to remove a prostate tumor

Prostate cancer is common in men - Colombia's President Juan Manuel Santos has just undergone surgery to remove a tumor

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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