A CHEAP and simple blood test can diagnose cancer years before symptoms show, scientists claim.
Experts say the non-invasive technique is 90 per cent accurate in detecting five common types of cancer and costs less than £80 per patient.
The researchers, from China, hope it could lead to screening programmes for tumours of the lung, bowel, liver, stomach and gullet.
These types of cancer claim almost 70,000 lives in total in the UK every year.
The technique, called PanSeer, looks for specific chemical changes in the blood, known as methylation.
Lead author, Prof Zhang, of the University of California, San Diego, said: "The material and labour cost is less than $100 (£79)."
It detected cancer in 91 per cent of plasma samples collected from individuals who had no symptoms at the time, according to the findings published in the journal Nature Communications.
They came from 605 patients, 191 of whom were diagnosed with one of the five types - one to four years later.
In addition, the test successfully identified cancer in 88 per cent of the 113 people who had already been diagnosed - and recognised 95 per cent of the healthy samples.
Prof Zhang said: "The survival of cancer patients significantly increases when the disease is identified at early stages, as the tumour can be surgically removed or treated with appropriate drugs.
"However, only a limited number of screening tests exist for a few cancer types."
Professor Kun Zhang said: "The ultimate goal would be performing blood tests like this routinely during annual health checkups."
He likened it to the way in which women are given regular mammograms for breast cancer.
Prof Zhang said: "The five-year survival rate for breast cancer patients is probably the highest among all cancer patients.
"That is mainly due to having mammograms and being able to detect breast cancer early."
He added: "But the immediate focus is to test people at higher risk, based on family history, age or other known risk factors."
The study is unique in that it had access to specimens from a project launched in 2007 involving Chinese patients who had not yet been diagnosed.
Each participant gave blood over a ten year period and underwent regular check-ups with doctors.
This allowed the international team to find cancer markers much earlier than conventional procedures.
They were able to examine samples from both healthy and sick individuals from the same cohort.
Prof Zhang said: "Early detection has the potential to reduce cancer mortality, but an effective screening test must demonstrate asymptomatic cancer detection years before conventional diagnosis in a longitudinal study."
Spot 'asymptomatic' patients
PanSeer is unlikely to predict patients that will go on to develop cancer, Prof Zhang explained.
Instead it is most likely spotting those who already have tumours, but remain asymptomatic.
Prof Zhang added: "Further large-scale longitudinal studies are needed to confirm the potential of the test for the early detection of cancer in pre-diagnosis individuals."
His lab staff have spent more than a decade working on a way to spot cancer based on a biological process called methylation that alters the structure of DNA.
Singlera Genomics, a San Diego and Shanghai based start-up, is now planning to commercialise PanSeer.
Prof Zhang added: "For a commercial test, the cost of getting regulatory approvals and business operation will need to be factored in."
Samantha Harrison, senior early diagnosis manager at Cancer Research UK, said: "Detecting cancers earlier when they are less aggressive and more treatable is crucial, and we're seeing increasingly more accurate blood tests being developed and trialled.
"The PanSeer test has achieved encouraging initial results. Promisingly the test may be able to detect cancer in blood samples taken years before diagnosis.
"But these are early results that now need to be validated in larger studies.
"The next milestone will be to give the test to people who don't have cancer and see if, years down the line, it does spot any new cancers earlier than current methods.
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"If so, we might be one step closer to screening tests for cancers too often diagnosed late.
"In the meantime, if you have noticed a change in your health, or have a symptom that you're worried about, make contact with your GP.
"GPs and hospitals are changing the way they do things to help keep patients, and staff, safe so do get symptoms checked out."