A new cancer blood test is being described by British physicians as a "game changer" and "a new era" as a trial has turned up dozens of early-stage, undiagnosed cases.

It's called the Galleri test, and it looks for multiple different kinds of cancer DNA in the blood, which can not only identify cases in much earlier stages, but even where to look in the body to find it.

In the recently-completed Pathfinder Trial, 6,621 adults over 50 took the Galleri blood test, which came back positive in 92 patients, 35 of which already had solid tumors, and none of whom had any early symptoms.

The tumors, found in the liver, colon, breast and blood, were mostly either too small to have been detected normally, or in the case of some others, not of the kind that are routinely tested for, including ovarian and pancreatic, which tend to be diagnosed late and have high mortality.

"Blood tests for multiple types of cancer used to belong in the realm of science fiction, but now they are an area of cancer research that is showing promise for patients," said Naser Turabi, the director of evidence and implementation at Cancer Research UK.

"Research like this is crucial for making progress against late-stage cancers and giving more patients the chance of a good outcome. The Pathfinder trial results give us a better understanding of how frequently cancer is found by this blood test in people who haven't been previously diagnosed."

Next year, a second trial with participants numbering 165,000 are expected to come into the NHS