A simple blood test that can detect a cancer before a tumour has taken shape has been developed by British scientists. Due to be introduced in Britain by early next year, it is described as offering a “paradigm shift” in cancer diagnosis.

The test is the first to identify accurately the signals sent out by a person’s immune system as a cancer germinates. Research suggests that such signals can be detected up to five years before a tumour is spotted, priming doctors to intervene at the earliest moment when a solid cancer appears.

Scientists described the test, devised initially for lung cancer, as a means of tackling the country’s poor record of early diagnosis and disease survival. Detection of lung, pancreas and gullet cancers is often so late that it acts as little more than confirmation of imminent death.

Physical symptoms — the most common trigger for treatment — often will not appear until two thirds of the way through the cancer’s development. In the case of lung disease, the tumour can already be the size of a tennis ball. Even the earliest screening detection is only picking up the cancer after more than 20 cell divisions, while death normally comes after about 40.

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