A blood test that could predict prostate cancer more than a decade before diagnosis is a step closer, after scientists discovered a new way to identify men at risk of the disease.
In the largest study of its kind, Oxford University researchers identified 12 proteins in the blood linked to prostate cancer, including seven associated with its most aggressive forms.
Experts say the breakthrough could pave the way for tests that identify men at greatest risk years before symptoms appear – and potentially help prevent deadly forms of the disease from developing in the first place.
There are around 63,000 new prostate cancer diagnoses and 12,000 deaths every year in Britain, the equivalent of one man dying every 45 minutes.
Cases among men under 50 have more than quadrupled in England in just over two decades.
Because early-stage prostate cancer often causes no symptoms, the disease can go undetected until it has spread to other parts of the body, when treatment is more difficult.
Currently, there is no national screening programme for the disease.
Instead, men over 50 can request a prostate-specific antigen (PSA) blood test, although raised levels do not necessarily mean cancer is present.
Prostate cancer could be spotted more than a decade in advance after scientists discovered telltale clues of the disease in the blood
The Daily Mail is campaigning to end needless prostate cancer deaths and for a national screening programme, initially targeting men at highest risk, including black men and those with a family history of the disease or specific genetic mutations.
In the new study, researchers examined blood samples from 2,555 participants, including 982 who later developed prostate cancer and 1,573 who did not.
The team analysed more than 6,000 proteins in the blood and followed participants for around 16 years.
They discovered differences in the blood of men who went on to develop prostate cancer compared with those who remained cancer-free.
Of the 12 proteins linked to the disease, seven were associated with aggressive forms of prostate cancer.
One was ANKRD1, previously linked to cancers more likely to spread to other parts of the body.
Another was GZMK, produced by immune cells that help recognise and destroy abnormal cells, raising the possibility that the immune system may help keep prostate cancer at bay years before diagnosis.
The researchers stressed that the findings do not mean cancer was already present when the blood samples were collected.
Instead, the proteins may provide clues about why some men are more likely to develop the disease.
Professor Karl Smith-Byrne, senior author of the study, said: 'Together with existing and future genetic evidence, these findings may help us identify biological pathways that could be targeted to prevent aggressive prostate cancer.'
However, more research is needed before the proteins could be used in a blood test to reliably predict who will develop prostate cancer.
Professor Prabhakar Rajan, from Queen Mary University of London, who was not involved in the study, cautioned: 'There is missing information on the aggressiveness of some cancers, and some associations may have arisen by chance.'
But Dr Iain Foulkes, executive director of research and innovation at Cancer Research UK, which part-funded the study, said: 'Prostate cancer is one of the biggest cancer killers of men, yet we still don't fully understand why some tumours grow slowly and may never cause harm, while others become aggressive and life-threatening.
'Understanding what drives these differences is crucial if we are to identify those most at risk and ultimately save more lives. This research offers important new clues.
'While there is more work to do, discoveries like this could pave the way for better ways to identify men at risk and, ultimately, prevent aggressive prostate cancer before it develops.'
Dr Zhe Huang, first author of the study and a postdoctoral epidemiologist at Oxford Population Health, said: 'Ultimately, we hope this will help us understand the biology of aggressive prostate cancer and identify markers that could improve how we assess risk in the future.'