Until now doctors had no reliable way of telling which men are most at risk

Rapid treatment is vital for men with more aggressive forms of the disease

new method of spotting tumour cells in the blood

A blood test that identifies the deadliest forms of prostate cancer could save thousands of men from unnecessary treatment while ensuring rapid attention for those whose lives are at risk.

The new method of spotting tumour cells in the blood, discovered by researchers at Queen Mary University of London, is in its early stages.

But if initial findings based on tests on 80 samples from men with prostate cancer are confirmed in bigger studies, it could revolutionise treatment.

The new method of spotting tumour cells in the blood is in its early stages. But if initial findings are confirmed in bigger studies, it could revolutionise treatment

Some 47,000 men are diagnosed with prostate cancer in the UK each year but the severity of the disease varies hugely.

Rapid treatment is vital for those with more aggressive forms of the disease, which kills 11,300 men each year.

But if it stays in the prostate and does not spread, it is often best to offer no treatment, an approach known as ‘active surveillance’.

Yet until now doctors have had no reliable way of telling which men are most at risk.

Up to 30,000 have a localised, low-grade form of the disease that has yet to spread beyond the prostate.

But because there is no reliable way to tell how severe it is, about two thirds of them undergo gruelling treatment including radiotherapy, surgery or both.

This can have severe side effects including impotence, incontinence and bowel problems.

In future, testing for circulating prostate cancer cells could help doctors identify high-risk patients who may need radical intervention and spare those at low risk from unnecessary treatment.

The sensitive tests would pick up minute strands of DNA shed by a tumour as it grows. It is one of the first in a battery of ‘liquid biopsies’ that experts think will revolutionise the treatment of cancer.

This approach – called ‘precision medicine’ – enables doctors accurately to target cancers according to their genetic make-up, to closely monitor tumours as they mutate and evolve, and to switch drugs if cancer becomes resistant to a certain treatment.

Rapid treatment is vital for those with more aggressive forms of prostate cancer, which kills 11,300 men each year

Lead scientist Dr Yong-Jie Lu, from Queen Mary’s Barts Cancer Institute, said: ‘Our research shows the number of these specific cells in a patient’s sample is a good indicator of prostate cancer spreading.

‘By identifying these cells, which have gained the ability to move through the body, we have found a potential new way to monitor the disease.

‘If we’re able to replicate these studies in larger groups of people, we may be able to one day predict the risk of someone’s cancer spreading so they can make more informed treatment decisions.’

The findings were presented at a conference of the National Cancer Research Institute in Liverpool.

Dr Iain Frame, of Prostate Cancer UK, said: ‘This research adds to our understanding of what might make prostate cancer cells tick but it’s incredibly early days.