Scientists have found a blood test that can detect eight of the most common cancers that are usually only diagnosed when it is too late to fight them.

Key points: Test detects cancer of the ovary, liver, pancreas, oesophagus, bowel, lung, breast

Test detects cancer of the ovary, liver, pancreas, oesophagus, bowel, lung, breast Designed mainly for people over the age of 50

Designed mainly for people over the age of 50 Could one day reduce the number of people dying from cancer in Australia every year

Researchers from the study, published in the Science journal, said the test could become available to patients in the next few years.

It could let doctors know early on whether a patient had cancer of the ovary, liver, pancreas, oesophagus, bowel, lung or breast.

One of the Australian researchers involved in the study, professor Peter Gibbs from the Walter and Eliza Hall Institute, said it was a major step forward.

"For the first time we're seeing potential for a blood test that can screen for many types of nasty cancers that until now we've had to wait until symptoms are diagnosed quite late," he said.

A team of US and Australian researchers trialled the blood test on more than 1,000 cancer patients.

The test, which is sensitive to mutated DNA floating freely in the blood and cancer-related proteins, was able to detect tumours in 70 per cent of those patients on average.

"[The test is] quite sensitive, so it's detected most of the cancers, these early stage cancers that if diagnosed later are almost universally fatal," Professor Gibbs said.

Eight hundred volunteers who had not yet been diagnosed with cancer were also tested.

Professor Gibbs said that not many people were falsely diagnosed with cancer when they did not have it.

"More than 99 per cent of people without cancer had a normal test," he said.

There are already early screening tests for breast and bowel cancer, but Professor Gibbs said the blood test would help diagnose more people at risk.

"We're anticipating pretty much everyone would be happy to have a blood test — whereas everyone is not so keen on having a colonoscopy," he said.

The test has been designed mainly for people over the age of 50, as well as younger people with a family history of cancer.

"As we get older unfortunately the risk of cancer goes up," Professor Gibbs said.

"There's probably also some younger people that for various reasons, [such as] family history, might have a very risk of cancer and might want to start a little bit earlier.

"But probably the major aim would be the population screened from age 50."

He said they hoped the test would become part of a regular check up at least once a year.

Test 'could reduce number of people dying from cancer'

US researchers are now trialling the test on 10,000 more people to examine how effective it is, as well as to help determine how much the test could cost patients in the future.

"The big question's going to be the cost," Professor Gibbs said.

"I suspect currently you're looking at $1,000 or something like that, in terms of what the tests would cost."

But Professor Gibbs said they expected the cost to come down over time as the technology progressed and the number of people being tested rose.

"So hopefully, eventually this will be a few hundred dollars, which puts it in the ballpark of many other tests that we routinely do," he said.

Professor Gibbs said the test could one day reduce the number of people dying from cancer in Australia every year.

Some of the cancer screening tests that already exist, he said, currently reduce the risk of death by up to 50 per cent.

"It's probably going to have a much bigger impact on tumours like pancreas cancer which are almost always diagnosed late, rather than bowel cancer which we pick up a little bit earlier," he said.

"So it's going to vary cancer by cancer, but it should have a major impacts on all the tumour types and reduce cancer deaths in Australia by many thousands."

Professor Gibbs said it could be some years before the test becomes available in Australian clinics.