The NHS has launched the world's largest blood test trial designed to detect more than 50 types of cancer before symptoms appear.

The NHS-Galleri Trial is asking more than 140,000 volunteers aged between 50 and 77 to come forward for the tests, which work by finding chemical changes in fragments of our genetic code.

Participants will be asked to give a blood sample at a locally based mobile clinic; they will then be invited back after one year, and then again after two years, to give further samples.

Research has shown the blood test is particularly effective at finding cancers which are typically difficult to identify early, such as bowel, lung, pancreatic and throat cancers.

The trial is part of the NHS’s Long Term Plan ambition to catch three quarters of cancers at an early stage, when they are easier to treat.

Amanda Pritchard, NHS chief executive, said that the trial could "revolutionise" cancer treatment, as finding cancer before symptoms appear gives patients the “best possible chance of survival”.

"The test could be a game-changer for early cancer detection"

The trial is being run by The Cancer Research UK and King’s College London Cancer Prevention Trials Unit in partnership with the NHS and healthcare company, GRAIL, which has developed the Galleri test.

It is operating with the support of eight NHS Cancer Alliances across England that span Cheshire and Merseyside, Cumbria, Greater Manchester, the North East, West Midlands, East Midlands, East of England, Kent and Medway, and South East London. For the purposes of the trial, only people living these areas will be invited to take part.

Prof Peter Sasieni, Director of The Cancer Research UK & King’s College London Cancer Prevention Trials Unit and one of the trial’s lead investigators, said: “We need to study the Galleri test carefully to find out whether it can significantly reduce the number of cancers diagnosed at a late stage. The test could be a game-changer for early cancer detection and we are excited to be leading this important research.”

Initial results of the study are expected by 2023. If the trial is a success, the tests will then be rolled out to a further one million people in 2024 and 2025.